L. Jay Guo University of Michigan
Ghassan E. Jabbour Arizona State University
John A. Rogers University of Illinois, Urbana-Champaign
Shu Yang University of Pennsylvania
Magnus Berggren Linkoping University
N1: Organic Electronic and Photonics I
L. Jay Guo
Tuesday PM, April 10, 2007
Room 2003 (Moscone West)
9:00 AM - N1.1
Printed Multilayer Superstructures of Aligned SWNTs for High Performance Electronics.
Seong Jun Kang 1 , Coskun Kocabas 2 , John Rogers 1 Show Abstract
1 materials science and engineering, university of illinois at urbana champaign, Urbana, Illinois, United States, 2 Physics, university of illinois at urbana champaign, urbana, Illinois, United States
9:15 AM - N1.2
Film Transfer Printing Technique for Multilayered Conjugated Polymer Structures
Keng-Hoong Yim 1 , Zijian Zheng 2 , Ziqi Liang 2 , Wilhelm Huck 2 , Richard Friend 1 , Ji-Seon Kim 1 Show Abstract
1 Cavendish Laboratory, University of Cambridge, Cambridge United Kingdom, 2 Melville Laboratory for Polymer Synthesis, University of Cambridge, Cambridge United Kingdom
Solution-processability of conjugated polymers allows the use of relatively low-cost and simple film deposition techniques such as spin-coating for fabrication of organic semiconductor devices. However, the common solubility of many polymers in most solvents limits the fabrication of multilayered structures with abrupt polymer-polymer heterojunctions.We report a novel thin film lamination technique based on poly(dimethylsiloxane) (PDMS) stamp. This method utilises a sacrificial layer of water-soluble poly(styrene sulphonate)-doped poly(3,4-ethylene dioxythiophene) (PEDOT:PSS) to facilitate the transfer printing process. Here we demonstrate the versatility of this transfer printing technique using thin films of poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT). We have successfully transferred F8BT thin films over large area (3 inch Si wafer) onto virtually any substrates, including flexible poly(ethylene terephthalate) (PET) substrates or another polymer film to form multilayered structures. We found that the transfer printed F8BT film preserves the initial photoluminescence efficiency value, suggesting neither the film lamination process nor the sacrificial PEDOT:PSS layer causes significant degradation to the optical properties of the transferred film. This transfer printing technique is also shown to be applicable for films with uneven surfaces, such as imprinted F8BT nanowires or polymer blend films with micron-scale phase separated structures. We have fabricated bilayered polymer light-emitting diodes (LEDs) with poly(9,9-di-n-octylfluorene-alt-(1,4-phenylene-((4-sec-butylphenyl)imino)-1,4-phenylene) (TFB) and transfer printed F8BT as active layers. These LEDs show comparable electroluminescence efficiency as those fabricated with F8BT:TFB blend films, but exhibit more gentle efficiency decay at high voltages, which we attribute to smoother film surface that reduces leakage current. The balance of charge carrier injection can be further optimised by varying the relative thickness of the F8BT and TFB layers to spatially control the recombination zone. This novel transfer printing technique provides a promising lithography-less approach for low-cost, large area fabrication of multilayered conjugated polymer structures, which enables us to manipulate and further optimise device performance by appropriate charge and photon confinement via energy gap offsets across interfaces. This technique will create new window of opportunities for conjugated polymer-based devices, such as full colour polymer LEDs with three active layers of respective emitters, and electrically-pumped lasers with multilayered distributed Bragg reflector.
9:30 AM - **N1.3
Patterning of Organic Semiconductor Materials for High Performance Transistors
Zhenan Bao 1 Show Abstract
1 , Stanford University, Stanford, California, United States
Organic semiconducting materials are now being considered as the active materials in displays, electronic circuits, solar cells, chemical and biological sensors, actuators, lasers, memory elements, and fuel cells. The flexibility of their molecular design and synthesis makes it possible to fine-tune the physical properties and material structure of organic solids to meet the requirements of technologically significant applications. In contrast to inorganic materials, active organic thin films can be deposited at much lower substrate temperatures (less than 120 C) in low vacuum or atmospheric pressure environments. It has been demonstrated that low-cost deposition techniques such as solution spin-coating, casting, and even printing can be used for deposition of solution soluble organic materials. These processing advantages, together with the natural abundance of organic solids, make semiconducting organics attractive for large-area and low cost applications. The performance of OTFTs depends on the construction of each of the active layers, which are the organic semiconductor layer, insulating (dielectric) layer and the electrodes. The deposition method, condition, sequence, post-deposition treatment, and surface treatment significantly impact OTFT performance. Therefore, it is important to fully understand various factors that affect the thin film growth processes. Specifically, one needs to pay attention to how the molecular structure of the organic semiconductor and thin film morphology affect the performance of OTFT devices, namely, the field effect mobility and on/off ratio.In this talk, several methods for patterning of organic semiconductors will be discussed.
10:00 AM - N1.4
All-organic Electronic and Electrochemical Devices Printed on Paper.
Magnus Berggren 1 , David Nilsson 2 , Michael Logdlund 2 , Payman Tehrani 1 Show Abstract
1 ITN, Linkoping University, Norrkoping Sweden, 2 Printed Electronics, Acreo AB, Norrkoping Sweden
10:15 AM - N1.5
Unconventional Lithography for Channel Formation of Polymer Thin-Film Transistors.
Hyewon Kang 1 , Taegeun Kwon 1 , Hong H. Lee 1 Show Abstract
1 Chmical and biological engineering, Seoul National University, Seoul Korea (the Republic of)
We introduce a simple technique of soft molding in reverse (SMIR) for defining simultaneously both the active area and the channel in fabricating polymer thin-film transistors (TFTs). The technique is free from the ill effects associated with solution processing. It also allows one to define the channel length down to sub-micron range. The electrical characteristics of the device fabricated by SMIR are as good as the best obtainable with solution-processed polymer TFTs.
10:30 AM - **N1.6
Charge Injection across Self-Assembly Monolayers in Organic Field Effect Transistors: Odd-Even Effects.
Fabio Biscarini 1 , Pablo Stoliar 1 , Rajendra Kshirsagar 1 , Massimiliano Massi 1 , Dago de Leeuw 2 Show Abstract
1 Nanotechnology of Multifunctional Materials, CNR - ISMN, Bologna Italy, 2 , Philips Research Laboratory, Eindhoven Netherlands
11:30 AM - **N1.7
Controlling the Performance of Semiconducting Polymers for Printed Electronics
Michael Chabinyc 1 Show Abstract
1 Electronic Materials Laboratory, PARC, Palo Alto, California, United States
Organic materials are forming a new basis for the manufacture of electronic devices, such as displays, where they will be used as substrates and active materials. Flexible substrates present unique challenges for the fabrication and design of printed electronics. The electrical performance of thin-film transistors, TFTs, formed with printable semiconducting polymers is rapidly approaching that of amorphous silicon. The processing conditions that lead to the highest performance TFTs in prototype devices may be difficult to achieve in practice. We will discuss methods to control the electrical performance of semiconducting polymers within the constraints of current methods of fabrication. For example, the roughness of many dielectrics on flexible substrates approaches the length scale of the molecular dimensions of many semiconducting materials and has a strong influence on the field-effect mobility of polymeric transistors. X-ray scattering data shows that ordering in films of semicrystalline polythiophenes is nucleated from the surface suggesting that roughness can affect molecular ordering. We find that increasing surface roughness generally decrease the field-effect mobility of semiconducting polymers. The performance of transistors is also strongly affected by chemical functionalities at the surface of the gate dielectric. For example, hydrophilic surfaces generally produce TFTs with lower field-effect mobilities than hydrophobic ones. We will discuss our methods to use surface energies to control the feature-sizes in inkjet printing while still maintaining electrical performance.
12:00 PM - N1.8
Understanding the Selective Nucleation of Organic Single Crystals from Nanoscopically Rough Surfaces.
Stefan Mannsfeld 1 , Shuhong Liu 1 , Alejandro Briseno 2 , Zhenan Bao 1 Show Abstract
1 Department of Chemical Engineering, Stanford University, Stanford, California, United States, 2 Department of Chemistry and Biochemistry and Exotic Materials Institute, Department of Materials Science and Engineering, University of California-Los Angeles, Los Angeles, California, United States
Their high performance vs. production cost ratio makes organic single crystal transistors (OFETs) attractive for microelectronic applications such as sensor arrays or small-scale displays. More than thin film-based OFETs, single crystal OFETs appear very suitable for pixel/array-based electronic applications owing to their high performance and hence lower power consumption as well as the inherent absence of crosstalk between neighbouring devices. Previously, the hand-picking and subsequent placement of individual crystals on a device structure represented a severe limitation for producing single crystal-based OFET arrays at high density and with reasonable throughput. We recently reported a materials-general method of fabricating large arrays of patterned organic single crystals .
Microcontact-printed thick octadecyltrichlorosilane (OTS) film domains on an inert substrate surface (here SiO2) were found to act as preferential nucleation sites for single crystals of a variety of organic semiconductor materials such as pentacene or C60. Depending on the size of the printed OTS domain, multiple or individual single crystals can be grown. In order to understand the mechanism behind the preferential nucleation, the stamped OTS domains and the contact-plane between the OTS domains and the organic crystals were inspected by atomic force (AFM) and optical microscopy. It was found that the patterned contrast in surface topology (i.e. local roughness) is crucial to the observed selective nucleation of organic crystals.
References: A. L. Briseno, S. C. B. Mannsfeld, M.M. Ling, R. J. Tseng, S. Liu, C. Reese, Y. Yang, F. Wudl, Z. Bao, “Patterning Organic Single-Crystal Transistor Arrays” Nature, in press (2006).
12:15 PM - N1.9
Organic Field-Effect Transistors: Photogenerated Charge Transport.
Soumya Dutta 1 , K. Narayan 2 Show Abstract
1 , CNR-ISMN, Bologna Italy, 2 CPMU, JNCASR, Bangalore India
Organic field-effect transistors (OFETs) exhibit several interesting features other than usual switching performance under the influence of gate voltage. The use of OFETs in sensing activity has opened up several possibilities as far as application is concerned. The large photosensitivity of poly(3-alkyle thiophene)-based transistor has attracted considerable attention to use it as an active photodetector . The large change in conductance upon exposing to light, followed by a slow relaxation upon terminating the photoexcitation was explained on the basis of serial relaxation process due to a hierarchy of the systems with spatial separation of the photogenerated electrons and holes . The inherent slow dynamics of the photogenerated carriers in such configuration were exploited to observe the memory effect with repeated write, read, store and erase functions by using the appropriate combination of light and gate voltage (Vg) . The spectral profiles of the intensity modulated photocurrent at different Vg exhibited clear differences in the accumulated and the depleted mode of operation. The unique combination of voltage and light as the controlling parameters for charge transport in OFETs was also verified in intensity modulated spectral response of drain current (Iph). The results of Vg-controlled Iph revealed the effective region for photogeneration in this device structure. The spatial information of photogenerated charge carriers, which were also modulated by the gate voltage, was reported in case of optically transparent OFETs recently . We study these results and discuss the possibility of OFETs to be used as an active photodetector, operating in the entire visible range of spectrum.References: Narayan et al. Appl. Phys. Lett. 79, 1891 (2001). Dutta et al. Phys. Rev. B 68, 125208-1 (2003). Dutta et al. Adv. Mater. 16, 2151 (2004). Dutta et al. Appl. Phys. Lett. 87, 193505-1 (2005).
12:30 PM - N1.10
Laser based Low-temperature Lithographyfree High Resolution Inkjet Printed OFET(organic field effect transistor) Fabrication on Polymer Substrate.
Seung Hwan Ko 1 , Heng Pan 1 , Costas Grigoropoulos 1 , Dimos Poulikakos 3 , Christine Luscombe 2 , Amanda Murphy 2 , Jean Frechet 2 Show Abstract
1 Mechanical Engineering, University of California, Berkeley, California, United States, 3 Mechanical and Process Engineering, ETH, Zurich Switzerland, 2 Chemistry, University of California, Berkeley, California, United States
N2: Organic Electronics and Photonics II
Tuesday PM, April 10, 2007
Room 2003 (Moscone West)
2:30 PM - **N2.1
Engineering Conductive Polyaniline for Thin-Film Electronic Applications.
Joung Eun Yoo 1 , Kwangseok Lee 1 , Tracy Bucholz 1 , Lynn Loo 1 Show Abstract
1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States
Polyaniline (PANI) is considered an attractive conducting polymer for organic and polymer electronics due to its promising electrical, and optical properties, as well as environmental stability. In its emeraldine base form, PANI is an insulator. To obtain the conductive emeraldine salt forms of PANI, the emeraldine base is chemically doped by exposure to an acid. Our route to obtaining water-dispersible, conductive PANI starts with the oxidative polymerization of aniline in the presence of a polymer acid template. The polymer acid template serves two roles: in addition to doping PANI to produce the electrically conductive emeraldine salt forms, the excess pendant sulfonic acid groups can impart water dispersability to the material. The polymer acid of choice is poly(2-acrylamido-2-methyl-1-propane-sulfonic acid), or PAAMPSA. We find the electrical conductivity of PANI-PAAMPSA to increase with decreasing PAAMPSA molecular weight. Additionally, we can tune the electrical conductivity of PANI-PAAMPSA by varying the aniline to sulfonic acid molar ratio in the feed. The bulk conductivity of PANI-PAAMPSA peaks at a molar feed ratio of 1:2; solid-state NMR confirms that the polymer made at this molar feed composition has minimal structural defects. As such, charges are not localized along the PANI backbone. We have also template polymerized PANI on PAAMPSA that is narrow in molecular weight distribution (PDI ≤ 1.2; obtained by atom transfer radical polymerization). Compared to PANI that is template polymerized on PAAMPSA from conventional free-radical polymerization of comparable molecular weights (PDI ~ 1.5-1.7), these materials exhibit higher conductivities. Simultaneously, we observe drastic structural differences in these materials that correlate with changes in conductivity.From a device standpoint, we have successfully incorporated PANI-PAAMPSA source and drain electrodes in organic thin-film transistors. These devices exhibit saturation mobilities and on-off ratios that are comparable with analogous devices with gold source and drain electrodes. From a charge injection standpoint, PANI-PAAMPSA electrodes exhibit reduced contact resistance at the organic semiconductor-electrode interface compared to devices with gold electrodes. This observation is directly correlated with morphological changes on both the macroscopic and the molecular levels across the organic semiconductor-electrode interface in the two sets of devices.
3:00 PM - N2.2
Uniaxial Alignment of Liquid-Crystalline Conjugated Polymers by Nanoconfinement.
Zijian Zheng 1 2 , Keng-Hoong Yim 3 , Mohammad Saifullah 4 , Ji-Seon Kim 3 , Richard Friend 3 , Mark Welland 2 , Wilhelm Huck 1 2 Show Abstract
1 Department of Chemistry, University of Cambridge, Cambridge United Kingdom, 2 The Nanoscience Center, University of Cambridge, Cambridge United Kingdom, 3 Department of Physics, University of Cambridge, Cambridge United Kingdom, 4 , Institute of Materials Research and Engineering, Singarpore Singapore
We demonstrate the uniaxial alignment of a liquid-crystalline (LC) conjugated polymer, poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) by means of nanoconfinement during nanoimprinting, in which the imprinting mold had nanochannel arrays with 20 nm width. The orientation of the conjugated backbones was forced to align parallel to the nanolines imprinted into the polymer film. Polarized UV-vis absorption and photoluminescence spectra were measured to quantify the degree of alignment, showing that the polarization ratio and uniaxial m olecular order parameter were as high as 66 and 0.97, respectively. The aligned F8BT film was used as the active layer in a PLED, which resulted in polarized electroluminescence with a polarization ratio of 11.
3:15 PM - **N2.3
Printing-based Manufacturing of Polymer TFT's.
Henning Sirringhaus 1 Show Abstract
1 , University of Cambridge, Cambridge United Kingdom
Polymer transistors offer new opportunities for the controlled manufacturing of active electronic circuits by a combination of solution processing and direct printing. We will review recent progress towards manufacturing of high-performance organic transistor circuits by high-resolution printing techniques and discuss the device physics of such-solution processed devices, in particular the charge injection processes at the source-drain contacts.
4:15 PM - N2.4
Inkjet Printed Embedded Resistors.
Erik Moderegger 1 , Stefan Gamerith 2 , Horst Scheiber 2 , Martin Gaal 2 , Harald Plank 2 , Gernot Mauthner 2 , Emil List 2 Show Abstract
1 R&D, AT&S AG, Leoben Austria, 2 , Christian-Doppler-Laboratory for Advanced Functional Materials, Graz Austria
While inkjet printing is commonly known as a low-cost method of producing outputs of digitally stored information onto paper, the possibilities are far beyond. The technology has established itself as a tool for engineers and scientists because of its ability to finely dose liquid materials into precisely definable spots. Owing to these properties inkjet printing has found applications in electronics, optics, life sciences and countless other fields.When it comes to mass production of devices however, inkjet printing is still in its infancy. This is mainly due to the difficulties in the formulation of inks that allow for continuous operation over long periods of time.In this paper we discuss the demands on ink jet technology and ink formulation from our view as a leading producer of printed circuit boards. We will report on our results in ink and device development for the production of inkjet printed resistors embedded into the inner layers of printed circuit boards.
4:30 PM - N2.5
Liquid Electrophotographic Printing Process to Pattern Etch Masks for the Fabrication of Large Flexible Electronics.
Marcia Almanza-Workman 1 , Carl Taussig 1 , Udi Chatow 1 , Vincent Heesen 2 Show Abstract
1 , Hewlett-Packard Laboratories, Palo Alto, California, United States, 2 , Hewlett-Packard Company, San Diego, California, United States
4:45 PM - N2.6
Manufacture of Organic Electronic Components using Standard Printers/Proofers.
Henrik Sandberg 1 , Kaisa Lehtinen 1 , Salme Jussila 1 , Kristiina Rutanen 1 , Teemu Ruotsalainen 1 , Tomi Hassinen 1 Show Abstract
1 Printable Electronics and Optics, VTT Technical Research Center of Finland, Espoo Finland
Electronics are expanding into new fields where low-cost manufacture in large volumes is a deciding factor. There are visions of electronic functionality in single use items and every-day applications where one of the main aims is to increase product attractiveness and give a commercial edge and added value to the product. This has lead to the need of, and consequently the development of new methods for preparing electronic devices, utilizing solution processable materials and printing type deposition and patterning techniques.We present examples of electronic components where standard printing methods and table-top proofing devices have been utilized for sample preparation. The sample preparation methods demonstrate the applicability of standard printing technology, as well as their limitations, for the manufacture of basic electronic components, such as diodes and transistors, using conjugated polymers and soluble molecules. The main techniques applied are gravure and flexographic printing, and as a substrate flexible PET film is used. The issues involved in multilayer printing of conjugated polymers and other materials needed for electronic devices are addressed, for example in the case of organic transistors, the use of thermally or UV cross-linkable polymer insulators. As polymer semiconductor material commercial polythiophene based conjugated polymers are used.For comparison samples are made in parallel, where for example the electrodes are metallic, traditionally made by thermal vacuum evaporation. The resolution of the printing methods used as such is not sufficient for the required transistor channel dimensions in a standard OFET. Novel application areas as well as novel manufacturing techniques opens new possibilities for entirely new device concepts. The electronic components in a mass-produced printed circuit may work by completely new mechanisms. The gravure and flexographic printing methods are chosen as they allow for low-cost fabrication using organic material in solution and the process is easily scaled for high volumes even using existing printing machines.
5:00 PM - N2.7
Organic Field-Effect Transistors Fabricated by Microcontact Printing and Self-Assembly
Amare Benor 1 , Veit Wagner 1 , Dietmar Knipp 1 Show Abstract
1 Electrical Engineering, Intenational University Bremen, Bremen, Germany, Germany
Micro Contactprinting (μCP) of self-assembled monolayer (SAMs) in combination with selective surface wetting was used to realize radio frequency micro coils and pentacene thin film transistors for radio frequency information tags (RFID tags). The combination of micro contact printing and selective wetting/dewetting provides a universal route to pattern a variety of different materials including polymers and metal films. In our study we used the self-assembled monolayers (Octadecyltrichlorosilane (OTS), CH3(CH2)17SiCl3, which was printed on cleaned silicon or glass substrate. The printed monolayer leads to the formation of hydrophilic and hydrophobic regions, which facilitates the selective deposition of polymers or resists like Poly (methyl methacrylate), PMMA, on the hydrophilic regions. Following the selective deposition of a resist, a lift-off process was used to pattern gold and titanium metal thin films. This technique was applied to realize radio frequency (RF) coils and electrodes for pentacene thin film transistors. The techniques allows for patterning of electrodes down to 2mm. Transistors fabricated by this approach exhibit charge carrier mobilities of 0.2-0.4 cm2/Vs and on/off ratios of ~106. The influence of the printed process on the device properties will be described. In particular the influence of the contact resistance of the TFTs on the charge carrier mobility and the threshold voltage will be discussed. Finally, the electrical characteristic of pentacene TFTs prepared by printing will be compared with transistors prepared by conventional optical lithography.
5:15 PM - N2.8
Squares, Lines, and Circles: A Soft-Lithography Approach for Patterning Organic Semiconductor Transistors.
Alejandro Briseno 1 2 , Zhenan Bao 2 Show Abstract
1 Chemistry, University of Washington, Seattle, Washington, United States, 2 Chemical Engineering, Stanford University, Stanford, California, United States
In order to minimize cross-talk between neighboring devices, patterning of the active semiconductor layer is necessary. Cross-talk is a highly detrimental condition relating to the interaction between nearby devices, where operational characteristics of one device affect one or more adjacent devices in close proximity (e.g., via capacitive, inductive or conductive coupling). As devices are reduced to smaller scales, cross-talk issues can become more pronounced. One approach to reducing or minimizing cross-talk between neighboring devices involves separation of semiconductor materials, such as by patterning the active semiconductor layer. Patterning of organic semiconductors is also crucial for the fabrication of large arrays of devices and complex circuits. A desirable patterning method should be simple, high throughput, functional over a large area, and cause minimal degradation to the organic semiconductor and/or the device performance. Several printing methods have emerged as suitable candidates with results demonstrating adequate device performance (e.g., soft lithography, ink-jet printing, thermal laser transfer printing, selective dewetting, etc.). For instance, microcontact printing (μCP) has recently demonstrated high-resolution, large-area patterning onto flexible surfaces. In this presentation, we discuss a variety of methods developed in our laboratory for patterning semiconductor polymers, conducting polymers, and organic single crystals for fabricating arrays of transistor devices. In all our methods, we utilize soft-lithography (microcontact printing, μCP) for printing self-assembled monolayers (SAMs), oligomers, and polymer films for patterning organic semiconductors from solution and vapor-phase.
5:30 PM - N2.9
Effect of Annealing Conditions on Electrical Resistivity, Microstructure and Mechanical Properties of the Ink-Jet Printed Ag Electrodes.
Jung-Kyu Jung 1 , Soo-Hong Choi 1 , Myung Joon Jang 2 , Jae Woo Joung 2 , Young-Chang Joo 1 Show Abstract
1 School of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Central R&D Institute, Samsung Electro-Mechanics, Suwon Korea (the Republic of)
Use of ink-jet printing technology has been explored for fabrication of electronic circuits on various substrates. The prime advantage of ink-jet printing is its low-temperature processing, pattern-on-demand nature that does not require lithography or etching processes. Silver (Ag), the highest conductive metal, has been studied intensively for inkjet printing. However, ink-jet printing is a wet process. Therefore, contrary to the closely-packed microstructure of as deposited sputtered or evaporated films, "as jetted" Ag patterns are likely to have loosely-packed microstructure with small grain sizes and high porosity, similar to the microstructure of the sintered metal powder. Both the grain boundaries and pores work not only as important scattering sources for electron conduction but also affect the mechanical properties significantly. This means that the ink-jetted Ag films with small grain sizes and high porosity may have high electrical resistivity and inferior mechanical properties. The electrical resistivity is critical to the electrical performance of electrodes and the mechanical properties are important in mechanical reliability issues such as cracking, fatigue, or peeling-off during thermal treatment. We have characterized the effect of annealing conditions on the grain sizes and porosity and their effect on the electrical resistivity and thermo-mechanical properties of the ink-jetted Ag films. We observed the microstructural evolution of the ink-jetted Ag thin films on the polymer and the Si substrates under various annealing conditions using the field-emission scanning electron microscopy (FE-SEM). The electrical resistivity of those films was measured in-situ. The thermo-mechanical properties of the ink-jetted Ag films were also examined by the substrate curvature method. The grain growth was observed as we annealed the ink-jetted Ag films. The higher annealing temperature, the faster stagnation of grain growth with the larger grain sizes was found. The change in porosity was shown to have transitional temperature and time; at first the porosity increases and then decreases. Annealing with higher temperature and longer time, we got near-zero porosity films. The behavior of change in electrical resistivity was mainly dominated by grain growth rather than porosity. The change of electrical resisitivity was estimated using the porosity and grain boundary scattering model using the measured pore and grain boundary sizes. The changes in the thermo-mechanical properties of ink-jetted Ag films were dependent on both the grain size and the porosity. Our results show that the microstructure characterized by grain and pore distribution is most important in obtaining the ink-jetted Ag films that have lower electrical resistivity and higher mechanical reliability. The process conditions that result in the optimal microstructure are discussed and suggested.
5:45 PM - N2.10
Electrochemical Over-oxidation as a Patterning Technique for Printed Electronics.
Payman Tehrani 1 , Joakim Isaksson 1 , David Nilsson 1 2 , Nathaniel Robinson 1 , Lars-Olov Hennerdal 2 , Magnus Berggren 1 Show Abstract
1 Dept. of science and technology, Linköping University, Norrköping Sweden, 2 , Acreo AB, Norrköping Sweden
L. Jay Guo University of Michigan
Ghassan E. Jabbour Arizona State University
John A. Rogers University of Illinois, Urbana-Champaign
Shu Yang University of Pennsylvania
Magnus Berggren Linkoping University
N3: Nanoimprint and Applications
Wednesday AM, April 11, 2007
Room 2003 (Moscone West)
9:00 AM - N3.1
Pattern Transfer Process Using Innovative Polymers in Combined Thermal and UV Nanoimprint Lithography (TUV-NIL).
Francesca Brunetti 1 , Stefan Harrer 1 , Giuseppe Scarpa 1 , Paolo Lugli 1 , Mike Kubenz 2 , Christine Schuster 2 , Freimut Reuther 2 Show Abstract
1 institute for nanoelectronics, Technical University of Munich, Munich Germany, 2 , micro resist technology GmbH, Berlin Germany
9:15 AM - **N3.2
Step and Flash Imprint Lithography: A Progress Report.
C. Willson 1 Show Abstract
1 Chemical Engineering, The University of Texas, Austin, Texas, Texas, United States
9:45 AM - N3.3
Reversal Nanoimprint and Non-destructive Nano-metrology for Biomimetic Tissue Engineering Nanoscaffolds.
Wenchuang (Walter) Hu 1 , Adam Crouch 1 , Rayan Alassaad 1 Show Abstract
1 Electrical Engineering, University of Texas at Dallas, Richardson, Texas, United States
10:00 AM - N3.4
Silver Direct Nanoimprint for Photonics.
Stefano Buzzi 1 , Jorg Loeffler 1 Show Abstract
1 Department of Materials, ETH Zurich, Zurich Switzerland
Metal-containing optical devices are attracting increasing interest because of their improved or even new properties. To fabricate low-loss devices, strict requirements must be fulfilled in terms of metal purity, size and shape of the structures. In this contribution, direct nanoimprint (microforging) of silver is investigated as a promising fabrication approach. A metal film is put on the structured dielectric and inserted into the structures by mechanical deformation. The dielectric material can act as a mold and be removed after processing to release the structured metal, or it can form part of the optical device. To evaluate the feasibility of this method, holes and lines of various sizes (0.25 – 4 μm) and aspect ratios (0.5 – 5) were etched into silicon wafers using dry etching techniques. The resulting metallic structures were observed by high-resolution SEM, and cross-sections of the filled silicon wafers were prepared using a focused ion beam (FIB) system. The microforging process was also performed at elevated temperatures, exploiting recovery phenomena such as dynamic recrystallization. In this case, the structures were successfully filled over a large surface ( > 1 mm2), independently of size, aspect ratio and wall roughness. The silver accurately reproduced even the smallest surface morphology of approximately 20 nm. Optical and mechanical properties of the silver micropillars will be discussed.
10:15 AM - N3.5
3D Photonic Structures by Sol-Gel Imprint Lithography.
Marc Verschuuren 1 , Hans Sprang 1 Show Abstract
1 Photonic Materials and Devices, Philips Research, Eindhoven Netherlands
3D photonic band gap materials can, ideally, be used to confine and redirect light, on the scale of an optical wavelength. A so-called “ wood-pile” structure, consisting of aligned crossed bars, is an efficient option for realising these goals, because a full band gap is obtained at a moderate refractive index contrast between the bars and the environment. . A wood-pile structure is also interesting from a fabrication point of view, because of the relatively simple layout.This work aims at the development of a novel method for making a free-standing stack of crossed silica bars on a substrate, using only minimal process steps. We report on the preparation of up to 6 layers of crossed bars of 70x70 nm2 with a 240 nm pitch, over areas up to 1 cm2, by imprinting a sol-gel material. The final cross bar structure consist of quartz-like material, which can be heated up to 1000 °C. This allows for subsequent filling with a high refractive index material, using e.g. chemical vapour deposition, in order to obtain an optical band gap. For a wood-pile structure to exhibit its maximal possible band gap, each layer has to be accurately aligned with respect to the previous ones.Inorganic imprint resists (like sol-gel materials) are not widely used, as these materials usually suffer high shrinkage and as a consequence features lose their shape.  Shape retention has been considerably improved by using specific silicon precursors. This system can be imprint-patterned at room temperature by spincoating a thin sol-gel layer and application of a structured stamp to the sol-gel layer. The sol-gel is left to crosslink and after gelation the stamp is removed and the solid layer is cured. The thin residual layer at the bottom is removed by a reactive ion etch. To planarize the layer before depositing the next layer of bars, a solution of polystyrene is applied. The solvent is allowed to evaporate and the sample baked at 150 °C. At this temperature the polystyrene melts and de-wets the top surface of the structured bars, retracting to fill the gaps in between. This leaves a flat surface, within 5 nm, for the next layer. This procedure is repeated for the subsequent layers. After deposition of the last layer, the polystyrene can be removed. Examples will be shown of up to 6 layers of crossed silica bars with air in the spaces between the bars.*This work has been partly sponsored by the Dutch NanoNed program, grant ZMM7127. Boris Gralak and Michiel de Dood, Phys Rev E 67, 066601, 2003 Christian Marzolin, Stephen P. Smith, Mara Prentiss, George M. Whitesides. Adv. Mater. 1998, 10, 571.
11:00 AM - N3.6
Roll-to-roll Nanoimprint Lithography on Flexible Web
Se Hyun Ahn 1 , L. Jay Guo 2 Show Abstract
1 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, United States
Nanoimprint lithography (NIL) is considered as one of the most promising and competitive technologies for high throughput and low cost nanopatterning . However, the current process and throughput in NIL (~10 min or longer per Si wafer) is still far from meeting the demands of many practical applications, especially in the area of organic electronics and biotechnologies. To meet these demands, faster and more economical fabrication method is necessary. A continuous Roll-to-Roll imprint technique could provide a solution for large-area nanoscale patterning with greatly improved throughput; furthermore, it could overcome the challenges faced by conventional NIL in maintaining pressure uniformity and successful demolding in large area printing.The concept of roller imprinting was previous presented by Chou group . But the process that was demonstrated was to imprint a small piece of Si mold onto a Si substrate, which is not too different from that of conventional NIL, except a roller was used to apply pressure rather than a flat platen. The speed of printing was very low (0.5~1.5 cm/min) due to long heating/cooling cycle and the slow filling of high-viscosity thermoplastic polymers. True roll-to-roll nanoimprinting has been a challenge to community because it requires a complete set of solutions to address a number of interrelated material issues. In this work, we present true continuous imprinting of nanoscale structures (300nm line width grating) on a flexible web. Our new process uses a flexible fluoropolymer mold fixed to a roller and a UV curable liquid resist material. The pressure for NIL is solely from web tension. Faster process is possible because no thermal cycle is engaged and the low viscosity resist precursor can easily fill into the mold cavity. Thus, the imprinting throughput, i.e., the web speed, mainly depends on the curing time of resist, which is within a few seconds and could be further reduced by adjusting resist formulation. We will discuss in detail the material requirement that made this process successful and also suggest a number of potential applications.  S.Y. Chou, P. R. Krauss, P. J. Renstrom, J. Vac. Sci. Technol. B 14 (6), 1996 H. Tan, A. Gilbertson, S. Y. Chou, J. Vac. Sci. Technol. B 16 (6), 1998.
11:15 AM - N3.7
Solid State Electrochemical Nanoimprint.
Keng Hsu 1 2 , Peter Schultz 1 2 , Nicholas Fang 1 2 , Placid Ferreira 1 2 Show Abstract
1 Mechanical Science and Engineering, University of illinois at U-C, Urbana, Illinois, United States, 2 , Center for Nanoscale Chemical-Electrical-Mechanical Manufacturing Systems (Nano-CEMMs), Urbana, Illinois, United States
We report a novel nanoimprint approach based on solid state electrochemical electrode reactions. Using molds made of solid ionic conductors, this electrochemical imprinting process is capable of directly engraving and etching nanoscale features into metal substrates. To validate the concept, a silver sulfide electrolyte was synthesized and used as the mold material. Imprinting is performed by bringing the patterned Ag2S mold in contact with a silver substrate, and applying an external electrical potential across the mold and the substrate. The resulting electrochemical reaction dissolves silver at the contact areas between the mold and the substrate. With minimal process parameter optimization or control, this direct patterning technique was able to produce high-resolution features (down to 50 nm line width). The patterning rate of around 4nm/sec was achieved, and little mold degradation was observed in 10 repetitions of imprinting. Shown in Figure 1 is the SEM and reflection image of the fractal nanoantenna made with this solid state electrochemical nanoimprint technique. The smallest width of the fractal antenna is 90nm, allowing strong extinction of incident light.This solid state electrochemical nanoimprint process has the potential to achieve single-step transfer of nanoscale features directly into metals. Integrated with positioning, registration and sensing systems, this imprint technique offers new pathways to an economical, high throughput, large-area process for patterning metallic films for applications such as interconnects, chemical sensors and photonic structures.(Figures were not able to be uploaded with this system)
11:30 AM - N3.8
Patterning Polymers and Metals using Nano-Contact Molding Lithography
Kenneth Carter 1 , Sarav Jhaveri 1 Show Abstract
1 Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts, United States
We have developed a new lift-off process for patterning silicon/silica surfaces created using nanocontact molding lithography (NCM) via the use of a selectively soluble polymeric transfer layer. The use of an alcohol-soluble resin underlayer (ASR) for imprint lithography gives us a distinct processing advantage since we can successfully spin coat multiple layers on top of ASR thin films and when necessary strip it off easily using methanol as the solvent. This lift-off strategy allows us to easily fabricate patterns of metals and polymers on silicon surfaces. The sturdiness of the ASR films in various common non-alcohol organic solvents used for spin coating of polymeric and organic layers, such as THF and PGMEA, allows us to use these solvents during the fabrication steps of coating, imprinting and washings without affecting the ASR film. The patterning of an acrylate-based photopolymer on the surface of the ASR film was made possible by reacting the ASR film surface with methacrylate based silane to modify the surface for the contact molding process. As an example, we have shown the fabrication of metallic nanopatterns via this lift-off imprint lithographic technique. The process has 5 basic steps, (1) spin coat the ASR layer, (2) apply and pattern the photopolymer layer via UV-assisted imprint lithography [NCM], (3) plasma etch pattern through the ASR, (4) deposit metal film, and (5) develop in alcohol solution with lift-off of ASR resin and overlayers, leaving patterned metal layers. We have also shown that it was possible to use the ASR as a “top layer” for spin-coating onto thin polymer films, such as poly(dihexylfluorene), and using similar NCM process on the ASR layer followed by etching and lift-off, enabled us to the fabricate “positive” patterns of the polyfluorene polymer onto the silicon substrate.
11:45 AM - N3.9
Mechanical Stability of Polymeric Nanostructures: An Atomic Force Microscopy Study on Patterns Fabricated by Nanoimprint Lithography.
Huagen Peng 1 , Yen Peng Kong 2 , Albert Yee 1 2 Show Abstract
1 California Institute for Telecommunications and Information Technology, University of California Irvine, Irvine, California, United States, 2 Chemical Engineering and Materials Science, University of California Irvine, Irvine, California, United States
12:00 PM - N3.10
Simulation and Design of Planarization Materials for Reverse-tone Step and Flash Imprint Lithography.
Michael Lin 1 , Huang-Lin Chao 2 , Jianjun Hao 3 , Kyle Osberg 1 , Kane Jen 1 , Saul Lee 1 , C. Willson 1 Show Abstract
1 Chemical Engineering, The University of Texas at Austin, Austin, Texas, United States, 2 Mechanical Engineering, The University of Texas at Austin, Austin, Texas, United States, 3 Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas, United States
The step and flash imprint lithography (SFIL) process offers a low-cost alternative to traditional optical lithography for the patterning of sub-micron structures. The process involves dispensing a low-viscosity, photocurable monomer known as etch barrier onto a substrate and bringing a transparent template into contact with the liquid. The etch barrier fills the patterns on the template through capillary action, and the material is then photopolymerized by UV light. The template is separated from the polymer, leaving a solid replica of the template on the substrate. Various etch steps are then used to transfer the pattern into the underlying substrate. The mechanical nature of the SFIL process allows for the patterning of nanostructures beyond the limitations set by light diffraction in the optical systems. The resolution limit is ultimately set by the template patterning process.SFIL-R, a reverse-tone variant of the SFIL process, has been shown to be more tolerant than traditional SFIL towards post-process etch problems, such as faceting and non-uniform etch rates from pattern density gradients. In order to reverse the final pattern, a silicon-rich, photocurable film layer that serves as an etch mask is applied over the patterned etch barrier. This process is usually accomplished through traditional spincoating methods. During spincoating, surface forces coupled with the underlying topography can cause a conformal or semi-conformal film coating leading to the formation of a non-planar etch mask. Subsequent etching of this non-planar film can lead to poor pattern transfer. Therefore, the need to understand the forces governing the planarization process on the sub-micron level is critical for SFIL-R.This paper focuses on the design of materials and simulation of the formation of planarization layers in SFIL-R. More specifically, the leveling of non-volatile, Newtonian fluids over large, isolated topography is studied in detail through modeling and experimentation. The concept of the critical degree of planarization (DOPcrit), which determines the extent of leveling required for satisfactory pattern transfer, is reviewed. A full-process simulation that models the leveling of films from spincoating to UV exposure is introduced as a method of studying DOPcrit , the corresponding leveling time (Tcrit), and how these parameters are influenced by material and topographic properties. Finally, experimental results for a novel SFIL-R planarization material developed at the University of Texas are presented and discussed.
12:15 PM - **N3.11
Nanometer-Scale Polymer Flow during Thermomechanical Data Storage and Imprint Lithography.
William King 1 Show Abstract
1 Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
This talk describes measurements and simulations of nanometer-scale polymer flow during thermomechanical data storage and nanoimprint lithography. The measurements employ either a heated atomic force microscope (AFM) cantilever tip that forms indents in a thin polymer film, or a nanoindentor tip that has been machined with focused ion beam and instrumented with an internal heater. The experiments find the relationship between time, temperature, and force required to deform polymer at the nanometer scale. The simulations use a finite-element approach that can accurately account for steep temperature and viscosity gradients in the polymer.
12:45 PM - N3.12
The Lift-off Technique for 20GHz Surface Acoustic Wave Filter
Nian-Huei Chen 1 , Chen-Liang Liao 1 , Henry J. H. Chen 2 , Chun-Hung Lin 3 , Fon-Shan Huang 1 Show Abstract
1 Electrinics engineering, National Tsing Hua University, Hsinchu Taiwan, 2 Electrical Engineering, National Chi Nan University, Nantou Taiwan, 3 , National Nano Device Laboratories, Hsinchu Taiwan
Wireless communications is the technology employed in systems such as cellular phones, local area networks, and mobile communication. There is great demand for higher operation frequency up to 10GHz. For central frequency 10GHz of surface acoustic wave (SAW) filter, the critical dimension of interdigital transducer (IDT) is down to 200nm with 50% metallization ratio. Step and flash imprint lithography (SFIL) can adequately offer mass production technique on IDT lithography. High aspect ratio of PR patterned by SFIL is the key technique for lift-off process. In this work, the HSQ template with high aspect ratio is patterned by direct electron beam writer (Leica E-beam Weprint 200) with beam size 20nm with low dose (360μC/cm2) and novel heating cycle. After transferring deep pattern on UV-resists with SFIL, we develop aluminum nanowire lift-off process with single-layer resist. Finally, SFIL is applied to produce SAW filter with aluminum nanowire about 90nm in linewidth and space ratio of 1:1 using lift-off process on AlN/SiC substrate. The central frequency will be as high as 20GHz. For high aspect ratio HSQ template fabrication, we use heat treatment serving as e-beam irradiation to transform caged structure into network in HSQ. The e-beam dose is therefore reduced. Then proper TMAH concentration and etching time are utilized to obtain perfect vertical sidewall. Diluted HSQ mixed with MIBK with ratio of 2:1 was first spin-coated on ITO(120nm)/Glass substrate. HSQ thickness is about 350nm. A low dose e-beam 360μC/cm2 combined with step-like heating cycle was used to transfer HSQ film into network form structure. Then HSQ films were developed by different TMAH concentration (5 ~25%) with etch time (3~20s) and post-expose bake temperature (160~260°C). HSQ template with various width/space, 1:1, 1:3, 1:10, for line width 100nm, 75nm, 80nm were then fabricated, respectively. After another step-like heating cycle, HSQ UV-template with smooth surface morphology, high transmittance and high hardness can be obtained. For UV-curable nanoimprint, release layer (F13-TCS) is coated on HSQ template. HSQ patterns can be transferred by Nanonex 2000 on PR (PAK-01-200) at room temperature with low pressure (5~15psi). Then residual resist layer under the trench were etched by RIE. Deposition of aluminum was done by thermal evaporation followed by lift-off. Aluminum nanowire were then formed. UV spectrophotoscopy and nanoindentor were used to examine the transmission and hardness of HSQ template, respectively. From transmission spectrum, it shows 90% transmission at 400nm. The value of hardness can be obtained from load-unload indentation results, 19GPa, higher than the hardness of conventional SFIL quartz template, 9GPa. The SEM images depict the fabricated templates, imprinted features and aluminum nanowire after lift-off process. We also use four point probe measurement method to obtain resistivity of aluminum nanowire.
N4: Printing of Biomolecules
Wednesday PM, April 11, 2007
Room 2003 (Moscone West)
2:30 PM - N4.1
Microcontact Printing of Cytophilic Proteins for Cell Patterning.
William Jo 1 , Yoojin Oh 1 Show Abstract
1 Physics, Ewha Woman Univ., Seoul Korea (the Republic of)
2:45 PM - N4.2
Microcontact Patterning of T4 Bacteriophages for Highly Specific Bacterial Detection.
Luc Gervais 1 , Murat Gel 1 , Beatrice Allain 2 , M. Tolba 3 , Luba Brovko 3 , M. Zourob 2 , Rosemonde Mandeville 2 , Mansel Griffiths 3 , Stephane Evoy 1 Show Abstract
1 Electrical and Computer Engineering, University of Alberta and Canadian National Institute for Nanotechnology, Edmonton, Alberta, Canada, 2 , Biophage Pharma Inc. , Montreal, Quebec, Canada, 3 Canadian Research Institute for Food Safety, University of Guelph, Guelph, Ontario, Canada
3:00 PM - **N4.3
Single Molecule Printing with Biomolecular Nanowires Complexed with Luminescent Conjugated Polyelectrolytes
Olle Inganas 1 , Anna Herland 1 , Per Bjork 1 , Ivan Scheblykin 2 , Ralph Hania 2 , Jens Andersson 1 Show Abstract
1 IFM, Linköpings Universitet, Biomolecular and organic electronics, Linkoping Sweden, 2 Chemical Physics, Lund University, Lund Sweden
The limits to printing are found in printing of single molecules, an interesting topic for nanopatterning. Printing of biomolecules and detector of biomolecules s is one approach towards biochips, and therefore relevant for genomics and proteomics. Single molecules may act as the point of growth of molecular size objects by self assembly, and molecules with an identity are therefore of interest. We have used classical molecular combing technique to stretch align DNA chains, or protein nanowires formed by misfolding of proteins, on elastomeric stamps, which are then used to transfer these chains onto another surface. The DNA nanowires are truly molecular chains, with length/width (L/W) ratio ≈104. Protein nanowires formed by misfolding of native proteins such as insulin are ten times thicker, with smaller L/W ratio. These objects are complexed with conjugated polyelectrolytes, or alternatively small luminescent intercalators which renders the object luminescent and visible, when forming a submonolayer of fully elongated and aligned objects on the micrometer dimension. The length of the lambda-DNA chains (≈25 µm] make these objects easily detected in optical microscopy; they are equally well imaged in scanning force microscopy, to measure the width and thickness of the wires. With single molecule spectroscopy methods, we can follow the emission from specific sites of complexation. We find the light emitted to be polarised and aligned to the stretched DNA molecule; the same holds true for the protein nanowires.
3:30 PM - **N4.4
Engineering Patterned Surfaces to Study Cellular and Multicellular Structure-function Relationships.
Ravi Desai 1 , Srivatsan Raghavan 1 2 , Christopher Chen 1 Show Abstract
1 Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States
4:30 PM - N4.5
Fabrication of Piezoelectric Polyvinylidene Fluoride (PVDF) Microstructures by Soft Lithography for Tissue Engineering and Cell Biology Applications.
Daniel Gallego 1 , Nicholas Ferrell 1 , Derek Hansford 1 Show Abstract
1 Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States
4:45 PM - N4.6
Patternable Integration of Living Cells with Self-Assembled Nanomaterials.
Eric Carnes 1 , Carlee Ashley 1 , DeAnna Lopez 1 , Cynthia Douthit 1 , Shelly Karlin 1 , Jennifer Pelowitz 1 , Hattie Gresham 1 , Graham Timmins 1 , C. Brinker 2 1 Show Abstract
1 , University of New Mexico, Albuquerque, New Mexico, United States, 2 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Patternable cell immobilization is an essential feature of any solid-state device designed for interrogating or exploiting living cells. Immobilized cells must remain viable in a robust matrix that promotes fluidic connectivity between the cells and their environment while retaining the ability to establish and maintain necessary chemical gradients. A suitable inorganic matrix can be constructed via evaporation-induced self-assembly of nanostructured silica, in which phospholipids are used in place of traditional surfactants as the structure-directing agents in order to enhance cell viability and to create a coherent interface between the cell and the surrounding three-dimensional nanostructure. We have developed several distinct cell immobilization and patterning strategies that have tailorable properties; the validity of each patterning method has been demonstrated with Gram-positive and Gram-negative bacteria, yeast, and mammalian cells. Biocompatible selective wetting techniques are used, as well as aerosol deposition and ink-jet printing. Viability of immobilized cells with respect to the different patterning techniques has been assessed. Transport of various biomolecules, such as sugars, proteins, and lipids, between the cells and their environment has been studied. Ability of the immobilized cells to establish relevant chemical gradients, such as pH or signaling molecules, has been characterized. Cell to cell communication within the matrices has also been investigated. With many of these patterning techniques, cells are also able to actively integrate into the host matrix by means of local process similar to the cell-directed assembly process we recently reported (Science 21, July 2006). This active integration of cells into a host matrix not only provides enhanced viability, but also provides a unique way of integrating bio- and nano-materials. In this instance, a nanomaterial with bulk functional properties can serve as a host matrix, maintaining its functionality while patterned cells create their own microenvironments. This provides not only new platforms for cellular interrogation, but also a novel yet simple procedure for creating new bionanomaterials.
5:00 PM - N4.7
Fabrication of Cell Containing Structures by Inkjet Printing.
Brian Derby 1 , Rachel Saunders 1 3 , Louise Carney 1 3 , Anne-Marie Buckle 3 , Gerard Markx 2 Show Abstract
1 School of Materials, University of Manchester, Manchester United Kingdom, 3 Faculty of Life Sciences, University of Manchester, Manchester United Kingdom, 2 School of Chemical Engineering and Analytical Sciences, University of Manchester, Manchester United Kingdom
The hematon is defined as the primary fundamental unit of haematopoiesis, the formation of blood cells. The precise composition and operation of the hematon is still unknown. One route to understanding the role of the hematon in the formation of blood cells is to fabricate an artificial cell-containing structure to mimic its architecture. We are using inkjet printing to achieve this aim.The hematon is believed to be a complex multicellular structure with dimensions 1n the range 200 - 500 μm. Structures of this scale comprising of human cells or human-derived cell lines embedded in an alginate matrix have been fabricated by ink-jet printing. Cell viability post-printing has been assessed using conventional biochemical assays to determine the fraction of cell death and cell metaboliC activity post-printing. 3-dimensional cell-containing structures hyave been printed with heterogenous cell populations and distributions.
5:15 PM - N4.8
Laser Direct-write Printing of Genetically Engineered Stem Cells for Tissue Engineering Applications.
Nicholas Kattamis 1 , Priscilla Purnick 2 , Ron Weiss 2 , Craig Arnold 1 2 Show Abstract
1 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States, 2 Electrical Engineering, Princeton University, Princeton, New Jersey, United States
5:30 PM - N4.9
3-D Biological Laser Printing for Application in Regenerative Medicine.
Christina Othon 1 , Xingjia Wu 2 , Juanita Anders 2 , Bradley Ringeisen 1 Show Abstract
1 , Naval Research Laboratory, Washington, District of Columbia, United States, 2 Department of Anatomy, Physiology & Genetics, Uniformed Services University of Health Sciences, Bethesda, Maryland, United States
Cell printing has been popularized recently as an important new tool for tissue engineering. Biological laser printing (BioLP) is one such tool which has demonstrated the ability to print three dimensional cell and biomolecular patterns on the micron-scale into a biopolymer matrix.  BioLP uses a thin oxide layer to absorb the laser pulse. The absorbed energy vaporizes the target layer, jetting a small volume (picoliter) of cell solution onto a receiving substrate. Previous studies demonstrated nearly 100% cell viability and retained phenotype/genotype post printing.  The technique allows for a small number of cells to be precisely printed with no evidence of heat shock or sheer stress.  We have used BioLP to print complex 2D and 3D patterns of growth-promoting olfactory-ensheathing cells (OECs) to guide axon growth in an in vitro
environment without the use of mechanical guides or lithographic tools. Previous studies have shown that injection of OEC solution into spinal cord injury sites support axonal regeneration and functional recovery in vivo
.  The specific method by which OECs promote axon regeneration is not known, however the secretion of neurotrophic factors is believed to be one possible mechanism.  By using printed scaffolds of patterned OECs rather than using an injected cell solution, cellular and biochemical signal channels are created that mimic the natural three-dimensional structure of the neural pathway. We hypothesize that these signal channels could be used to provide a continuous, directed, and sustainable source of growth promoting molecules to enhance and guide axon growth. In addition, OEC counts as low as 25,000 have been harvested from adult Sprague Dawley rats, making it crucial to utilize a low load volume printing technique, such as BioLP, to print the cells into 3D patterns. The high resolution printing of low-yield cells is an important advancement for in vitro
study of cell interactions and scaffold design for regenerative medicine.
 J. A. Barron, P. Wu, H. D. Ladouceur, B. R. Ringeisen, Biomedical Microdevices 6, 139 (2004).
 C. Y. Chen, J. A. Barron, B. R. Ringeisen, Applied Surface Science 252, 8641 (2006).
 A. Ramon-Cueto, F. Valverde, Glia 14, 163 (1995).
 M. T. Moreno-Flores, et al. Journal of Biomedicine and Biotechnology 2, 37 (2002).
5:45 PM - N4.10
Jan Sumerel 1 Show Abstract
1 , Dimatix, Santa Clara, California, United States
Unlike thermal ink jetting that uses heat to generate fluid ejection from a nozzle, MEMS-constructed piezoelectric ink jet printheads uses a thin PZT slab bonded to a silicon diaphragm to generate acoustic energy that drives drop formation without heat. Piezo-based ink jet printers are reliable, productive laboratory tools particularly where expensive materials are involved. As bioengineers, we are capitalizing on the ability of piezo-based drop-on-demand ink jets printers to precisely deposit a wide variety of biologically active materials to create custom arrayed patterned libraries. We are capitalizing on this nondestructive printing process to immobilize biologically active materials, and we have used this new processing technology for high throughput applications and array fabrication. These applications and many others take advantage of ink jet strengths as an additive, non-contact process. We have developed disposable ink jet cartridges and a laboratory bench-top printing system. We have printed many biological materials, and optimization of ink compositions has been the focus of our research. At this conference, I will discuss both solvent-based and aqueous bioinks. We will show the spatial deposition of both nanoinks and microinks and show the resulting biomaterial designs and arrays including DNA, bacteria, proteins, nanospheres and carbon nanotubes. We have printed gold nanoparticles and protein-bound nanospheres to allow patterning of fluorescent proteins. We have also printed carbon nanotube scaffolds for DNA. I will discuss ink composition and printing characteristics of these materials and the wave form parameters required for printing a broad range of aqueous materials used in the biosciences. We will also discuss using crystal quartz microbalance for accurate measurement of fluid delivery.
L. Jay Guo University of Michigan
Ghassan E. Jabbour Arizona State University
John A. Rogers University of Illinois, Urbana-Champaign
Shu Yang University of Pennsylvania
Magnus Berggren Linkoping University
N5: Emerging Printing Technologies
Thursday AM, April 12, 2007
Room 2003 (Moscone West)
9:00 AM - **N5.1
Combining Large and Small Area Patterning of 3D Optically Active Structures: Holography, Multiphoton Polymerization, and Self-Assembly.
Paul Braun 1 Show Abstract
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
A number of approaches, including holography and self-assembly have been proposed as pathways to large area periodic structures, however in many cases, simple periodic structures are not sufficient. It remains unclear how to add function to such structures in an efficient fashion, be this the introduction of aperiodic features, functional materials, or active components. In a specific example of our recent work in this area, we have now demonstrated the 3D waveguiding of light through a directly written defect embedded in a self-assembled photonic band gap material. With the goal of creating structures with increasing complexity and functionality, we have demonstrated the direct two-photon phase mask patterning of inorganic photoresists, resulting in complex, thermally stable 3D ceramics structures. This system is also compatible with multiphoton direct writing should embedded aperiodic features be of interest. One clear application for large area optically active structures where robust structures containing both periodic and aperiodic structures will be of interest is solar energy harvesting, and significant strides are being made in this direction.
9:30 AM - N5.2
Nanoimprinted Semi-Transparent Metal Electrode for Organic Solar Cell Applications.
Myung-Gyu Kang 1 , Myung-Su Kim 2 , Jae Cheol Cho 2 , Jinsang Kim 2 , L. Jay Guo 1 Show Abstract
1 Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Organic photovoltaics(OPVs) offer a promising alternative to inorganic photovoltaics due to low cost, easy fabrication, and compatibility with flexible substrate over large area. As a transparent electrode in OPVs, Indium Tin Oxide (ITO) is the predominant choice because it offers low electrical resistivity as well as good transmittance in the visible. However, it is getting more expensive and chemically problematic because of indium element. Furthermore, the conductivity of the ITO is not sufficiently high, which limits the fill-factor of OPVs. Therefore, it is questionable whether ITO is the optimum choice for transparent electrode. In this work, we propose and present a scheme to fabricate semitransparent metal electrode in the form of nanoscale periodically perforated metal film and evaluate its potential as transparent electrode for OPVs. By using semitransparent metal electrode we can eliminate problems associated with ITO and exploit the work function of the anode by choosing different metals for higher performance.The semitransparent metal electrode consists of periodically perforated rectangular or square shape holes fabricated by Nanoimprint lithography. This grid pattern on the imprinting mold was created by nanoimprinting twice using a grating mold, followed by reactive ion etching to create SiO2 molds. For rectangular shape grid mold, grating molds with different periodicity were used. The perforated metal electrodes were fabricated by nanoimprinting using such molds, metal deposition, followed by a lift-off process. Transmittance through such nanostructured metal film (e.g. 40nm thick Au) can be as high as 80% with sheet resistance less than 8Ω/square, while for a non-patterned metal film with the same thickness it is 10% or less. We show that the transmittance can be increased by reducing metal linewidth and the sheet resistance can be decreased by using thicker metal without sacrificing transmittance much.OPVs were then fabricated using the semitransparent metal film as transparent electrode. After UV-ozone cleaning of the patterned substrate surface, thin layers of PEDOT:PSS and P3HT:PCMB 1:1 were spin-casted on the nanostructured metal surface followed by baking. Finally, thermal evaporation of Al cathode through a shadow-mask completes the device fabrication. Electrical characterization of the OPVs made using nanostructured Au film as transparent electrode showed improved performance in terms of short circuit current and power conversion efficiency as compared with those made with conventional ITO electrodes. Optimization of polymer layer thickness and sheet resistance and transmittance of the semitransparent metal electrode for higher performance is currently underway. Our results indicate that such semitransparent metal structure could be used as a replacement of ITO.----------------  M. P. de Jong et al, Synth. Met. 2000, 110, 1. B. Maennig et al,: Organic p-i-n solar cells. Appl. Phys. A 79, 1 (2004).
9:45 AM - N5.3
Adhesion Promoting Photo-acid Generator APPAG - A New Class of Lithographic Material.
Robert Meagley 1 2 , Shalini Sharma 2 , Geeta Sharma 2 Show Abstract
1 Components Research, Intel Corp., Berkeley, California, United States, 2 MSD Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States
10:00 AM - N5.4
Nanoparticle Assembly and Charge Patterning by Contact Electrification.
Chad Barry 1 , Xinyu Wang 1 , Heiko Jacobs 1 Show Abstract
1 Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, United States
We report on a new nanocontact charging approach to pattern charge on insulating substrates that is based on contact electrification instead of using an external voltage pulse to charge a surface. The contact electrification is performed by bringing a functionalized, patterned, polydimethylsiloxane (PDMS) stamp into contact with an electret (PMMA or SiO2). The functionalization yields an increased electrostatic force of adhesion between the PDMS surface and the electret surface. Two contact charging mechanisms have been explored: hydrogen-ion transfer and dipoles-orientation where PDMS surface dipoles induce permanent dipoles in the electret upon contact. The PDMS stamp did not appear to loose it’s charging ability after several charging experiments, providing a repeatable process that allows multiple uses over a period of several days. Characterization of the surface by Kelvin Probe Force Microscopy shows highly charged surface areas with potentials in excess of 1V that occur at the locations of contact with the functionalized PDMS stamp. In addition, a gas phase assembly process was employed to position nanoparticles onto the highly charged areas with good selectivity at a resolution of <200nm. The contact electrification has specific applications in role-to-role nanoxerographic printers that exceed the size limitations of existing charging methods.
10:15 AM - N5.5
Hierarchical Assembly of High-aspect-ratio Nanopillar Arrays.
Ying Zhang 1 , Shu Yang 1 Show Abstract
1 Materials Science & Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
11:00 AM - **N5.6
Direct-Write Assembly of 3-D Micro-Periodic Photonic Crystals
Jennifer Lewis 1 2 Show Abstract
1 Materials Science and Engineering, University of Illinois, Urbana, Illinois, United States, 2 Materials Research Laboratory, University of Illinois, Urbana, Illinois, United States
We have developed a novel approach to patterning 3D micro-periodic structures via direct ink writing. Central to our approach is the creation of concentrated polyelectrolyte or sol-gel inks that flow through fine deposition nozzles and then "set" almost instantaneously to facilitate shape retention as they span gaps in underlying layers. By tailoring ink composition and rheology, we have created both polyelectrolyte scaffolds and sol-gel structures that possess a 3D micro-periodic architecture. In collaboration with the Braun group, we are using these polymeric scaffolds to template silicon or germanium hollow-woodpile structures via chemical vapor deposition. In parallel, we are creating sol-gel structures that can be directly converted into titania woodpile structures upon thermal annealing. The optical properties of each of these structures have been characterized. Efforts are now underway to introduce controlled defects into these photonic crystals and to reduce their characteristic feature size below 500 nm.
11:30 AM - N5.7
High Resolution Electron Beam Lithographic Deposition of Metal or Oxide Films from Metal Complexes.
Xin Zhang 1 , Ross Hill 1 Show Abstract
1 Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
In this paper, a method of direct electron beam lithographic deposition of metal or oxide films is demonstrated using metal organic complexes. In this method, a solution of a metal complex is used to spin coat a substrate to obtain a precursor film. The precursor film is then directly patterned by electron beam writing, leading to the decomposition of exposed area. A solvent developer is used to dissolve the unexposed area, leaving a negative pattern. Subject to further exposure or annealing, the pattern is converted into metal or metal oxide, depending on properties of the element and treatment conditions. Patterns of oxides of titanium, manganese, zirconium, and tantalum, and metallic gold were successfully obtained by direct electron beam writing with their organic complexes. Feature size of sub 100 microns was routinely achieved for systems studied. Feature size of 14 nanometers and resolution of 13 nanometers were demonstrated on a FEI 235 Strata Dualbeam (SEM/FIB) system. It was found that this method can be used to prepare patterns with an aspect ratio higher than 10. Positive electron beam lithography is also demonstrated in this paper.
11:45 AM - N5.8
Robust Printing and Dispensing Solutions with three Sigma Volumetric Control for 21st Century Manufacturing and Packaging.
Bo Li 1 , Kenneth Church 1 , Lance Swann 1 , Bryan Irwin 1 Show Abstract
1 , nScrypt inc, Orlando, Florida, United States
The trend for electronic industry to develop more functional, smarter and more compact devices has placed high requirements on the manufacturing and packaging process. One key technology to make these advancements possible is printing (or dispensing). However, the traditional printing techniques (e.g. pressure-timing needle dispensing, screen printing, pin transfer and jetting) have their own severe limitations such as dimensionality, accuracy, repeatability, flexibility and speed, which have become the bottle neck of the industry. Enabling tools and technologies/processes are greatly needed for producing conformal, highly integrated and complicated parts and assemblies. In this paper, nScrypt will present robust tool, novel pumping technologies and innovative printing/dispensing solutions for 21st century manufacturing and packaging, which specialized in precise volume control, accurate placement/alignment, conformal printing, and flexibility with materials and patterns. The capability of printing/dispensing volumes of pico liters as well as larger volumes with a variety of materials while maintaining precise placement in three dimensional spaces enables the manufacturing of fine-featured structures and the packaging of compact assemblies. Case studies of micro dots, resistors and dispensing on conformal surfaces will be presented with measurement and test results. The tool and process have a wide range of applications include, but not limited to, conductors, resistors, optics, adhesives, sealants, encapsulants, wire bonding, underfilling, and flip-chip bumping. They are also very suitable for bio material/structure printing.
12:00 PM - **N5.9
A New Soft-Lithography: Printing Solid Inks.
Ralph Nuzzo 1 Show Abstract
1 Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
It has now come to be understood that essentially any class of material can be rendered in a printable form. This statement will motivate the discussions developed in this talk. I will explore the progress being made in developing new forms of soft lithography that embrace this belief and emphasize embodiments related to the fabrication of diverse classes of devices. I will highlight specific applications related to novel form factor microelectronics, microfluidics for bioanalytical assays based on cellular cultures, and emerging opportunities for devices incorporating optical components sensing, imaging, amongst others. The utility of new forms made accessible by advances made in means of fabrication focus beyond the cost structures of these processes will be discussed.
12:30 PM - N5.10
Fabrication of µm-size Conductive Tracks by Laser Initiated Photo-reduction of Ink Jet Printed Silver Organometallic Deposits.
Jonathan Stringer 1 , Brian Derby 1 , Nuno Reis 2 Show Abstract
1 School of Materials, University of Manchester, Manchester United Kingdom, 2 Unidade de Investigação de Materiais Texteis e Papeleiros, Universidade da Beira Interior, Covilha Portugal
The manufacture of cheap, flexible electronic devices has potential for use in a number of areas including RFID tags, flexible displays and sensors. To produce such devices requires a technique that can fabricate electronic components on polymeric substrates with adequate resolution and functional properties. Such a process would ideally produce functioning electronic devices with approximately µm-size features at temperatures that will not affect the integrity of the polymer.Ink jet printing is a technique that shows promise for flexible electronics manufacture as it can simultaneously deposit pL-volume droplets of materials with different functionality, eliminating the need for masks or subtractive processing. The applicability of ink jet printing is limited both by the attainable resolution and any processing temperature needed for the printed deposit to obtain acceptable electronic properties. Typically, ink jet printing alone can produce feature of approximately 20-50 µm with processing temperatures of 150°C and higher.To further reduce both processing temperature and feature resolution of conductive tracks, ink jet printed organometallic silver deposits were subjected to a laser beam to initiate a photo-reduction reaction to silver. Fabricating conductive tracks in this manner showed no macroscopic heating of the substrate, and with the use of a micro-focus laser, feature sizes down to ~5 µm were obtained. Tracks produced in this way were characterised with regards to electrical properties, mechanical properties and microstructure. Comparison was made with similar tracks produced using a conventional heat treatment at 200°C. The influence of laser parameters (power, spot size and scan speed) on the above properties was also investigated.
12:45 PM - N5.11
Micro/Nanofabrication by Spin Dewetting on a Poly(dimethylsiloxane) Mold
Nicholas Ferrell 1 , Aimee Bross 2 , Derek Hansford 1 Show Abstract
1 Biomedical Engineering Department, Ohio State University, Columbus, Ohio, United States, 2 Nanoscale Patterning Laboratory, Ohio State University, Columbus, Ohio, United States
The ability to fabricate physically independent polymer micro and nanostructures is vitally important for applications ranging from microelectronics and MEMS to biomedical devices. Photolithography is the standard for fabrication of microstructures. The ability to fabricate polymer microfeatures from inexpensive, chemically versatile materials using more cost effective processing techniques is highly advantageous. Here we introduce the process of spin dewetting as a method for fabrication of polymer micro and nanostructures from various polymer materials. These microstructures can be used directly in device applications or as etch masks for further silicon processing. Polystyrene, poly(methyl methacrylate) (PMMA), and poly(n-propyl methacrylate) (PPMA) were used as the polymer materials in this work. The process involves spin coating of a polymer solution onto a micro or nanopatterned poly(dimethylsiloxane) (PDMS) mold. The topography of PDMS surface leads to a variety of interesting film morphologies. Three basic scenarios can result after spin coating. The polymer can completely dewet into the recessed features of the mold. The polymer can partially dewet, in which case physically separated regions of polymer fill the recessed and the raised features of the mold. The material can also create a continuous but topographically nonuniform film. In each case, the polymer materials can be transferred from the mold onto the substrate of interest using heat and pressure in a single or double stamping technique. By engineering the proper combination of surface topography, solvent, polymer solution concentration, and spin speed a wide range of geometrical features can be fabricated from a single PDMS mold. This experimental study looks at the effects of the original mold feature geometry and polymer solution concentration on the resultant micro and nanostructures. In addition, this process was used for silicon based fabrication by using the polymers as etch masks. Etch rates of the masking materials were characterized to determine the appropriate polymer for both wet and dry etching. This process provides a simple and cost effective method for fabrication of polymer micro and nanostructures from non-traditional materials for applications in polymer and silicon processing.
Thursday PM, April 12, 2007
Room 2003 (Moscone West)
2:30 PM - N6.1
Multi-Component Polymer Brushes
Zhou Feng 1 , Zijian Zheng 1 , Wilhelm T S Huck 1 Show Abstract
1 , Cambridge University, Cambridge United Kingdom
Polymer brushes have emerged as a robust method for creating surfaces with a wide range of mechanical and chemical properties and could in many ways act as ideal alternatives to self-assembled monolayers. The use of polymers as building blocks for surface modification introduces the possibility to make ‘smart’ or responsive surface based on conformational changes in the polymer backbones. Registration of a number of polymer brushes that sit next to each other on a single substrate can realize multiple functionalization, and multiply responsive properties. Such lateral multi-component polymeric surfaces could find use as model substrates for tissue engineering or biosensors or study on site selective issues, where very often a complex range of chemical functionalities in a well-defined spatial arrangement are required. Multiple responsive surfaces could also be used for guided flow in microfluidic devices and for tuning surface roughness at different lengthscales. We will report a simple approach to achieve lateral multi-component polymer brushes, which includes multiple micro contact printing (μCP) and surface initiated atomic transfer radical polymerization (SIP-ATRP). Specifically, the approach consists of topographic printing, i.e., delivery of initiator to the blank substrate on top of already-grafted brushes, the passivation step which kills the remaining initiator before growing next brushes, and backfilling initiator at last step for growing final brushes. Applications of these surfaces include flexible functionalization for versatile bioattachment and efficient templates for metallization and biomineralization. Surprisingly, these polymer brushes can build up nano-scale patterns by topographic effect during contact printing.
2:45 PM - N6.2
Immobilization of Multiple Proteins on Photosensitive Hydrogel Surface.
Parijat Bhatnagar 1 , Dickson Kirui 1 , George Malliaras 2 , Scott Blanchard 3 , Lawrence Bonassar 4 1 , Carl Batt 5 Show Abstract
1 Biomedical Engineering, Cornell University, Ithaca, New York, United States, 2 Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 3 Physiology, Biophysics and Systems Biology, Weill Medical College of Cornell University, New York, New York, United States, 4 Mechanical & Aerospace Engineering, Cornell University, New York, New York, United States, 5 Food Science, Cornell University, New York, New York, United States
A process for sequential patterning of multiple proteins on a hydrogel surface has been developed. A silicon substrate was derivatized with a self-assembled monolayer of [3-(Methacryloyloxy)propyl]trimethoxysilane that contains a polymerizable group. The cross-linked hydrogel copolymer (acrylamide – co – methylenebisacrylamide – co – o-nitrobenzyl methacrylate) film with carboxylic acid group on the side-chain protected by photolabile 2-nitrobenzyl ester was polymerized on the surface using free-radical polymerization. Projection photolithography was then used to photo-cleave 2-nitrobenzyl group to deprotect the acid groups in discreet regions on the hydrogel film. The proteins were finally coupled to these photo-generated acid groups through their primary amine groups using 1-Ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride and N-hydroxysuccinimide. The carboxylic acid groups on proteins were modified to hydroxyl groups and the process was repeated to sequentially pattern other proteins on the hydrogel surface. The resulting pattern of multiplexed proteins was confirmed using fluorescently labeled antibodies against the respective proteins and a minimum of three proteins were sequentially patterned.
3:00 PM - **N6.3
Self-organization of Colloidal Particles on the Surfaces of Emulsion Drops for Biomimetic Compound Eyes.
Seung-Man Yang 1 2 , Shin-Hyun Kim 1 , Chul-Joon Heo 1 , Su Yeon Lee 1 , Gi-Ra Yi 2 Show Abstract
1 National Creative Research Initiative Center for Integrated Optofluidic Systems, KAIST, Daejeon Korea (the Republic of), 2 Department of Chemical & Biomolecular Engineering, KAIST, Daejeon Korea (the Republic of)
3:30 PM - **N6.4
Fabrication of Molecular Micro-NanoStructures by Surface-Tension-Driven Technique
Giuseppe Gigli 1 Show Abstract
1 , national nanotechnology lab of cnr-infm, Lecce Italy
Fabrication of micro-nanostructures for opto-electronics and electronics is a challenging task motivated by the growing request of downscaling the device size and of pixel arrays integration. In this context, patterning molecular materials seems to be crucial in several application, such as integrated optical devices, full-colour displays, lighting panels or backlight systems, where resolution improvement requires an increase of pixel integration. Top down lithographies, such as Soft Embossing and Nano-imprinting, have find development for patterning organic compounds quite easily, with low cost and high resolution. Anyway these techniques do not easily allow to fabricate disconnected features without any relevant damages in the chemical properties of the material employed. To this aim bottom up technologies which exploit peculiar characteristics of molecular materials, such as self-assembling and recognition capabilities, seem to be much more suitable, allowing the formation of molecular structures by spontaneous aggregation in a constructive fashion and due to free energy minimization induced processes In this work molecular patterned layers were realized by a surface-tension-driven (STD) technique, by taking advantages of the combination of both liquid instabilities, following dewetting phenomena, and geometrical confinement, induced by external constrains. More importantly, the interplay of surface energies and liquid surface tensions allows the single-step realization of a multicolour pixel array starting just from a single active organic molecule.
4:30 PM - N6.5
Fabrication of Biomimetic Fluidic and Biosensor Structures by Directed Self-Assembly of Colloidal Silica Nanoparticles
Deying Xia 1 , Steve Brueck 1 Show Abstract
1 Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico, United States
4:45 PM - N6.6
Bioplume: A MEMS-based Femtoliter Droplet Dispenser with Electrospotting Means for Patterning Surfaces at the Micro-and Nanometer Scales.
Thierry Leïchlé 1 , Fabrice Mathieu 1 , Jean-Bernard Pourciel 1 , Daisuke Saya 1 , Christian Bergaud 1 , Nicu Liviu 1 Show Abstract
1 Nanobiotechnology Department, LAAS CNRS, Toulouse France
The need for patterning surfaces with organic or inorganic materials at a micro and nanometer scale is of crucial importance for designing novel hybrid devices with unconventional properties for photonics, electronics, biosensors, etc. Among various patterning methods, dispensing techniques relying on the use of microcantilevers are very promising for several reasons. The first one is that they permit a direct patterning of the surface with different kinds of materials without any need for prefabricated patterns. Secondly, alignment of the cantilevers with respect to specific regions on the surface is straightforward since the cantilevers themselves can be used as displacement sensors. Moreover, to overcome the serial nature of cantilever-based techniques, parallel approaches can be developed to meet specific requirements in terms of throughput and fabrication costs. Finally, electrically-assisted deposition can be envisaged provided that addressable electrodes are implemented onto the cantilevers.A fully automated MEMS designed for the trim control of a microspotting system (so called "Bioplume") using an integrated parallel force sensor with high precision and sensitivity will be presented. This microsystem improves the results, in terms of size and homogeneity of deposited droplets, through a direct-contact method. It allows the contact time and the force to be controlled during deposition. Using this method, homogeneous spots can be realized leading to a reproducible analysis. Proof-of-concept experiments have been carried out to demonstrate the versatility of our deposition system in terms of deposited materials and spot size ranging from the micro to nanometer scale. More specifically, we will discuss results obtained for surface patterning with oligonucleotides, proteins, molecular imprinted polymers, conductive polymers, nanoparticles, etc. through direct deposition with and without electrically-assisted techniques.
5:00 PM - N6.7
Patterning of Gold Nanoparticles by Dip-Pen Nanolithography.
Wechung Wang 1 , Zhenan Bao 1 Show Abstract
1 Chemical Engineering, Stanford University, Stanford, California, United States
The patterned assembly of metal nanoparticles has garnered much research interest due to their unique electrical and optical properties, as well as their potential applications in nanodevices for biosensing. A promising method for creating nanoscale patterns of gold nanoparticles is dip-pen nanolithography. This technique uses a scanning probe to deposit inks such as small molecules, polymers and nanoparticles on various substrates with nanoscale resolution. Our study focuses on the direct writing of gold nanoparticles via electrostatic interactions with modified silicon oxide substrates. Adequate inking of cantilever tips was found to be crucial for reproducible nanoparticle deposition. Different inking protocols were tested, and inked tips were subsequently imaged by scanning electron microscopy to determine ink coverage and gain insight into the deposition process. Writing speeds and patterns were optimized to obtain uniform structures. Resultant gold nanoparticle patterns were characterized by atomic force microscopy. Applications of these nanoparticle patterns are discussed.
5:15 PM - N6.8
Biomemetic Antireflective Coatings
Peng Jiang 1 Show Abstract
1 Chemical Engineering, University of Florida, Gainesville, Florida, United States
Part of the light incident on all transparent materials is reflected. This reflection arises from the abrupt change in the refractive index at the interface of two media. The cornea of some nocturnal moths has a structure with a repeating pattern of less than 250 nm and a physical depth of less than 200 nm. These submicrostructured surfaces can greatly reduce reflection, helping conceal the inset from hungry predators. Here we report a simple bio-inspired self-assembly technique for fabricating artificial moth-eye antireflective coatings. Non-close-packed colloidal crystals with remarkable large hexagonal domains are created by a spin-coating technology, which is based on shear-aligning colloidal silica particles suspended in non-volatile triacrylate monomers. The resulting polymer-embedded colloidal crystals exhibit highly ordered surface modulation and can be used directly as templates to cast poly(dimethylsiloxane) (PDMS) molds. Polymer (e.g., PMMA and polystyrene) and glass antireflective coatings can then be molded against PDMS using traditional polymerization and sol-gel technologies. The depth of the micropatterns can be adjusted by plasma-etching of the original colloidal crystal-polymer nanocomposite. Using the above colloidal self-assembly and micromolding techniques, large-area (up to 8-inch diameter, limited only by the substrate size) moth-eye antireflective coatings have been created on both planar and curved substrates. The microstructured coatings exhibit much lower reflectivity than bare films and the optical reflection matches with the theoretical prediction using effective medium theory.
5:30 PM - N6.9
Unique Tools for Multi-Pen and Multi-Ink Patterning by Dip Pen Nanolithography® (DPN®)
Emma Tevaarwerk 1 , Jason Haaheim 1 Show Abstract
1 , NanoInk, Inc, Skokie, Illinois, United States
Precision nanoscale deposition of biological, organic, and inorganic materials is a fundamental need in nanoscience research. Relative to other nanopatterning techniques, Dip Pen Nanolithography® (DPN®) is a direct-write technique maintaining high resolution (14 nm line widths, 20 nm pitches), and among sub-50 nm techniques, DPN is the only one that can directly deposit molecules under ambient conditions; this enables deposition of a wide variety of biological, organic and inorganic materials. Until recently DPN remained a relative serial technique, typically with the deposition of only a single ink. Herein we present data demonstrating advances in NanoInk’s DPN nanopatterning tools made for large area and multi-ink patterning. We demonstrate results of DPN pattering with one dimensional and two-dimensional probe arrays, Active Pen™ individually actuated cantilevers, and microfluidic ink delivery tools. We discuss the implications of these results and tools in furthering the application of DPN as a large scale, multiplexed patterning tool.
N7: Poster Session: Printing Methods for Electronics, Photonics, and Biomaterials
Friday AM, April 13, 2007
Salon Level (Marriott)
9:00 PM - N7.1
Rubber-stamp-printed Pentacene Organic Field-effect Transistor on a Glass Substrate with High Mobility.
Jin-Woo Han 1 , Young-Hwan Kim 1 , Byung-Yong Kim 1 , Jong-Yeon Kim 1 , Dong-Hun Kang 1 , Dae-Shik Seo 1 Show Abstract
1 electrical and electronic engineering, Yonsei university, Seoul Korea (the Republic of)
9:00 PM - N7.10
Micro-well Arrays and Patterned Gold Filmsby Colloidal Assisted Soft Lithography
Hye Jin Nam 1 , JuYeon Chang 1 , Geun-Tae Cho 1 , Duk-Young Jung 1 Show Abstract
1 Chemistry, SungKyunKwan University, Suwon, Kynuggi-do, Korea (the Republic of)
We report a simple and effective technique for fabricating micro-well arrays with close-packed honeycomb patterns on solid surfaces by using ordered polystyrene (PS) microspheres. Two types of micropatterned polymer films were prepared by colloidal particle-assisted soft-lithographic technique. One is elastomeric polydimethylsiloxane (PDMS) mold with ordered hexagonal array of sub-micrometer sized wells fabricated by casting PDMS prepolymer against colloidal PS crystal template. We prepared patterned applied micro-contact printing to produce hexagonal micropatterns of gold nanoparticles by dip-coating the printed substrates in the Au solution. The second is polymer-polymer composite films of PS-PDMS with ordered hexagonal arrays, which directly formed after removal of PDMS mold. Highly ordered three-dimensional gold-polymer microstructures were formed by curing of the PDMS prepolymer infiltrated into the void spaces among polymeric microspheres, followed by deposition of gold thin layers on the polymer layers. The thermal treatment of the gold-polymer composite films produces three dimensional micro-well arrays and embossed surface of gold thin layers on the solid substrates. This technique provides a useful method to be readily extended to make 3D structures of the wide range of materials.
9:00 PM - N7.11
Au Nanoparticle Fluids: Corona Chemistry and Properties.
Robert MacCuspie 1 2 , Steve Diamanti 1 2 , Richard Vaia 1 Show Abstract
1 MLBP, Air Force Research Lab, Wright-Patterson AFB, Ohio, United States, 2 , National Research Council, Washington, District of Columbia, United States
A methodology that maximizes nanoparticle volume fraction (>40%) while enabling visco-elastic molar Newtonian flow of collective assembly would provide novel materials with applications in areas as diverse as conductive lubricants, actuators, compliant electrodes, and direct surface patterning of materials without the requirement of masking techniques. These so-called “Nanoparticle Fluids” are contingent upon minimizing the relative volume of surface passivation to yield an effective hard-core repulsive potential between particles.To achieve a greater understanding of the potential of nanoparticle fluids as functional nanomaterials, the corona chemistry of gold nanoparticles and gold nanoparticle fluids will be studied systematically by varying: 1)alkylthiol ligands on the gold nanoparticle surface that contain a negatively charged functional group, such as sulfates, carboxylic acids, alcohols, and uncharged alkanes; 2)the alkyl chain length between the thiol and the negatively-charged functional group, for example 16-mercaptohexadecanoic acid and 3-mercaptoproprionic acid; 3)citrate-thiol mixed monolayer protected clusters against pure thiol monolayer protected clusters; 4)the positive counter-ion in the canopy, for example linear vs. branched chain alkyl quaternary ammonium salts. Systematic study of the corona and canopy chemistry of nanoparticle fluids will be performed to determine the effects on physical properties such as conductivity, viscosity and surface tension. Understanding of the relationship between these properties and the underlying chemistry will allow determination of the suitability of various nanoparticle fluids for various applications, for example conductive lubricants capable of extending the functional life cycle of RF MEMS devices by over 5 orders of magnitude.
9:00 PM - N7.12
Novel Elastomeric Ink for Direct Writing of 3D Micro-Periodic Structures
Robert Barry 1 , Robert Shepherd 1 , Pierre Wiltzius 1 , Jennifer Lewis 1 Show Abstract
1 Materials Science, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Methods to design periodic structures on the micron scale are of interest for photonics and other applications. We have developed a new material system that can be robotically patterned in the form of 3D micro-periodic lattices. This gel-based ink has elastomeric properties, which are retained after initial setting. Alternately, after patterning, this ink can be transformed into a rigid material. This processing flexibility enables these complex 3D structures to be used in a variety of potential applications; including photonics, filters, sensors and more. It can be employed directly, in either elastomeric or rigid forms, or it could be used as a scaffold to guide the assembly of other materials.
9:00 PM - N7.13
Focused Assembly of Nanoparticles Using Localized Fringing Fields.
Chad Barry 1 , Stephen Campbell 1 , Uwe Kortshagen 2 , Heiko Jacobs 1 Show Abstract
1 Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, United States, 2 Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, United States
We report on a new gas phase printing approach to deposit nanomaterials into addressable areas on a surface with 50 nm lateral accuracy. Localized fringing fields that form around conventional resist patterns (PMMA and SiO2) with openings to a silicon substrate are used to direct the assembly of nanomaterials into the openings. Directed assembly was observed due to a naturally occurring inbuilt charge differential at the material interface which was further enhanced by corona charging to yield a field strength exceeding 1 MV/m in Kelvin Probe Force Microscopy (KFM) measurements. The assembly process is independent of the nanomaterial source and type – an evaporative, plasma, and electrospray source have been tested to deposit silicon and metallic nanoparticles. The results suggest a potential route to form nanolenses on the basis of charged resist structures – a 3 fold size reduction has been observed between the structures and the assembled particles. Applications range from the integration of functional nanomaterial building blocks to the elimination of lift-off steps in semiconductor processing.
9:00 PM - N7.14
Prediction of Deposit Morphologies from the Deposition and Coalescence of Ink Jet Printed Droplets.
Jonathan Stringer 1 , Brian Derby 1 Show Abstract
1 School of Materials, University of Manchester, Manchester United Kingdom
Ink jet printing of material-laden droplets is an additive fabrication technique with potential applications in fields such as biomaterials, flexible electronics and MEMS. To fully realise the potential of ink jet printing, it is necessary to understand how a series of individual droplets deform, coalesce and change phase upon impact with a substrate. An understanding of these processes determines the size and spacing achievable, enabling faster and more accurate design of ink jet printed structures.The footprint of an individual droplet on a substrate is determined by the size of droplet and the surface energy interactions between the droplet and substrate. Due to pinning of the contact line, this diameter is also found to accurately predict the size of deposit left after evaporation of the carrier solvent. The coalescence of adjacent droplets can lead to three different morphologies: a stable bead with parallel contact lines, a series of bulges connected by ridges and a bead exhibiting a contact line with a periodic ‘waviness’. The occurrence of the different morphologies is dependent upon droplet size, droplet spacing, surface energy interactions and the prevalence of a pressure-driven axial flow within the bead.By modelling the bead formed from a series of adjacent droplets, the width of a stable bead can be predicted, with good agreement found between the model and both a solution and suspension deposited on substrates with differing surface energies. A threshold is al