Vivek Bharti 3M Company
Zhongyang Cheng Auburn University
Qiming M. Zhang The Pennsylvania State University
Yoseph Bar-Cohen Jet Propulsion Laboratory
Gerhard M. Sessler Darmstadt University of Technology
C1: Piezoelectric and Electrets
Danilo De Rossi
Monday AM, November 27, 2006
Room 201 (Hynes)
9:30 AM - **C1.1
Maxwell-Wagner Piezo-electrets: A concept for ``man-made" Dipoles with Bipolar Interface Charges on ``hard" Platelets in a ``soft" Polymer Matrix.
Reimund Gerhard-Multhaupt 1 , Werner Wirges 1 , Ruy Altafim 2 , Ruy Altafim 2 Show Abstract
1 Department of Physics, University of Potsdam, D-14469 Potsdam Germany, 2 Engineering School of São Carlos, University of São Paulo, CEP 13.560 São Carlos (SP) Brazil
Polymer-based piezoelectrics (and pyroelectrics) come in several different types:(1) Semi-crystalline polar polymers such as polyvinylidene fluoride (PVDF) and some of its copolymers exhibit useful piezoelectric coefficients if their “hard” crystalline phase is ferroelectric so that the dipole density within the “soft” amorphous phase changes upon mechanical or electrical stressing (“secondary piezoelectricity”).(2) Micro- or nano-composites of “hard” inorganic ferroelectric particles e.g. from lead zirconate titanate (PZT) or barium titanate (BT) in a “soft” highly insulating polymer matrix exhibit the same dipole-density effect, but also a significant stress dependence of the polarization in the ferroelectric particles (“primary piezoelectricity”).(3) The recently discovered cellular-polymer ferro-electrets contain internal voids with bipolar space charge. When these “man-made” dipoles are mechanically or electrically deformed, direct and inverse piezoelectricity is observed (a new variant of “primary piezoelectricity”).Here, we introduce a further concept: “Hard” disks (platelets) of an inorganic dielectric such as e.g. silicon dioxide or mica are dispersed in a “soft” highly insulating polymer matrix, and bipolar charge layers are deposited at the internal interfaces between the two components. This concept is an extension of the previously demonstrated two- and multi-layer sandwiches of “soft” and “hard” dielectrics with interface charges.In contrast to the cellular ferro-electrets, the “man-made” dipoles of the new piezo-electrets are the “hard” phase so that the material exhibits essentially only “secondary piezoelectricity” (dipole-density effect). In contrast to the polymer composites with inorganic ferroelectric particles, the dipoles of the new piezo-electrets are made of interface charges. An electric polarization from such interface charges has long been known as Maxwell-Wagner polarization, but is usually not considered to be useful. Consequently, the new materials, whose applications-relevant properties are based on this often un-wanted polarization, may be called “Maxwell-Wagner piezoelectrets”.As a proof of concept, we will report first experimental results on a materials system of mica platelets inserted between thermally fused fluoropolymer films. Known simple models of heterogeneous space-charge electrets will be employed in order to predict the piezoelectric properties of the new composites. Additional possibilities for implementing the new concept will be discussed, and the expected engineering properties of the new piezo-electrets will be compared with those of other piezoelectric materials.
10:00 AM - **C1.2
New Biopolymer Composite With Piezoelectric Properties.
Dawnielle Farrar 1 , Michael Yu 1 , James West 1 , Ilene Busch-Vishniac 1 Show Abstract
1 , Johns Hopkins University, Baltimore, Maryland, United States
10:30 AM - C1.3
Finite Element Modeling of Smart Polymer Based Piezoelectric Composites.
Ronit Kar-Gupta 1 , Christian Marcheselli 1 , T. Venkatesh 1 Show Abstract
1 Mechanical Engineering, Tulane University, New Orleans, Louisiana, United States
10:45 AM - C1.4
Domain Imaging of LB PVDF Copolymers by Piezoresponse Force Microscopy.
Brian Rodriguez 1 , Stephen Jesse 1 , Sergei Kalinin 1 , Jihee Kim 2 , Stephen Ducharme 2 Show Abstract
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska, United States
High quality Langmuir-Blodgett (LB) Polyvinylidene fluoride (PVDF) thin films are widely used as an electroactive material for all-polymer field effect transistors, polymer ferroelectric random access memories and tunneling barriers, data storage and flexible ferroelectric electronic components. In order to realize the full potential of PVDF for these applications, significant progress must be made in nanoscale characterization of the structure and domain dynamics of PVDF LB films.Here, we employ piezoresponse force microscopy (PFM) to image the local piezoelectric response of ultrathin ferroelectric PVDF copolymer films. In PFM, a bias is applied to a conducting atomic force microscope tip in contact with the sample surface. The applied field will cause a piezoelectric material to deform, and this deformation can be measured by monitoring the tip-deflection. In this manner, the local electromechanical properties can be mapped out on the nanoscale. PFM imaging of PVDF thin films reveals ferroelectric domain sizes of less than 50 nm at a resolution below 5 nm. The combination of vertical and lateral PFM data suggests a predominantly vertical orientation of PVDF molecules in 10 ML-thick LB films. The film structure can also be strongly affected by tip-surface forces, and pressure induced modification of film structure is illustrated. The effects of annealing conditions and number of LB monolayers on electromechanical properties are addressed. Ferroelectricity is observed in 2 ML films. In addition, initial results on the temperature dependence of topography and piezoelectric activity is discussed.Research sponsored by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC. Work at the University of Nebraska was supported by the Nebraska Research Initiative and the National Science Foundation.
11:30 AM - **C1.5
From Dielectric Elastomers to Piezo- and Ferroelectrets - Electromechanically Active Soft Matter Materials.
Siegfried Bauer 1 Show Abstract
1 Soft Matter Physics, Johannes Kepler University, Linz Austria
Dielectric elastomers, as well as piezo- and ferroelectrets are soft matter materials characterized by a small Youngs modulus on the order of 1 MPa. They respond in distinct ways to a mechanical or electrical stimulus. Dielectric elastomers change their shape according to Maxwell stress, whereas piezo- and ferroelectrets change shape due to the piezoelectric effect. Dielectric elastomers can therefore be used whenever large and complex three dimensional actuation modes are desirable, whereas piezo- and ferroelectrets show promise as sensitive piezoelectric sensor materials. Recent examples of unusual applications are minimum energy actuators based on dielectric elastomers, as well as flexible field effect transistor switches and microphones made by combining flexible electronics and piezoelectrets in electret field effect transistors. Soft piezoelectrets have been shown to respond both to static and dynamic pressure changes, a clear advantage in comparison to traditional piezoelectric materials. Work supported by the Austrian Science Funds. The author gratefully acknowledges stimulating discussions with Guggi Kofod, Mika Paajanen, R. Gerhard-Multhaupt, S. Bauer-Gogonea, I. Graz and R. Schwoediauer.
12:00 PM - **C1.6
Poling of Thermally Stable Ferroelectrets
Heinz von Seggern 1 , Zhongming Hu 1 , Sergej Zhukov 1 Show Abstract
1 Institute of Materials Science, Darmstadt University of Technology, Darmstadt Germany
Considerable attention has been focused on the investigation of porous nonpolar polymers such as cellular polypropylene (PP) for use as novel piezoelectric materials. The pores, when properly charged, are responsible for a high piezoelectric response. Charging is performed by a modified corona triode which is able to raise the surface potential of the polymer up to a point where electrical breakdown in the pores commences. Under the electric field the breakdown induced charges of opposite sign are separated and trapped at the opposing inner surfaces of the voids. The breakdown process can be monitored by the emitted breakdown-induced light and the resulting charging currents. The different mechanical compliances of the polymer and the air in the voids generate upon mechanical stress a large displacement of the trapped charges by compression of the pores. This induces a change in the polarization and a piezoelectric effect. Unfortunately the generated charges in PP are thermally not stable preventing a large scale application. A solution for the poor thermal stability is offered by using a sandwich structure of a central fibrous polytetrafluoroethylene film (ePTFE) and two adjacent electrically blocking fluoroethylene-propylene (FEP) films. When properly prepared, sufficient charge stability has been reported. An investigation of a single ePTFE layer reveals a small quasi-static piezoelectric d33 coefficient of up to 20pC/N. The reason can be seen in the open-pore structure of the film. Breakdown induced charges generated in the bulk can migrate to the surfaces of the film (breakdown-induced conductivity) where they are compensated by charges on the metal electrode or by charges from the corona plasma . It will be demonstrated that this disadvantage of the single ePTFE film can be utilized when sandwiched between two electrically blocking FEP films . The dynamics of the poling of the individual ePTFE layer and the sandwich will be monitored through the electrical charging currents and through the emitted light of the electrical breakdown. The emitted light allows one to determine the dynamics of charge generation during breakdown and the currents allow one to monitor the temporal behaviour of charge separation and polarization build-up within the ePTFE sandwich. Special attention will be paid to the derivation of the appropriate poling conditions for a sufficient thermal stability in conjunction with a large piezoelectric coefficient. The thermal stability will be investigated by thermally stimulated current (TSC) analysis which allows one to determine the activation energies and to estimate the lifetimes of the piezoelectrets. Z. Hu, H. von Seggern, “Air-breakdown charging mechanism of fibrous polytetrafluoro-ethylene films ,” J. Appl. Phys. 98, 014108 (2005). Z. Hu and H. von Seggern, “Breakdown-induced polarization buildup in porous fluoropolymer sandwiches: a thermally stable piezoelectret” J. Appl. Phys. 99, 024102 (2006).
12:30 PM - C1.7
Electroactive Behavior of a New Nanostructured Polymer
Ravi Shankar 1 2 , Tushar K. Ghosh 2 , Richard Spontak 1 3 Show Abstract
1 Materials Science & Engineering, North Carolina State Un iversity, Raleigh, North Carolina, United States, 2 Fiber and Polymer Science Program, North Carolina State University, Raleigh, North Carolina, United States, 3 Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
Electroactive polymers (EAPs) are emerging as a new class of actuator materials with displacement capabilities that cannot be matched by rigid, striction-driven ceramics. These EAP-based actuators enjoy considerable advantages over other actuators in that they are lightweight, and they exhibit higher energy density, greater resilience, higher response speed, and, maybe most importantly, scalability. The most widely used dielectric EAP is a commercial acrylic foam due to its uncharacteristically high maximum actuation strain in an electric field. However, several drawbacks are associated with this material: it is very tacky and its properties cannot be readily tailored in terms of composition. The present work describes the design of a multifunctional nanostructured polymer system from the ground-up as an EAP. The system consists of incompatible block copolymers that microphase-separate into well-defined nanostructural elements, thereby providing a highly tunable avenue to desired material properties. Copolymer systems varying in molecular weight and composition have been fabricated, and their mechanical and electrical properties have been evaluated. Ultrahigh areal actuation strains (>200%) at significantly reduced electric fields (<40 kV/mm) have been recorded. The hysteresis behavior of these EAP materials has been measured under cyclic loading/unloading at constant strain and compare favorably relative to the acrylic foam. All the copolymer systems investigated here exhibit superior hysteresis behavior compared to other EAP materials reported thus far. In fact, nonrecoverable strain is entirely absent in some of the systems developed during the course of this study, indicating that the nanostructured polymer design could yield new and competitive materials for soft, reliable and robust actuators.
12:45 PM - C1.8
Simultaneous Stretching and Static Electric Poling of PVDF-HFP Copolymer Films.
Huan Yan 1 2 , Liu Yayan 1 , Yang Yifei 1 2 , Wu Yanan 3 Show Abstract
1 Green Chemistry And Process Labratory, Changchun Institute of Applied Chemistry Chinese Academy of Science, Changchun China, 2 , Graduate School of Chinese Academy of Sciences, Beijing China, 3 Materials Science and Engineering, Jilin University, Changchun China
C2: New Concepts/Materials and Optics
Monday PM, November 27, 2006
Room 201 (Hynes)
2:30 PM - **C2.1
Strain Amplification for Artificial Muscles and Sensors Using Giant Poisson Ratios and Giant Linear Compressibilities.
L. Hall 1 , V. Coluci 2 , D. Galvao 2 , M. Zhang 1 , M. Kozlov 1 , A. Zakhidov 1 , S. Shah 3 , R. Raj 3 , A. Dalton 4 , J. Madden 5 , T. Mirfakhrai 5 , G. Spinks 6 , G. Wallace 6 , J. Barisci 6 , S. Dantas 7 , E. Munoz 8 , Ray Baughman 1 Show Abstract
1 The NanoTech Institute, University of Texas at Dallas, Richardson, Texas, United States, 2 , Universidade Estadual de Campinas, Campinas SP Brazil, 3 , University of Colorado at Boulder, Boulder, Colorado, United States, 4 Physics, University of Surrey, Guildford United Kingdom, 5 , University of British Columbia, Vancouver, British Columbia, Canada, 6 , University of Wollongong, Wollongong, New South Wales, Australia, 7 , Departmento de Fisica UFJF CEP, Minas Gerais Brazil, 8 , Instituto de Carboquimica, Zaragoza Saint Kitts and Nevis
3:00 PM - C2.2
Chemo-electrical energy conversion of Adenosine triphosphate in a Biological Ion Transporter.
Vishnu Baba Sundaresan 1 , Donald Leo 1 , Brian Goode 1 Show Abstract
1 Mechanical Engineering Department, Virginia Tech, Blacksburg, Virginia, United States
Ion transport in cells maintains life functions in plants and animals. The transport across cell membranes occurs through pathways called ion channels and ion pumps. The channels and pumps embedded in a the cell membrane are proteins which respond to different stimulus like concentration gradients, energy from chemical reactions, light and transmembrane potential. The AtSUT4 protein used in our experimental demonstration is a proton-sucrose co-transporter common in Arabidopsis thaliana. Our [Sundaresan and Leo] previous work presented in SPIE Smart Structures conference, San Diego [Mar 2005, Mar 2006], International Mechanical Engineering Congress and Exposition, Orlando [Nov, 2005] and MRS Spring Meeting, San Francisco [Apr, 2006] on fluid transport through AtSUT4 demonstrated the ability to form a bilayer lipid membrane from purified 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine (POPE) phospholipids on a porous substrate and reconstitute the transporter in the membrane. The AtSUT4 used in our experimental demonstration is provided to us by Dr. John Cuppoletti in the College of Medicine, University of Cincinnati. This article focusses on proton transport through the reconstituted AtSUT4 triggered by the biochemical reaction starting from Adenosine triphosphate (ATP) in the presence of ATP-phosphohydrolase enzyme. The proton current resulting from the biochemical reaction can be channeled out of the system to result in electric current. In this article, we present the ability to generate the proton current through the transporter and analyze the parameters affecting the generated current. The ion pump is found to be a constant current power source with an internal resistance of 50-100 kOhms and produces a peak power of 75 nW starting from ATP. The paper will discuss the method to reconstitute the ion transporter on a porous substrate (Lead silicate glass) with the ATP-ase enzyme and the experimental setup to generate electrical power starting from ATP. The paper also discusses an electrical model to determine the ion current through the pump that identifies the parameters that can be tuned to increase the efficiency of the chemo-electrical energy conversion process. This discussion will be followed by a simple demonstration of a sensor application that can be directly powered from the power source.
3:15 PM - C2.3
Two-phase Core/Polymer Shell Microcapsules Prepared by In Situ Polymerization for Electrophoretic Image Displays.
Ru Qiao 1 , Young Soo Kang 1 Show Abstract
1 Department of Chemistry, Pukyong National Univ., Pusan Korea (the Republic of)
4:30 PM - C2.4
Nanocomposite with Very Large Electro-optic Effect and Widely Tunable Refractive Index.
Qin Chen 1 , Minren Lin 2 , Jonathan Lee 1 , Qiming Zhang 1 , Shizhuo Yin 1 Show Abstract
1 Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania, United States, 2 Materials Research Lab, Pennsylvania State University, University Park, Pennsylvania, United States
4:45 PM - C2.5
Thermally Tunable Bandgap in Polymer Photonic Crystal
Magdalena Nawrocka 1 , Tao Liu 1 , Roberto Panepucci 1 Show Abstract
1 Electrical and Computer Engineering, Florida International University, Miami, Florida, United States
5:00 PM - C2.6
Fundamental Understanding of the van der Waals – London Dispersive Interactions Of Polymers From Optical Properties Determined Using Vacuum Ultraviolet Spectroscopy
Roger French 1 2 , K. Winey 2 , M. Yang 1 , Weiming Qiu 1 Show Abstract
1 , DuPont Central Research, Wilmington, Delaware, United States, 2 Materials Science, University of Pennslyvania, Philadelphia, Pennsylvania, United States
The London dispersion interaction is a universal component of the long-range van der Waals interaction and arises from the transient induced dipoles, i.e., the interatomic bonds of the electronic structure of materials and their optical properties. Dispersion interactions play a role in interface and surface energies, wetting, the formation and stability of surficial and interfacial films, flocculation of colloidal systems, and force microscopy, and have increased importance in the nano-scale sciences due to their long range nature. We study the interband optical properties of polymers in the vacuum ultraviolet (VUV) region from 1.5 to 32 eV. The quantitative optical properties exhibit electronic transitions which we assign to three groupings, E1, E2 and E3, corresponding to a hierarchy of interband transitions of aromatic (pi->pi*), non-bonding (n->pi*,n->sigma*), and saturated (sigma->sigma*) orbitals. In polystyrene, for example, we see strong features in the interband transitions arising from the side chain pi bonding of the aromatic ring consisting of a shoulder at 5.8 eV (E1’) and a peak at 6.3 eV (E1) and from the sigma bonding of the C-C backbone at 12 eV (E3’) and 17.1 eV (E3). Lifshitz quantum electrodynamics and full spectral optical properties permit the calculation of the Hamaker constants of the van der Waals-London dispersion interactions and the dispersive component of the surface free energy, critical to many wetting phenomena. Comparison of the total surface free energy and polarity of polystyrene (as determined from Fowkes method contact angle measurements of liquids) with the literature values suggests that the Lifshitz approach, using full spectral Hamaker constants, is a more direct determination of the dispersive component of the surface free energy of polymers. With recent developments in the calculation of full spectral Hamaker coefficients for complex multilayer and graded configurations, the ability to determine, design and control long range interactions in complex systems is being addressed.
5:15 PM - C2.7
Highly Ordered Polymer Films of an Amphiphilic, Regioregular Polythiophene Derivative
Jusroop Mattu 1 , Thomas Johansson 1 , Steven Holdcroft 1 , Gary Leach 1 Show Abstract
1 Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
The fabrication and characterization of highly ordered thin films made from amphiphilic, regioregular polythiophene derivatives are described. Films of poly(3-(11-(2-tetrahydropyranyloxy)undecyl)thiophene (PTHPUDT) were prepared by the Langmuir Blodgett technique. The amphiphilic nature of the polymer affords layer-by-layer deposition and the formation of multilayer films of head-to-head and tail-to-tail, Y-type structure. X-ray diffraction studies indicate bilayer separations of ~30 Å. Anisotropic optical absorption in the plane of the film indicates that the thiophene backbones are preferentially oriented along the dipping direction. Further, polarized light microscopy studies indicate that these films are highly birefringent and that the optical retardation is uniform over the entire film. Ellipsometry studies confirm the sizable magnitude of the birefringence. Optical second harmonic generation studies of multilayer films provide information regarding both the thiophene orientation within the film and the anisotropic distribution of chromophores in the surface plane. Taken together, this data offers strong evidence of highly ordered films in which the hydrophobic polythiophene chains lie parallel to the substrate surface with their alkyl chains oriented normal to the surface as dictated by the hydrophilic nature of the alkyl chain’s terminal tetrahydropyran functional group. As such, these films offer the potential for elucidating the connection between polymer morphology and physical property in materials that are otherwise subject to a sufficiently complex distribution of morphologies that such a correspondence is precluded.
5:30 PM - C2.8
Ionic Self-Assembled Organic Nonlinear Optical Films for Electro-optic Devices.
Cemil Durak 1 , Akhilesh Garg 2 , Kai Chen 1 , Hans Robinson 1 , Rick Davis 2 , Harry Gibson 3 , James Heflin 1 Show Abstract
1 Dept. of Physics, Virginia Tech, Blacksburg, Virginia, United States, 2 Dept. of Chemical Engineering, Virginia Tech, Blacksburg, Virginia, United States, 3 Dept. of Chemistry, Virginia Tech, Blacksburg, Virginia, United States
Organic electro-optic (EO) modulators have the potential for operation at higher modulation frequency (>100 GHz) at lower voltages (<1 V) and at lower cost than their currently employed inorganic counterparts. In order to achieve these properties, organic nonlinear optical (NLO) materials must contain polarizable molecules that are arranged noncentrosymmetrically, e. g., dipole moments aligned in the same direction. One approach for achieving the polar order required for second order nonlinear optical effects in organic thin films is the fabrication of ionic self-assembled multilayers (ISAMs). This method is simple, rapid and inexpensive. Although ISAM films yield high thermal and temporal stability, their NLO performance was poor due to limited polar ordering. A recent variation on ISAM films, hybrid covalent/ionic assembly, provides an even higher degree of polar order by alternating between covalent and electrostatic deposition of layers, controlled by the pH of the oppositely charged immersion solutions. These films are exceptionally homogeneous and exhibit excellent temporal (>3 years) and thermal (>24 hours at 150 C) stability. Highly stable thin films with electro-optic coefficients greater than 20 pm/V (2/3 of that of lithium niobate) have been fabricated by this approach. Using robotic deposition equipment, ISAM films greater than 700 nm thick have been fabricated with excellent linearity of absorbance and quadratic dependence of second harmonic intensity on the number of bilayers. In addition, the chromophore density, tilt angle, and nonlinear susceptibility can all be improved by addition of salt to the deposition solutions in order to reduce the repulsive interactions of the chromphores as the adsorb on the film surface. Furthermore, silver nanostructures have been deposited on NLO ISAM films by nanosphere lithography. Using the plasmonic field enhancement provided by the metallic nanostructures, additional increases in the nonlinear optical susceptibility of more than 100x have been achieved.
C3: Poster Session: Smart Dielectric Polymers
Monday PM, November 27, 2006
Exhibition Hall D (Hynes)
9:00 PM - C3.1
Radiation Dose Dependence of the Relaxor Ferroelectric P(VDF-TrFE) Copolymers Exposed to UV Radiation.
Cezar Welter 2 , Roberto Moreira 2 , Luiz Faria 1 Show Abstract
2 Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, 1 Materiais e Combustivel Nuclear, Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, MG, Brazil
9:00 PM - C3.10
Energetics of a Wavy Crack in a low-k Dielectric Film Confined by Elastic Substrates.
Jae-Hyun Kim 1 2 , Youbo Lin 1 , Joost Vlassak 1 Show Abstract
1 DEAS, Harvard University, Cambridge, Massachusetts, United States, 2 Nano-mechanical system research center, Korea Institute of Machinery and Materials, Daejeon Korea (the Republic of)
Wavy cracks are often observed in sandwiched layers during fracture toughness test or thin film fabrication process, and they can be classified in several types  depending on the configuration. Recently, a wavy crack has been observed in a low-k dielectric film (organosilicate glass) sandwiched by two silicon substrates during four-point bend tests. The wavelength is 20 to 40 times larger than the film thickness and the crack path alternates between the bulk of the film and the OSG/barrier interface. There are several papers in the literature that try to explain and predict the path of a wavy crack based on a crack path selection law and a crack path stability criterion. The conventional crack path selection law  relies on an accurate calculation of the stress state at the crack tip. This approach leads to computationally intensive numerical simulations of cracked bodies. Since the results of these simulations depend sensitively on the geometry, the material combination and the loads applied to the cracked body, the results of existing simulations in the open literature cannot be directly applied to the wavy crack problem of interest. In this study, the energetics of a wavy crack is studied to enhance our fundamental understanding of wavy crack propagation. The effects of geometry (film thickness), material constants and applied loads (including residual stress) on the wavelength of the crack are explored using a first order perturbation analysis of a wavy film on an elastic substrate. The critical wavelength is determined, for which a wavy crack is energetically favored over a straight crack, and the expression for the most preferred wavelength is also derived. An analysis based on a global energy minimum may sometimes be misleading since there can be several local minimum states during the fracture process; this is why an analysis based on a crack path selection law is generally preferred. The results of the current analysis are compared with those obtained using a local crack path selection criterion and are applied to explain the experimental observations of wavy crack patterns in low-k dielectric layer.References A.R. Akisanya and N.A. Fleck, “Brittle fracture of adhesive joints,” International Journal of Fracture 58, pp. 93-114, 1992. J.W. Hutchinson and Z. Suo, “Mixed mode cracking in layered materials,” Advances in applied mechanics 29, pp. 63-191, 1992.
9:00 PM - C3.11
Compact Polymer Actuators applied in Refreshable Braille Display Using P(VDF-TrFE-CFE) terpolymers
Sheng Liu 1 2 , Kailiang Ren 1 2 , Minren Lin 2 , Donald Natale 1 , Qiming Zhang 1 2 Show Abstract
1 Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Materials Research Inititute, The Pennsylvania State University, University Park, Pennsylvania, United States
High strain level and large elastic modulus of electrostrictive P(VDF-TrFE-CFE) terpolymers are developed to make compact polymer actuators. The large electric field induced strain (>5%) and stress level (>20 MPa) with fast response speed offered by the electrostrictive PVDF based polymers provide great opportunity to fabricate compact Braille actuators which can generate large tip motion (~1mm) and several gm force with small size(diameter <2mm, length~45mm), as required for full page Braille display and graphic display, which are still dreams for many blind and vision-impaired. This paper demonstrates the process of fabrication, from film making to actuators testing and control circuit design. Also modeling of actuators movement is presented. Such a compact and robust actuator can directly replace the piezoceramic bimorph actuator and make it possible to produce refreshable Braille display for full page and graphic display, which has more advantages than nowadays single line Braille display.
9:00 PM - C3.12
Femtosecond Laser Micromachining in Azopolymer Films.
Loren Cerami 1 , Cleber Mendonca 1 2 , Tommaso Baldacchini 1 , Eric Mazur 1 Show Abstract
1 Division of Engineering and Applied Sciences and Department of Physics, Harvard University, Cambridge, Massachusetts, United States, 2 Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil
9:00 PM - C3.13
Non-volatile Memory Based on Organic Field-Effect Transistors Using Chargeable Polymeric Gate Dielectrics
Kang-Jun Baeg 1 , Yong-Young Noh 2 , Jieun Ghim 1 , Seok-Ju Kang 1 , Hyemi Lee 1 , Dong-Yu Kim 1 Show Abstract
1 Heeger Center for Advanced Materials (HCAM), Dept. of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju Korea (the Republic of), 2 OE Group, Cavendish Laboratory, University of Cambridge, J J Thompson Avenue, Cambridge CB3 0HE United Kingdom
Many attempts have been made to realize the ideal memory devices comprised of new, fast, non-volatile, and inexpensive ways of storing information. Organic memory has attracted a great deal of interest because of its unique advantages in combination with recent remarkable progress in organic electronics. In ways to create a novel organic memory, several types of memory devices based on organic and polymeric materials have been evaluated. Among these types of organic memory devices, a memory element based on the field-effect transistor (FET) is especially attractive because of its non-destructive read-out and single transistor application. While the OFET memory has many potential advantages, state-of-the-art results of OFET memory devices are positioned at a lower level as compared to other types of organic memories. Furthermore, details of the operating mechanisms of these devices are not well understood. We fabricated an OFET memory device based on pentacene using an additional polymeric gate dielectric layer which had charge trapping ability, refer to as an electret. This device showed excellent non-volatile OFET memory characteristics. Detailed reasons for these results and a possible operating mechanism for our OFET memory device will be discussed.
9:00 PM - C3.15
Novel Branched Structures for Optical and Electronic applications.
Meng Guo 1 , Theodore Goodson 1 Show Abstract
1 , University of Michigan-Ann Arbor, Ann Arbor, Michigan, United States
Organic materials are important for a variety of optical and electronic applications. New materials which show intermolecular excitations within a macromolecular framework may be useful for enhanced effects which are important to light harvesting, nonlinear optical, quantum optical, and electronic applications . We present the approach of the use of all organic materials for the purpose of dielectric effects at relatively high frequencies (> 1 KHz). The use of branched structures for this purpose will be presented. The electronic and optical properties of a number of branched systems will be described. The use of capacitance, steady state adsorption and emission, time-of-flight, ultra-fast time-resolved fluorescence, and EPR spectroscopy to characterize these new and important materials will be presented. The key issue here is that we show the branched macromolecular architecture allows for new properties which are different from their linear analogs. These novel materials serve as a new approach toward enhanced optical and electronic applications.
9:00 PM - C3.16
Cylindrical Optical Waveguide Based Detection And Characterization Of Protein-Anti Protein Binding Events.
Vijay Sekhar Reddy Kovvuri 1 , Shalini Prasad 1 , Sudhaprasanna Kumar Padigi 1 , Ravi Kiran Kondama Reddy 1 , Andres LaRosa 2 , Kofi Asaante 2 Show Abstract
1 Electrical and Computer Science, Portland State University, Portland, Oregon, United States, 2 Department of Physics, Portland State University, Portland, Oregon, United States
9:00 PM - C3.17
Enzymatic Synthesis of Polypyrrole Films and Colloids.
Edgar Amaro 1 , Layza Arizmendi 2 1 , Maria Nicho 1 , Jorge Romero-Garcia 2 , Rodolfo Cruz-Silva 1 Show Abstract
1 Laboratorio de Polimeros, Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Cuernavaca, Morelos, Mexico, 2 Materiales Avanzados, Centro de Investigacion en Quimica Aplicada, Saltillo, Coahuila, Mexico
9:00 PM - C3.18
Manufacturing and Performance Evaluation of Organized Carbon Nanotube-Parylene Multi-Functional Active Thin-Films.
MyungGwan Hahm 1 , Selvapraba Selvarasah 2 , Ernesto Lopez 1 , Chia-Ling Chen 2 , Yung Joon Jung 1 , Mehmet Dokmeci 2 , Sinan Muftu 1 Show Abstract
1 Department of Mechanical Engineering, Northeastern University, Boston, Massachusetts, United States, 2 Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts, United States
9:00 PM - C3.19
Influence of CNT on the Crystallization Behavior of P(VDF-CTFE) Copolymers
Xiaobing Shan 1 , Suiqiong Li 1 , Xin Yang 1 , Zhongyang Cheng 1 Show Abstract
1 Materials Research and Education Center, Auburn University, Auburn, Alabama, United States
9:00 PM - C3.2
Electrical and Microstructural Changes of β-PVDF under Different Processing Conditions by Scanning Force Microscopy
Senentxu Lanceros-Mendez 1 , J. Serrado Nunes 1 , V. Sencadas 1 , M. Belsley 1 , H. Beige 2 , A. Kouvatov 2 , P. Vilarinho 3 , A. Wu 3 Show Abstract
1 Physics, University of Minho, Braga Portugal, 2 Physics, Martin-Luther-University Halle-Wittenberg, Halle Germany, 3 Ceramic and Glass Engineering, University of Aveiro, Aveiro Portugal
Poly vinylidene fluoride (PVDF) has been widely investigated due to its important pyro- and piezoelectric properties. These properties have found various applications, especially as sensor and actuators. The existence and optimization of these properties is intimately related with the fraction of the polymer in the crystalline phase, its structure, microstructure and orientation. All of these in turn heavily depend on the processing conditions. PVDF is a semi-crystalline polymer which shows polymorphism and is commonly crystallized in non-polar crystalline β-phase. The piezo- and pyroelectric properties mainly depend on the β-phase, so that increasing β-phase content has always been of great concern in this field.β-phase can be obtained by mechanical stretching of α-phase films at a given temperature  or directly from solution . Conversion of α into β-phase takes place at stretching temperatures below 100 °C, at a stretch ratio of about 3–5. Nevertheless the achieved amount of β-phase in the crystalline fraction of the material is never 100%. In the films obtained from solution, 100% beta phase films can be achieved in either a porous or non-porous form. The degree of crystallinity is also larger for the samples obtained from solution.This work is mainly devoted to the study of the variations in the topological morphology and piezoelectric domain response of β-PVDF prepared by the aforementioned methods by scanning force microscopy in a piezo-response mode. The effect of poling will also be discussed. Clear differences in the domain distribution and size, as well as in the local piezoactivity, have been identified amongst the different samples. Especially interesting is the piezoactivity of the porous β-phase samples, as they can be useful in biotechnological applications. The differences in the topological and domain morphologies will be correlated with variations that occur in the macroscopic dielectric and piezoelectric response of the material. In addition the changes at a molecular level will explored through far infrared spectroscopy. The authors thank the Portuguese Foundation for Science and Technology (FCT) for financial support (Grant POCI/CTM/59425/2004). V. Sencadas also thanks the FCT for the PhD Grant (SFRH/BD/16543/2004).[1.] V. Sencadas S. Lanceros-Mendez; R. Gregorio-Filho; A.S. Pouzada,Materials Science Forum, Volume 514 – 516, p. 872, 2006[2.] V. Sencadas, R. Gregorio Filho and S. Lanceros-Mendez, Journal of Non-Cristalline Solids, 352, p 2226, 2006.
9:00 PM - C3.20
Multiple Relaxations in Poly (p-hydroxybenzoic acid-CO-ethylene terepthalate) Liquid Crystal Polymer: TSD Current Investigations.
Jitendra Quamara 1 , Sridharbabu Yarramaneni 1 , Geetika Goyal 1 Show Abstract
1 Physics, National Institute of Technology, Kurukshetra, Haryana, India
9:00 PM - C3.21
Influence of the Crystallisation Kinetics on the Microstructural Properties of α-PVDF.
Marco Silva 1 , Vitor Sencadas 1 , Anabela Rolo 1 , Ana Machado 2 , Senentxu Lanceros-Mendéz 1 Show Abstract
1 Physics, Universidade do Minho, Braga, Braga, Portugal, 2 IPC, IPC - Instituto de Polímeros e Compósitos, Universidade do Minho, Guimarães Portugal
9:00 PM - C3.3
High Piezoelectric d31 Coefficient in Poly(vinylidene fluoride – hexafluoropropylene) Copolymers and its Nanocomposites.
Bret Neese 1 3 , Baojin Chu 1 3 , Xin Zhou 2 3 , Sheng Liu 2 3 , Kailiang Ren 2 3 , Qing Wang 1 3 , Qiming Zhang 2 1 3 , Cheng Huang 4 , Howard Katz 4 Show Abstract
1 Department of Materials Science and Engineering, Penn State University, University Park, Pennsylvania, United States, 3 Materials Research Institute, Penn State University, University Park, Pennsylvania, United States, 2 Department of Electrical Engineering, Penn State University, University Park, Pennsylvania, United States, 4 Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States
9:00 PM - C3.4
Dielectric Breakdown Properties of Organic-Inorganic Polymer Nanocomposites.
Lei Zhu 1 2 , Li Cui 1 2 , Amanda Feldman 1 , Gobinda Saha 1 3 , Alexandru Asandei 1 3 , Chunchuan Xu 1 , Steven Boggs 1 Show Abstract
1 Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States, 2 Department of Chemical, Materials, and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States, 3 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States
Silica nanoparticles in the range of 10~20 nm have been synthesized using the Stober method. In order to introduce compatibility of these silica nanoparticles with polymers, two methods are used; simple silane treatment and surface-initiated free-radical polymerization. In the first method, dodecyltriethoxysilane was used to coat the silica nanoparticles. In the second method, nitroxide-mediated radical polymerization (NMRP) of methyl methacrylate was carried out. The advantage of NMRP over other surface-initiated radical polymerization methods lies in that this reaction is free of metal ions, which are detrimental to the dielectric breakdown property of polymer dielectrics. Using both methods, the silica nanoparticle dispersion in polymer films was characterized by TEM. Uniform nanoparticle distribution was observed. The dielectric properties of these nanocomposite films, including dielectric constant, dielectric loss, and breakdown strengths as functions of frequency and temperature, were systematically studied. Especially, Weibull analyses of the breakdown properties for 1, 3, 5, and 10 wt % silica nanoparticle-filled poly(vinylidene fluoride-co-hexafluoropropane) [P(VDF-co-HFP)] films will be presented.
9:00 PM - C3.5
Melt Crystallization of Nanocomposites of Poly(Vinylidene Fluoride) with OMS.
Bedriye Gunduz 1 , Peggy Cebe 1 , Debeshu Amare 2 , Robert Alpern 4 , Jennifer Crawford 1 , Breanna Dolan 3 , Stacey Jones 2 , Ryan Kobylarz 2 , Matthew Reveley 1 Show Abstract
1 Physics, Tufts University, Medford, Massachusetts, United States, 2 Chemistry, Gallaudet University, Washington, District of Columbia, United States, 4 Mechanical Eng., Rochester Institute of Technology, Rochester, New York, United States, 3 Biotechnology, Rochester Institute of Technology, Rochester, New York, United States
Crystalline poly(vinylidene fluoride) shows piezoelectric properties in its oriented polar beta phase. The polar beta phase is usually obtained by drawing non-polar alpha phase PVDF films. Addition of organically modified silicates (OMS) to the PVDF results in beta crystal phase directly. In our previous work we investigated the impact of cold-crystallization on the structure of nanocomposites of PVDF with Lucentite STNTM OMS and observed the crossover composition in which the beta phase dominated. Here, melt crystallization of PVDF/OMS nanocomposites was studied in the range of 0 to 1.0 wt. % of OMS. Nanocomposite samples were crystallized from the melt at 150°C for one hour. Static and real-time wide and small angle X-ray scattering (WAXS, SAXS) and Fourier Transform infrared spectroscopy (FTir) were used to characterize the structure. Morphology information was obtained using polarizing optical microscopy (POM), and thermal properties were studied using differential scanning calorimetry (DSC). In crystallization from melt, a decrease in crystallinity index occurs as a result of an increase in OMS. While beta phase fraction increased with an increase of OMS content in the range of interest, the amount of alpha crystals was found to be dominant even at high OMS compositions. At 1.0 wt. % of OMS, beta crystals had reached at most 30% of the total crystallinity. POM studies showed smaller, less birefringent spherulites with higher melting temperature compared to alpha spherulites appeared with OMS addition. Growth rate of these weakly birefringent spherulites is smaller than that of the strongly birefringent alpha spherulites. Their amount and size increased with an increase of OMS, suggesting these spherulites may be beta phase.
9:00 PM - C3.6
Dielectric Properties of PVDF-based Polymer/ZrO2 Nanocomposites
Baojin Chu 1 , Bret Neese 1 , Xin Zhou 2 1 , Minren Lin 1 , Qiming Zhang 2 1 Show Abstract
1 Materials Research Institute, The Penn State University, University Park, Pennsylvania, United States, 2 Electrical Engineering Department, The Penn State University, University Park, Pennsylvania, United States
Nanocomposites, which are characteristic of much smaller particle size of the additives and much larger amount of interfaces between the additives and matrix, compared with conventional composite materials with micro-size additives, are very attractive for the applications of high-energy-density storage and high-pulse-power discharging capacitors. It has been reported that the addition of nanoparticles to a polymer matrix in a properly designed and fabricated nanocomposite can improve the breakdown field. However, it is less studied on making use of the unique opportunity in nanocomposites, i.e., very large surface area/volume ration, to significantly improve the dielectric and energy density as well as other properties of nanocomposites. Here we investigate nanocomposites based on relaxor ferroelectric PVDF terpolymer and a PVDF copolymer, both of which show very high energy density. We show that the presence of nanoparticles of ZrO2 in the terpolymer matrix improves the high field properties of the nanocomposites quite markedly. Specifically, even with very low volume content of nanofillers, the energy density of the nanocomposites can be raised markedly. The results on microstructure characterization and molecular conformations of the polymer matrix will also be discussed.
9:00 PM - C3.7
Influence of Particle Size and Thickness of Material on Anti-voltage Strength of Energy-storage Composite.
Dabing Luo 1 , Yan Guo 1 , Hanxing Liu 1 Show Abstract
1 State Key Laboratory of Advanced Technology for Materials’ Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei, China
9:00 PM - C3.8
Cyclolinear Polycarbosilane Graft Copolymers as Potential Low Dielectric Materials.
Jaeyong Hyun 1 , Junwon Han 1 , Chang Ryu 1 , Leonard Interrante 1 Show Abstract
1 Chemistry, Rensselare polytechnic institute, Troy, New York, United States
9:00 PM - C3.9
Effect of Molecular Structure of Scavengers on Copper Diffusion Deterrence in Low k Film.
Yutaka Nomura 1 , Daisuke Ryuzaki 2 , Mitsumasa Koyanagi 3 Show Abstract
1 , Hitachi Chemical Co., Ltd., Hitachi-shi, Ibaraki, Japan, 2 , Hitachi, Ltd., Kokubunji-shi, Tokyo, Japan, 3 , Tohoku University, Sendai-shi, Miyagi, Japan
The wiring size of ultra-large-scale integrated circuits also decreases with the miniaturization of the design rule. When the barrier metal is not thin, the wiring trench will be occupied by the barrier metal having higher resistance than copper. As a result, the effective resistance of wiring will rise and the advantage of copper wiring will not be able to actualize. Low dielectric constant (low k) material with high deterrence ability of copper diffusion was then proposed to reduce the effective resistance of copper wiring. Specifically, a chemical agent that chemically combines with copper (copper scavenger) was added to the organic low k material. A copper scavenger was selected from the non-ionic compounds that do not raise the dielectric constant of the low k material. Specifically, triazole derivatives were employed as scavenger since they are known as copper anticorrosive. First, we confirmed the validity of this concept, using benzotriazole (BTA) as the copper scavenger. Copper diffusion deterrence ability of the materials was mainly evaluated from time dependent dielectric breakdown (TDDB). The dielectric breakdown life of the organic low k material with BTA was about two orders of a magnitude higher than that of BTA-free organic low k material, at electric field intensity of 0.1MV/cm.Next, the dominant factor of copper diffusion deterrence ability for the organic low k materials with copper scavenger was investigated, using copper scavengers with different scavenge ability or molecule size. The dielectric breakdown life of these materials was clearly dependent on the scavenge ability of the copper scavenger. Moreover, in the examination range, it was proved that the molecule size of the copper scavenger did not contribute to the copper diffusion deterrence ability.
Vivek Bharti 3M Company
Zhongyang Cheng Auburn University
Qiming M. Zhang The Pennsylvania State University
Yoseph Bar-Cohen Jet Propulsion Laboratory
Gerhard M. Sessler Darmstadt University of Technology
C4: High-K and Low-K Materials
Tuesday AM, November 28, 2006
Room 201 (Hynes)
9:30 AM - **C4.1
Ferroelectric Polymers with Chemically Tunable Dielectric Constants.
YingYing Lu 1 , Jason Claude 1 , Qiming Zhang 1 , Qing Wang 1 Show Abstract
1 Dept. of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States
High dielectric constant polymers are becoming crucial components in advanced electronic devices such as memory and gate dielectrics for integrated circuits, and stationary power generation and miniature capacitors for telecommunication. We present a modular approach toward poly(vinylidene fluoride) based ferroelectric polymers with high dielectric constants and energy densities. This strategy is based on a two-step reaction including the co-polymerization of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) and a subsequent hydrogenation reaction. Due to the similar reactivity of VDF and CTFE in free radical polymerization and quantitative yield of dechlorination reaction, the chemical compositions of the resulting terpolymers can be precisely controlled, leading to tunable Curie temperatures and dielectric constants. A library of the ferroelectric polymers with dielectric constants varying from 11 to 50 measured at 1 kHz and room temperature has been prepared. The structural characteristics including microstructure, chain conformation, and crystallinity of the polymers have been carefully elucidated as a function of the chemical composition by 1H and 19F NMR, Fourier transform infrared spectroscopy, and wide angle X-ray diffraction. The influence of the polymer compositions on thermal transitions and dielectric constants has also been investigated.
10:15 AM - C4.3
Novel Fluorinated Low-Dielectric Constant Photodefinable Polymers for Low-Temperature Polymer Processing
Michael Romeo 1 , Kazuhiro Yamanaka 1 2 , Kazuhiko Maeda 2 , Clifford Henderson 1 Show Abstract
1 School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 , Central Glass Co., Ltd., Tokyo Japan
Polyimides have been widely used in a variety of microelectronics applications due to their excellent thermal stability, chemical resistance, and good dielectric performance. For example, polyimides are widely used as films for protection and insulation layers for ULSI and multi-chip modules. Photosensitive polyimides in particular have received significant attention due to the reduction in processing complexity and cost required to produce patterned layers as compared to their non-photo-definable analogs. There are generally two approaches to producing photosensitive polyimide compositions: (1) formulations based on the use of poly(amic-acid) precursors which are coated, imaged, and then thermally converted to their imide form and (2) polyimides functionalized with hydrophilic groups (e.g. phenol). There are several disadvantages to using formulations based on poly(amic-acid) precursors including the high curing temperatures required to convert the polymer to the imide form, the build-up of film stress during such high temperature curing, and difficulty with swelling and control of the dissolution rate of such materials during development. However, the use of pre-imidized polyimides which are made solution processable and compatible with aqueous alkaline developers by addition of hydrophilic, ionizable groups to the polymer such as phenol is also problematic since the presence of such groups in the polymer generally degrades the dielectric constant and water uptake performance of the material. The goal in this work is to overcome these problems by developing new low dielectric constant polyimides that can be formulated into photo-definable materials and processed at low temperatures.In this work the use of a novel hexafluoroisopropanol (HFA)-substituted diamine to synthesize novel poly(amic-acid), polyimide, and related polymers is reported. The resulting polymers exhibit good solubility in a variety of solvents (e.g. acetone, methanol, THF, PGMEA) and 0.26 N TMAH aqueous developers. Photosentitive polymer compositions based on formulation of the HFA-substituted polymers with a DNQ inhibitor were found to produce high resolution patterns with good sensitivities (<200 mJ/cm2) and reasonable contrasts using I-line lithography. The HFA groups in the polymer are contained on a substituent group attached to the main chain by an ester linkage. This HFA substituted functional group can be easily removed from the polymer after exposure and development of the patterned image by thermal treatment of the polymer at temperatures above approximately 250 oC. This removal of HFA groups produces a polymer which does not swell in its casting solvents, is insoluble in aqueous alkaline developers, and which possesses a substantially lower dielectric constant than the original polymer. This paper will provide complete synthetic details and a discussion of the polymer physiochemical properties.
10:30 AM - C4.4
``Green" Processing for Creating Low-k Metalizable Polymer Films using Supercritical Carbon Dioxide.
Tadanori Koga 1 , John Jerome 1 , Chelsea Gordon 2 , Maya Endoh 1 , Miriam Rafailovich 1 Show Abstract
1 , Stony Brook University, Stony Brook, New York, United States, 2 , Half Hollow Hills High School, Dix Hills, New York, United States
11:30 AM - C4.6
Diagnostic of the Self-healing Effect in P(VDF-TrFE-CFE) Terpolymer Coated with PEDOT Conducting Polymer Electrode.
Kailiang Ren 1 2 , Sheng Liu 1 2 , Minren Lin 2 , Qiming Zhang 1 2 Show Abstract
1 Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania, United States, 2 Material Research Institute, Pennsylvania State University, University Park, Pennsylvania, United States
Recently P(VDF-TrFE-CFE) polymer attracts a great deal of attention due to the high energy density, giant strain response, etc. For these applications, the electric breakdown in the high electrical field is an issue which is needed to be addressed. For many polymeric materials, self-healing or graceful failure is often observed at electric breakdown. This paper investigates the self-healing effect in P(VDF-TrFE-CFE) terpolymer films coated with PEDOT conducing polymer and comparison is made with terpolymer films using metal electrodes. It was observed that the conductive polymer coated terpolymer films show self-healing after breakdown. That is, after the electric breakdown, the capacitance of the films decreases slightly and the dielectric loss decreases greatly, indicating elimination of “weak” spots in the films. These films after breakdown can still be used for high field operation. The aim of the study is to understand the mechanism of the self-healing in P(VDF-TrFE-CFE) terpolymer coated with conductive polymer electrodes. Both of the conduction current and the charge are been investigated in the self-healing process. This work was supported by NIH.
11:45 AM - C4.7
Polymeric Electret Nanostructures and Biomaterials for Advanced Electronics and Biomedicine
Cheng Huang 1 , James West 2 , Shawn Lim 3 , Howard Katz 1 Show Abstract
1 Materials Science and Engineering Department, Johns Hopkins University, Baltimore, Maryland, United States, 2 Electrical and Computer Engineering Department, Johns Hopkins University, Baltimore, Maryland, United States, 3 Biomedical Engineering Department, Johns Hopkins University, Baltimore, Maryland, United States
The development of new polymeric electret materials and electrical capacitor-derived devices with built-in functionality has generated considerable interest for advanced electronics and biomedicine. Especially, real charge or polarization charge storage has been in many biopolymers and biomaterials, which implies that these materials can behave as electrets capable of performing certain functions for biomedical applications as well as fundamental studies of biophysical phenomena. The basic effects of electrets including space-charge electrets and dipolar electrets are based primarily on electrostatic induction. Recently, by exploiting the electrostatic polarization of electrets and interface coupling between organic semiconductors and gate electrets, organic field-effect transistors, inverters, and logic circuits have been developed on gate electrets, and polymer electret microphones and sensors have been built/integrated on air-gap organic thin-film transistors and circuits. However, it is still challenging to control and manipulate charge in space-charge electrets and to develop high-performance dipolar electrets. This talk will describe a nano- and meso-measurement method to detect and control charge dynamics in space-charge electrets and nano-interface controlled electronic (NICE) devices. Control of charge trapping, transport and organic semiconductor-electret interface structures not only improves the performance of organic field-effect transistors but also realizes the (majority carrier sign) inversion operation of organic semiconductor thin-film transistors and complementary inverters as building blocks for single-component organic electronics. In addition, by exploiting biomimetics and molecular self-assembly, “inner-spring mattress” polymeric nanostructures and a class of biomimetic polymeric materials of dipolar electrets have been developed. Orientation-on-demand biopolymeric films with 1-2 connectivity can exhibit high thermomechanical stability, dielectric, mechanical and electromechanical responses compared to 1-3 ceramic/polymer composites due to high molecular orientation, coupling, and dielectric anisotropy of polymer networks and helical molecular coil springs self-assembled inside the ellipsoidal voids.
12:00 PM - C4.8
Dielectric Properties of CuPc Based Composites: A First Principles Computational Study.
Ning Shi 1 , Rampi Ramprasad 1 Show Abstract
1 Institue of Materials Science, Department of Chemical, Materials and Biomolecular engineering, University of Connecticut, Storrs, Connecticut, United States
12:15 PM - C4.9
Parylene C used as Insulating Hydrophobic Layerfor Liquid Lenses based on Electrowetting.
Julien Legrand 1 , Mathieu Maillard 1 , Jérôme Peseux 1 , Gaetan Liogier 1 , Franck Amiot 1 , Jean-Christophe Robert 1 , Bruno Berge 1 Show Abstract
1 , VARIOPTIC, Lyon France
12:30 PM - C4.10
Study of High-K Dielectric Layers on Porphyrin Polymers for Multi-state Charge Storage.
Srivardhan Gowda 1 , Guru Mathur 1 , Zhong Chen 1 , Veena Misra 1 Show Abstract
1 Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina, United States
Hybrid silicon/molecular devices incorporating redox-active porphyrin monolayers have been shown to have discrete energy states, which makes them attractive for use in multi-state, low-voltage memory devices. Recently, we have shown that porphyrin polymer layers retains the advantages of individual molecules, such as discrete energy states, low-voltage operation etc., and also provides for significantly higher charge density (100 X) as compared to a porphyrin monolayer. However, to make high density solid state devices, it is imperative to replace the electrolyte gate, which forms an extremely thin insulating double layer (~10 nm) at the electrolyte-molecule interface, with a combination of metal gate and an ultra-thin high-k dielectric layer. Previous attempts to deposit solid-state layers on monolayers have led to loss of redox-activity in the molecules. In this study, it is shown that the redox properties of the molecules in porphyrin polymer on silicon and titanium nitride (TiN) surfaces are preserved after the deposition of subsequent high-K dielectrics. The high-K dielectric layers used were Aluminum Nitride (AlN), deposited by reactive sputtering of Al in N2, and Hafnium Oxide (HfO2), formed via atomic layer deposition (ALD). Dry voltammetry (CyV) of these structures showed only parallel-plate capacitor charging without any distinct redox behavior. However, the same structures measured with an electrolyte probe revealed peaks in current corresponding to charging and discharging of two redox states of the porphyrin molecule. This indicates that the porphyrin polymer survived the deposition of solid-state capping layers thereby retaining the redox properties. The absence of redox-related peaks in dry cell measurement can be attributed to one of the two reasons – (i) CyV measurement is much slower compared to redox kinetics in dry cell and hence cannot capture the transients associated with charging and discharging of molecules, or (ii) it is necessary for the screening charges to be in close proximity of the molecules in the polymer film for oxidation (molecule losing an electron) and electron-hopping in the polymer film and this may be provided for in case of electrolyte gate where in the counter-ions can possibly migrate/diffuse into the matrix of the polymer film. It was also found in electrolyte probe measurements of capped porphyrins that as the thickness of the high-K layer increased the measured redox-charge density decreased, and the redox-kinetics became slower. In addition, the endurance of the porphyrin layers capped with high-K dielectric improved. In summary, the multi-state charge-storage property of redox-active porphyrin polymer is modified in presence of ultra-thin high-K layers and this route can be potentially utilized to realize solid-state silicon/molecular memory devices.
12:45 PM - C4.11
Synthesis and Dielectric Characterization of Poly Chloro-para-xylene Thin Films.
Pratyush Tewari 1 , Michael Lanagan 1 Show Abstract
1 Department of Engineering Science and Mechanics, Pennsyalvania State University, University, University Park, Pennsylvania, United States
C5: Dielectric Composites
Tuesday PM, November 28, 2006
Room 201 (Hynes)
2:30 PM - **C5.1
Microstructure-Based Simulation of the Dielectric Properties of Polymer-Ceramic Composites for Capacitor Applications.
Jeffrey Calame 1 Show Abstract
1 Electronics Science and Technology Division, Naval Research Laboratory, Washington, District of Columbia, United States
Composite materials are a candidate for improved capacitor dielectrics. For instance, polymer-ceramic composites may represent a way to obtain some of the best characteristics of dissimilar materials in one physical system, namely the high dielectric constant of ferroelectric ceramics and the high dielectric strength, self-healing ability, and fabrication diversity of polymer dielectrics. A critical research issue is the prediction of the dielectric properties of composites using computer simulations. Such a capability would allow experimental synthesis to be focused on the most promising microstructural approaches, without the need to physically test each idea. It would also be critical for understanding tradeoffs between competing requirements. The modeling consists of two important and intermingled tasks, which are (1) the “virtual reality” creation of three-dimensional model spaces representative of real material microstructures and models of how they change during material processing, and (2) the prediction of the composite dielectric permittivity and electric field distributions with finite-difference-based quasi-static or electromagnetic field solvers. A number of polymer-ceramic composites, including barium titanium oxide (BTO) particles in a PVDF matrix, as well as BTO particles in a relaxor ferroelectric terpolymer matrix, have been simulated with this methodology. The results of systematic studies of how the permittivity varies as a function of the particle clustering morphology and the filling fraction will be described, along with studies of electric field statistics within the polymer matrix. The investigations include models for the onset, evolution, and impact of undesired porosity at high filling fractions. Finally, research on including realistic rough ceramic surfaces into multi-scale dielectric models of particulate and layered polymer-ceramic composites will be presented.
3:00 PM - **C5.2
High-dielectric Constant Polymer Composites.
Ce-Wen Nan 1 Show Abstract
1 Materials Science & Engineering, Tsinghua University, Beijing China
3:30 PM - C5.3
A Study of the Microwave Dielectric Behavior and Microstucture of Electrically Lossy Al2O3-Precursor-Derived-SiC Composites.
Jacob Battat 1 , Jeffrey Calame 1 Show Abstract
1 , Naval Research Laboratory, Washington , District of Columbia, United States
Electrically lossy, microwave-absorbing, ceramic-based composites were produced by infusion of a one-step liquid polymer precursor to SiC into porous alumina discs, and subsequent heat treatments. Porous composites composed of Al203 and amorphous SiC were synthesized using repeated steps of polymer infusion and pyrolysis in an argon ambient at 1000C. Further heating at 1600C after each pyrolysis treatment was employed to create a second set of composite samples of reduced porosity consisting of nanocrystalline Beta-SiC. Analysis of complex dielectric permittivity in the microwave frequency range reveals that for Al2O3-SiC composites produced at 1600C, high, controllable losses are attainable, as well as an inverse power law relation of e' with f over a broad frequency range, while as-pyrolyzed composites exhibit more moderate e' values. Hierarcical vesicular morphology of amorphous SiC in the as-pyrolyzed composites is linked to non-Debye dielectric behavior, with networks of conductive SiC leading to enhanced percolation and increased DC conductivity. By contrast, in composites formed at 1600C, pathways for more localized conductivity are formed by networks of adjacent cubic SiC crystallites with alternate twinning boundaries. At higher frequency values, the as-pyrolyzed composites tend to exhibit universal dielectric response behavior, linked to the disordered structure of pyrolyzed SiC, while the relationship of conductivity with frequency in 1600C-treated composites is marked by a superlinear power law. In both cases, samples derived from a large number of infusion and heat treatment repetitions exhibit non-Debye behavior and low-frequency dielectric relaxations. Furthermore, the ability to control complex dielectric permittivity by adjusting SiC composition is attainable in both as-pyrolyzed and 1600C-treated composites.
3:45 PM - C5.4
Fabrication of Energy Storage Media BST/PVDF-PAn
Dabing Luo 1 , Yan Guo 1 , Hanxing Liu 1 Show Abstract
1 State Key Laboratory of Advanced Technology for Materials’ Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei, China
Permittivity and electric strength were the most important parameter for energy storage material. Higher permittivity and electric strength, higher energy storage density. Furthermore, the material should also be easy to machine. Composite could take all these features. Among the researches so far, the permittivity and electric strength were hard to enhance, especially the electric strength since there existed inner induced field due to the permittivity difference between ceramics and polymers. In this research, the electric field distributions were simulated. The figures recommend that the inner field was heavier as the difference of permittivity between particles and continuous media were stronger. According to the analyses, the permittivity gap should be diminished in order to optimize the inner field in composites. Ordinarily, ceramics prompted higher dielectric constant, while the polymer did the opposite. The polymers usually took on poor permittivity due to their low polarization in the poly-chains. The polymers with highest polarization, PVDF, its relative dielectric constant is no more than 14. Hence, additive should be employed in order to enhance the permittivity of continuous media. Poly-aniline was a kind of polymer which the electric properties could be adjusted according to the fabrication routine. It could be conductor, semi-conductor or insulator. Furthermore, the molecule structure was similar to PVDF, making them connect well. Thus, the permittivity could be controlled. In this research, PAn was resolved in PVDF by employing emulsion polymerization method. Both the XRD and SEM pattern illustrate that the PAn was resolved by PVDF, rather than those media mixed the PAn and PVDF directly. The polymers were saturated in muriatic acid with different concentrate and their permittivity and electric strength were determined. The permittivity of polymer was raising as long as the pH of liquid went below, and the electric strength went otherwise, as most dielectric media. BST was employed as ceramic component. It was a kind ceramic with medium dielectric constant and the permittivity could be optimized while modifying the portion of Barium and Strontium. The permittivity of both components could be handled, making the couple of dielectric constant match well. Composing them as energy storage media, the properties of composites were measured. When pH of muriatic acid decreased, the dielectric constant of polymers raised, and the electric strength of composite enhanced. When pH=1, the mass concentrate of PAn was 25% in polymer, and the relative permittivity of BST was 700, the anti-voltage strength of composite was 26.22kV/mm, and the relative permittivity was 301. The energy storage density was 0.9185j/cc.
4:30 PM - C5.5
Double-percolating Ferrite-Ni-polymer Composites with Enhanced Permittivity and Permeability.
Yang Shen 1 , Bao-Wen Li 1 , Ce-Wen Nan 1 Show Abstract
1 materials science and engineering, Tsinghua University, Beijing, Beijing, China
4:45 PM - C5.6
Hydrophobic Dielectrics of Fluoropolymer / BaTiO3 Nanocomposites for Low-Voltage and Charge-Storing Electrowetting Devices.
Murali Kilaru 1 , Gui Lin 1 , James Mark 1 , Jason Heikenfeld 1 Show Abstract
1 , Univ. of Cincinnati, Cincinnati, Ohio, United States
5:00 PM - C5.7
Dielectric Properties of CaCu3Ti4O12–P(VDF-TrFE) Composite
Xiaobing Shan 1 , Xin Yang 1 , Kewei Zhang 1 , Zhongyang Cheng 1 Show Abstract
1 Materials Research and Education Center, Auburn University, Auburn, Alabama, United States
By using conventional solution casting method, a flexible ceramic [CaCu3Ti4O12 (CCTO)]-Polymer [P(VDF-TrFE)] has been fabricated. The CCTO ceramic powders with a relative uniform size were prepared using traditional powder processing method. The dielectric properties of these films with different CCTO fractions were determined. The process was optimized to achieve high dielectric constant. A dielectric constant about 120 was obtained at room temperature. The dielectric relaxation process obtained in the samples was analyzed using Cole-Cole equation.
5:15 PM - C5.8
Observation of High-density Charge Storage in Hybrid Silicon/Molecular Electronic Devices with Organic Polymers.
Srivardhan Gowda 1 , Zhong Chen 1 , Guru Mathur 1 , Veena Misra 1 Show Abstract
1 Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina, United States
To obtain high charge storage devices, solid-state hybrid silicon/polymer devices were fabricated by depositing ultra thin dielectric layers (AlN or Al2O3) on polymers of (i) redox-active (porphyrin) or (ii) non-redox (biphenyl) molecules incorporated on silicon followed by deposition of Al metal gate using resistance-heated evaporator. Recently, porphyrin polymers have been shown to have high density (1x1015 /cm2) redox charge states, which are quantized with applied voltage and accessible at relatively low voltages. In this work, the effort was to create high density charge storage devices by intentionally generating high interface trap density (Dit) and charge centers in the bulk of not only redox but also non-redox polymer to investigate the impact that redox states have on bulk trapping of polymer films. The interface traps and bulk charge centers manifested as peaks and hysteresis, respectively, in the Capacitance-Voltage (CV) characteristics of these devices. The simulated CV characteristics of the capacitors indicated that peaks in CV are observed only if the Dit were greater than 5x1013 /cm2. The width of the peaks increased with increasing thickness of the dielectric layer on top of the polymer film similar to that in simulated CV. The peaks in the simulated CV disappeared when the states were moved away from the silicon interface and this was observed in the experiments as well when the polymer film was on top of a thin SiO2. The magnitude of the hysteresis varied between 0.5-2.0 V depending on the the thickness of the dielectric layer. The effect of polymer film thickness on the peaks and hysteresis in CV characteristics were also studied. Capacitance-voltage characteristics of control capacitors without any organic polymer did not exhibit any hysteresis indicating that the charge centers were located in the bulk of the polymer film. The location and origin of these charges and their relationship to the bonding within the polymer will be discussed. From these findings, it is proposed that organic polymers can be incorporated into silicon capacitors to achieve very high-density charge storage devices.
5:30 PM - C5.9
Dielectric Relaxation Studies of Nanoscopically Confined PEO/Li+ Complexes.
Georgios Polizos 1 , Andreas Schönhals 2 , Evangelos Manias 1 Show Abstract
1 Materials Science & Engineering, Penn State University, University Park, Pennsylvania, United States, 2 , Federal Institute of Materials Research and Testing, Berlin Germany
5:45 PM - C5.10
Assembly of Oxidic Nanoparticles and Polymethylmethacrylate Beads.
Simone Herth 1 2 Show Abstract
1 Faculty of Physics, University Bielefeld, Bielefeld Germany, 2 Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York, United States
For nanocomposite materials, their electrical properties could be improved by placing the nanoparticles equidistant to one another or by decreasing the width of the interparticle distance distribution. One attempt to achieve this special arrangement is the assembly of nanoparticles into the interstitial sites of an ordered lattice of uniform polymer beads, such as polymethylmethacrylate (PMMA), by centrifugation. Due to the different densities of PMMA and oxidic nanoparticles, the PMMA would normally always settle down on top of the nanoparticles during the centrifugation process. For that reason, the nanoparticles were linked with the PMMA beads by a silane linker prior to centrifugation. At higher concentrations, the nanoparticles form a continuous coverage on the beads. On the other hand, slowly drying a droplet of a dispersion of PMMA beads and SiO2 nanoparticles filled the empty space between the beads with nanoparticles. Scanning electron micrographs of the dried pellets revealed a similar distance between the nanoparticles, a short range order of the PMMA beads, a good dispersion of nanoparticles, and a good adhesion of the nanoparticles to the PMMA beads.
Vivek Bharti 3M Company
Zhongyang Cheng Auburn University
Qiming M. Zhang The Pennsylvania State University
Yoseph Bar-Cohen Jet Propulsion Laboratory
Gerhard M. Sessler Darmstadt University of Technology
Wednesday AM, November 29, 2006
Room 201 (Hynes)
9:30 AM - **C6.1
ERPs Based Wearable Haptic Systems.
Danilo DeRossi 1 Show Abstract
1 Interdepartmental Research, University of Pisa, Pisa Italy
Artificial sensory motor systems granting the power to reach out and interact with illusory objects and granting the objects the power to resist movement or to manifest their presence are now under development in a truly wearable form using an innovative technology based on electro-responsive polymers. The integration of electroresponsive polymeric materials into wearable garments endows them with strain sensing and mechanical actuation properties. The methodology underlying the design of haptic garments has necessarily to rely on knowledge of biological perceptual processes which is, however, scattered and fragmented. Nonetheless, use of new polymeric electroresponsive materials in the form of fibres and fabrics, combined with emerging biomimetic concepts in sensor data analysis, pseudomuscular actuator control and biomechanic design, may not only provide new avenues toward the realization of truly wearable kinaesthetic and haptic interfaces, but also clues and instruments to better comprehend human manipulative and gestural functions. In this talk, the biological bases which characterize sensory-motor functions in humans are briefly summarized, focusing on their perceptual and motor control features. Electro-responsive polymer actuators, which we are currently investigating, are then discussed with emphasis given to their unique capabilities in the phenomenological mimicking of skeletal muscle actuation. Finally, the conception, early stage implementation and preliminary testing of a fabric-based wearable interface endowed with spatially redundant strain sensing and distributed actuation are illustrated with reference to a wearable upper limb artificial kinaesthesia system.
10:00 AM - **C6.2
Pyroelectric Detection of Ferroelectric Heating in a VDF/TrFE Copolymer Film.
Takeo Furukawa 1 , Yuuji Ikezaki 1 , Takashi Nakajima 1 , Yoshiyuki Takahashi 1 Show Abstract
1 Faculty of Science, Tokyo University of Science, Tokyo Japan
10:30 AM - C6.3
Fabrication and Use of Electroactive Polymer Ribbon Actuators.
Tim Fofonoff 1 , Ian Hunter 1 Show Abstract
1 BioInstrumentation Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Electroactive polymer actuators, such as those based on polypyrrole, offer muscle-like properties that could be useful in the creation of biomimetic devices. Some actuator applications call for macroscale forces and displacements not typical of electroactive polymer actuators made to date. In order to scale these properties, new processing techniques have been developed. We report the fabrication of hexafluorophosphate doped polypyrrole actuators in continuous ribbon form with lengths exceeding 5 m. Widths and thicknesses were arbitrarily chosen on the order of 5 mm and 20 µm, respectively. Computer numerically controlled processes were utilized in order to achieve a highly uniform result, and gold was optionally incorporated into the ribbons in order to increase performance. As the size of these actuators is increased, several significant issues become more pronounced and must be considered. These include potential iR drops along the ribbon actuators, nonlinear effects such as rippling across the tensioned ribbons, and the reduced strain rates common with thicker films. The ability to tension and adjust the polymer in response to swelling and creep also plays a larger role at the macroscale. This paper addresses these issues and demonstrates solutions to these problems by describing devices fabricated to incorporate these ribbon polymer actuators.
10:45 AM - C6.4
Design and Characterization of Electroactive Polymer Based Composites for Mechanosensors.
Jin Wang 1 , Chunye Xu 2 , Minoru Taya 2 1 , Yasuo Kuga 3 Show Abstract
1 Materials Science and Engineering, University of Washington, Seattle, Washington, United States, 2 Mechanical Engineering, University of Washington, Seattle, Washington, United States, 3 Electrical Engineering, University of Washington, Seattle, Washington, United States
11:30 AM - C6.5
Spray Cast Silicone and Polyurethane Dielectric Actuators.
Jeffrey Szabo 1 , John Hiltz 1 , Jacob Leidner 2 , Jason Massey 2 Show Abstract
1 Emerging Materials Section, DRDC Atlantic, Halifax, Nova Scotia, Canada, 2 , Bodycote Materials Testing Canada, Mississauga, Ontario, Canada
The high electric fields required for dielectric actuator operation necessitate the use of thin elastomeric films in their fabrication. In this study, various methods were investigated to produce thin films of polyurethane and silicone for dielectric actuators. The study included the development of a crosslinked polyurethane formulation for the dielectric layer. Material characterization included infrared spectroscopy, dynamic mechanical analysis, and dielectric analysis. Drawdown was successfully employed to fabricate silicone, thermoplastic polyurethane, and thermosetting polyether polyurethane single layer actuators with relatively small areas (80 mm x 50 mm). Spray casting was also investigated as a method to fabricate relatively large area (2000 m x 75 mm ) films that were subsequently rolled into cylindrical actuators. A custom built apparatus for automating the production of large area multi-layer films was designed, constructed, and used to produce a total of 29 rolled actuators. The compliant electrodes were either brushed graphite, or electrically conductive elastomeric composite films applied by spraying in alternate layers with the dielectric polymer.
Electrical characterization of the actuators was carried out before and after rolling. The most difficult challenges encountered were related to electrical termination of the compliant electrodes, and dielectric film conductivity. It was not possible to terminate graphite based electrodes reliably, but a polyurethane based electrode formulation in combination with a silicone dielectric did result in consistent termination of the actuators. The thickness of the dielectric had the expected effect on capacitance, with capacitance being inversely proportional to the thickness. The capacitance of the rolled actuators was double that of lay-flat actuators. While some of the rolled actuators had the expected electrical properties, other actuators showed considerable conductivity across the dielectric layers. Actuators produced with thicker dielectric layers tended to be of higher resistance. Actuation strains up to 3% were measured along the cylinder axis using a non-contact laser technique.
11:45 AM - C6.6
Dynamic Behavior Investigation of the Piezoelectric PVDF for Flexible Finger Printing.
Wen Yang Chang 1 2 , Ying-Hui Cheng 1 , Chun-Hsun Chu 1 , Ying-Chiang Hu 1 Show Abstract
1 , Industrial Technology Research Institute, Tainan Taiwan, 2 Department of Engineering Science, National Cheng Kung University, Tainan Taiwan
12:00 PM - C6.7
Dielectric Polymer with High Electric Energy Density and Fast Discharge Speed
Xin Zhou 1 , Baojin Chu 2 3 , Kailiang Ren 1 , Bret Neese 2 3 , Minren Lin 3 , Qing Wang 2 3 , Qiming Zhang 1 2 3 Show Abstract
1 Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Materials Science and Engineering Department, The Pennsylvania State University, University Park, Pennsylvania, United States, 3 Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania, United States
Dielectric materials with high energy density, used to store charges and electric energies, play a key role in modern electronics and electric systems. Among them, dielectric polymers are a promising candidate for energy storage applications due to relatively high energy density and low cost, low dielectric loss etc. In this paper, we show that a). high electric displacement with high enough dielectric breakdown field b). small remnant polarization c). matched dielectric constants to avoid early polarization saturation are three key properties to achieve high energy density and efficiency. Based on these consideration, we demonstrate that a very high energy density(>17J/cm3 under 575MV/m) with low loss can be achieved in defect modified poly(vinylidene fluoride) polymers, by combining the non-polar to polar molecular structure changes in the polymer with proper dielectric constants to avoid the electric displacement saturation at electric fields much below the breakdown field. In addition, the data measured from the specially designed high speed capacitor discharge circuit show the defect modified poly(vinylidene fluoride) polymers also possess a very fast discharge speed(<1μs), another desirable characteristic for energy storage capacitor applications.
12:15 PM - C6.8
Actuation of Self Assembled, Porous Films of Poly(3-hexylthiophene).
Priam Pillai 1 , Patrick Anquetil 1 , Ian Hunter 1 Show Abstract
1 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Electroactive conducting polymers, such as polypyrrole, polyaniline, and polythiophenes are currently studied as novel biologically inspired actuators. The actuation mechanisms in these materials are based on the movement of ions in and out of the polymer film. Hence, actuation properties such as speed and displacement of the polymers can be diffusion limited. These properties may be enhanced by exposing more of the polymer surface to the ions. For example, decreasing the length ions have to travel within the actuator by a factor of two could lead to an improvement in strain rate by a factor of four. Poly (3-hexylthiophene) films doped with gold and iodine have shown limited actuation in ionic liquids and in acetonitrile. However, these properties may be improved by controlling the surface structure of the films. A unique surface templating technique using breath figures has been developed for poly (3-hexylthiophene) [L. Song et al, Adv Mater. 2004, 16, No 2, 115]. Spherical holes form on the surface of polymer films during the drop casting process if moist air is blown over the top of the film. This technique has been used to generate 4-10 μm holes on the surface of thin poly (3-hexylthiophene) films and may be used to influence the structure of thicker films as well. The hole sizes can be controlled by changing the velocity of the air blown over the surface. This direct control of the polymer morphology offers a unique opportunity to understand the influence of surface microstructure on actuation. Free standing sponge like films (5-20 μm in thickness) of poly(3-hexylthiophene) were generated using this technique and the influence of these holes on the actuation of poly (3-hexylthiophene) polymer films has been characterized.
12:30 PM - C6.9
Novel Highly Fluorinated Poly(Arylene Ether-1,3,4-Oxadiazole)s, Their Preparation and Sensory Properties to Fluoride Anion.
Jianfu Ding 1 , Michael Day 1 Show Abstract
1 Institute for Chemical Process and Environmental Technology, Natioanl Research Council Canada, Ottawa, Ontario, Canada
Highly fluorinated poly(arylene ether-1,3,4-oxadiazole)s (FPAEOx) have been prepared using an aromatic nucleophilic substitution reaction of 2,5-bis(pentafluorophenyl)-1,3,4-oxadiazole (FPOx) with hexafluorobisphenol-A (6F-BPA). The presence of the highly electron-withdrawing oxadiazole (Ox) group in FPOx significantly enhanced the reactivity of the para-fluorines such that the reaction could be completed in only 1 to 2 h at room temperature in the presence of 4.0 equivalent of potassium fluoride (KF). These mild reaction conditions with low reaction temperatures and the use of a mild base effectively prevented side reactions, and ensured the formation of polymers with a high molecular weight. FPOx itself and this unit in the FPAEOx were found to be capable of selectively binding fluoride anion (F-) with high affinity, and produced new peaks in UV and fluorescence spectra, which are in the regions well-isolated from the original peaks of FPOx or the polymer. The intensities of these resulting new peaks corresponded to the fluoride concentrations. All these features make the monomer and the polymer potential candidates for fluoride sensory and enable the detection a high reliability and a high sensitivity to the concentration as low as 0.1 ppm. This sensory system also showed a very high selectivity for detecting F-, displaying no response to other tested anions including Cl-, Br-, ClO4-, HSO4-, and PF6-.
12:45 PM - C6.10
Actuation Based on Π-stacking Intermolecular Interactions
Miklos Kertesz 1 , Gyoosoon Park 2 1 , Jingsong Huang 1 Show Abstract
1 Chemistry, Georgetown University, Washington, District of Columbia, United States, 2 Chemistry, Kookmin University, Seoul Korea (the Republic of)
Charged or neutral radicals often display π-stacking geometries that show signs of intermolecular covalent bonding based on the partial occupancy of π-orbitals. This interaction is sensitive to the number of π-electrons available for this bonding. We demonstrate these findings by analyzing known cases of intermolecular π-bonding in various radical dimers and chains and connect the intermolecular bonding properties to observed magnetic properties. The simulations involve molecular and periodic first principles density functional calculations. Various stacked chains are analyzed for their suitability as electrochemically driven actuating molecules.
C7: CNT and EAP
Wednesday PM, November 29, 2006
Room 201 (Hynes)
2:30 PM - **C7.1
Ionic Polymer Conductor Nano-Composites as Distributed Nanosensors, Nanoactuators and Artificial Muscles - A Review.
Mohsen Shahinpoor 1 Show Abstract
1 Environmental Robots, Inc., Biomedical Products Division, Albuquerque, New Mexico, United States
3:00 PM - **C7.2
Hybrid Organic Dielectrics for Flexible, Low Voltage Thin-Film Transistors and Charge Storage Applications.
Tobin Marks 1 Show Abstract
1 , Northwestern University, Evanston, Illinois, United States
Molecular materials scientists are skilled at designing and constructing individual molecules with the goal of imbuing them with predetermined chemical and physical properties. However, the subsequent task of rationally assembling them into organized, functional supramolecular architectures with precise, control of bulk electronic properties presents another level of challenge. In this lecture, synthetic and computational approaches to addressing such problems are described in which the ultimate goal is the fabrication of flexible electronic circuits and high-capacity charge storage devices employing unconventional materials classes and unconventional fabrication techniques. We discuss the design, synthesis, and characterization of new high-k nanoscopic gate dielectrics for thin-film transistors and hybrid dielectric structures for charge storage.
3:30 PM - C7.3
The Direct Correlation of Electrical and Mechanical Properties of Electrically Conducting Polymers by Conductive-Nanoindentation.
Ryan Major 1 , David Vodnick 1 , Oden Warren 1 , Syed Asif 1 Show Abstract
1 , Hysitron Inc, Eden Prairie, Minnesota, United States
Conductive polymers have been utilized in applications spanning a broad range of technical disciplines. Macroscale analytical techniques are often used to correlate electromechanical properties with sample composition, cross-link density, swelling ratio, etc. However, these methods are not sensitive enough to detect subtle changes related to material deformation processes at the nanoscale. Depth-sensing nanoindentation is a technique that has been used extensively for characterizing materials at the sub-micro/nanoscale. A new instrument has been developed which allows for the quantitative, simultaneous acquisition of both force-displacement and conductivity measurements. The sensitivity of this instrument to electromechanical effects makes it an ideal tool for studying conductive polymers. In this study we examined polymers of different composition, cross-linking agents, and swelling ratio to see how these factors affect the electromechanical properties/characteristics upon mechanical deformation. Environmental effects such as temperature and humidity will also be discussed.
3:45 PM - C7.4
Conductive Polymer Driven Catheter.
Tina Shoa Hassani Lashidani 1 , Victor Yang 2 , John Madden 1 Show Abstract
1 AMPEL, Electrical & Computer Engineering, University of British Columbia, Vancouver, British Columbia, Canada, 2 , Sunnybrook Hospital, Toronto, Ontario, Canada
A model of an active medical catheter intended for maneuvering and imaging inside the vascular system is described and initial experimental results are presented.Polypyrrole actuators are employed to induce bending. These actuators typically exhibit strains of between 2 and 8 %. Strains are electrochemically induced by voltages changes of 1 to 5 V per electrode. The strains are associated with the insertion or removal of ions to or from the polymer as it is charged or discharged.Thin layers of polypyrrole were deposited on the outside surface of commercially available catheters. Fabrication is achieved by coating the catheter tip with polypyrrole, and dividing the coating into segments that run the length of the tip. Application of a voltage between opposing halves in an electrolyte leads to deflection of the catheter towards the contracting side.Preliminary tests were performed on the fabricated catheter, which was operated at 0.1 Hz in an aqueous solution of sodium hexafluorophosphate and achieved a bending radius of 43 mm, meeting the required specifications. The degree of bending was predicted by a beam bending model. Model inputs included the moduli of the polypyrrole and the catheter components, as well as device dimensions. The model was used to optimize the polypyrrole thickness and length in order to achieve the needed degree of bending.Fast actuation of the catheter for optical scanning has been tested and the required 1 mm tip displacement, needed for imaging, was achieved at 10 Hz using a 24 mm long polymer coated catheter. It is desirable to further increase the operating frequency to 30 Hz, a common image scan rate. (A separate, non-polymer driven scan mechanism is being employed for the fast orthogonal scan.) Our dynamic beam bending model suggests that rate is not limited by viscous drag or beam inertia, but rather by the rate of ion insertion into the polymer. Based on our recent measurements of the ionic conductivity and diffusion coefficient of ions in polypyrrole, we estimate that ion flux is predominantly in the outer several hundred nanometers of the polymer, with the thickness of this active region dropping as frequency is increased. As a result the degree of bending drops with increasing frequency. This can be remedied by using a longer active length of polymer. Our models suggest that by coating the catheter’s final 30 mm it should be possible to produce 1 mm displacements at 30 Hz. This increase in length decreases the resonant frequency, but should still allow the device to be operated at or below resonance, enabling 30 Hz operation to be achieved.Our work demonstrates that the static and dynamic needs of an active catheter can be met. The substantial challenges remaining include finding methods of encapsulation.
4:30 PM - C7.5
A Study on Formation of Needle-like Polyanilines.
Woo-Hyuk Jung 1 , Dong-Young Kim 2 , Young-Moo Kim 3 , Stephen McCarthy 1 Show Abstract
1 Plastics Engineering Department, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 2 Photo Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 3 Department of Industrial Chemistry, Hanyang University, Seoul Korea (the Republic of)
Needle-like polyanilines (PANi) were prepared at 15 oC by emulsion polymerization and their conductivities were obtained up to 3 S/cm according to the addition rate of ammonium peroxysulfate (APS) aqueous solutions prepared with 0.4 to 0.5 APS/aniline ratios and 4 to 5 M aniline concentrations. Needle-like complexes doped with p-toluenesulfonic acid (pTSA) were prepared with the oxidant solution added slowly, such as for 3 to 3.6 hours at high reaction temperatures to have needle-like anilinium complexes polymerized without their breaking. Filler shapes are one of the most important parameters influencing a percolation concentration of conductive fillers dispersed in a non-conductive matrix. Needle-like polyanilines are used as conductive fillers to show electromagnetic interference and radar absorption effects.
4:45 PM - C7.6
Polarization Induced Surface Chemical Kinetics of Kapton-H Polyimide.
Satish Mahna 1 , Pushkar Raj 1 , Balbhadra Kaushik 1 Show Abstract
1 Physics, National Institute of Technology, Kurukshetra, Haryana, India
5:00 PM - C7.7
Native Domain Orientation and Local, Reversible Polarisation Switching in Ferroelectric Polymer Nanotubes.
Markus Geuss 1 4 , Martin Steinhart 1 , Yun Luo 1 , Petra Goering 1 , Andreas Rhein 3 , Ralf Wehrsphon 3 , Thomas Thurn-Albrecht 2 , Klaus Rademann 4 , Ulrich Goesele 1 Show Abstract
1 , Max-Plank-Institute of Microstructure Physics, Halle (Saale) Germany, 4 Institute of Chemistry, Humboldt University, Berlin Germany, 3 Institute of Physics, University of Paderborn, Paderborn Germany, 2 Institute of Physics, Martin Luther University, Halle (Saale) Germany
The controlled, local and reversible adjustment of the physical propertiesin the walls of nanotubes on a 100-nm scale is still a challenge inmaterials science. Ferroelectric polymer nanotubes combine uniquepiezoelectric, pyroelectric and nonlinear optical properties with commonadvantages of lightweight polymeric materials having high chemical andmechanical stability and the intrinsic anisotropy of a tubular geometry.We report on the reversible switching of the polarization orientation inthe walls of poly(vinylidene-ran-trifluoroethylene) P(VDF-ran-TrFE)nanotubes on a 100-nm scale by means of a conducting cantilever probe. Weprepared the nanotubes by wetting ordered nanoporous alumina templateswith the molten polymer. Subsequently, we cooled the samples to roomtemperature at a rate of .7 K/min. DSC measurements on releasedP(VDF-ran-TrFE) nanotubes show a pronounced Curie transition. Thetwo-dimensional confinement imposed by the tubular geometry leads tooriented crystallization in the nanotube walls. X-ray diffraction andtwo-dimensional piezoresponse force microscopy (PFM) revealed the presenceof a distinct native polarization in the longitudinal directions that is in line with the crystalline texture. Lateral domainsizes up to 100 nm characterize the native domain structure.Electric field simulations confirmed that the inhomogeneous electric fieldof the conductive PFM probe, which we applied for polarization switching,is limited to the area directly underneath the tip-tube nanocontact.Because only the transversal and the radial field components parallel tothe tube axis are effective upon polarization switching, artificial domainconfigurations with well-defined anisotropy form. We switched areas havinga lateral size of the order of 100 nm, as well as tube segments having alength of some 100 nm. We demonstrated the reversibility of thepolarization switching by the measurement of several successive localpiezoelectric hysteresis loops.
5:15 PM - C7.8
Multi-Scale Modeling of Ferroelectric Polymers
Rajeev Ahluwalia 1 , Michael Sullivan 2 , Jianwei Zheng 2 , David Srolovitz 3 , Alfred Huan 1 , Ping Wu 2 , Takehisa Ishida 4 , Kanzo Okada 4 , Sunil Bhangale 4 Show Abstract
1 , Institute of Materials Research and Engineering, Singapore Singapore, 2 , Institute of High Performance Computing, Singapore Singapore, 3 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States, 4 , SONY ELECTRONICS (Singapore), Singapore Singapore
Ferroelectric polymers are unique materials that are of interest due to their combination of good inertness, flexibility, low density and ease of fabricating. While their polarization is substantially less than the ceramic perovskites, this class of materials is still useful for certain devices.In this work, we develop a multi-scale framework to study the polarization switching behavior in ferroelectric polymers. The aim of the present work is to develop a modeling frame work that uses data from simulations at different length scales and requires very little experimental input. The model is based on the Landau-Ginzburg Devonshire (LGD) theory with the polarization as the order parameter. The Time Dependent Ginzburg Landau model is used to describe the kinetics of polarization switching. We also incorporate the depolarization fields generated due the polarization charges at the crystalline-amorphous regions. To make the LGD model material specific, the phenomenological parameters are obtained from atomistic molecular dynamics (MD) simulations. For example, we used MD simulations to obtain the Tc from polarization vs. temperature scans. Other parameters in the LGD polynomial are obtained by fitting the Polarization vs temperature data as well as the dielectric constant data. The gradient parameters are estimated from the domain wall energy data coming from MD. The results are compared with experimental results on switching properties of PVDF-TrFe 75-25 copolymers.
5:30 PM - C7.9
Effect of DC Glow Discharge Treatment on Surface Resistivity of Thin Films of Polypropylene (PP) and Polystyrene (PS).
Rajesh Kumar 1 , Vineet Sharma 1 Show Abstract
1 Physics, Jaypee University Of Information Technology, Solan, H.P, India
5:45 PM - C7.10
Nano-Structural Control of Molecular-Pore Stacked (MPS) SiOCH Films Using Plasma Copolymerization Reaction.
Hironori Yamamoto 1 , Fuminori Ito 1 , Munehiro Tada 1 , Tsuneo Takeuchi 1 , Naoya Furutake 1 , Yoshihiro Hayashi 1 Show Abstract
1 , NEC Corporation, Sagamihara, Kanagawa, Japan
Nano-structure of porous SiOCH films was controlled by plasma copolymerization reaction using two types of precursors of 6-membered ring (ring-A) and 8-membered ring (ring-B) organo-silica molecular, applicable for ULSI interconnect dielectrics toward 32nm-node and beyond.The ring diameters for ring-A and -B monomers were estimated as 0.35 and 0.45 nm, respectively. These monomers were vaporized in a liquid injection-type vaporizer with He carrier gas and were introduced into a PECVD reactor. The chemical composition of the deposited film was evaluated by FTIR and Raman spectroscopic analysis. The film properties such as k-value, elastic modulus and pore size were measured by Hg-probe, nano-indenter, and small angle X-ray scattering, respectively. Here, effects of precursor molecular structures of the ring-type organo-siloxane for plasma co-polymerization reaction were investigated on the mechanical strength of SiOCH film deposited.The k-value of copolymerized SiOCH films from the mixture of ring-A and -B slightly increased with increasing the molar ratio of the ring-B to the ring-A monomer. In contrast, the elastic modulus dramatically improved by adding the ring-B to the ring-A monomer. Consequently, the copolymerized SiOCH films showed the high elastic modulus, keeping the low k-value. In order to reveal the hardening mechanism, the chemical structures of the films were systematically evaluated by Raman and FTIR. The SiOCH film derived from the ring-A consists of the 6-membered ring and the large number of hydrocarbon. By adding the ring-B monomer to the ring-A one, the chemical binding structure transformed into the tightly cross-linked Si-O-Si networks and lower hydrocarbon contents. Averaged pore diameter of the films derived from the ring-A was almost the same as the ring diameter of ring-A monomer. On the contrary, the pore diameter of the film derived from ring-B is larger than the original ring size of ring-B monomer, and its pore-size showed broad distribution probably due to partial breaking of the 8-membered ring. In other words, the chemical binding of the 6-membered ring (hexagonal structure) is more stable than that of the 8-membered one during the PECVD process. The mechanical property of the copolymerized SiOCH film is improved mainly by the cross-linked Si-O-Si network formation dissociated from the 8-membered one, bonding together the chemically stable 6-membered ring. The copolymerization with sub-nanometer Si-O ring is useful technique for highly reliable Cu interconnects toward 32nm-node and beyond.