Dawen Li The University of Alabama
Graciela Blanchet Nano Terra, Inc.
Takao Someya The University of Tokyo
Bruce Gnade University of Texas-Dallas
Xing Cheng Texas A&M University
T2: Contact and Transfer Printing
Tuesday PM, April 26, 2011
Room 3007 (Moscone West)
2:30 PM - **T2.1
Large Area, Three Dimensional Metamaterials by Printing.
John Rogers 1 Show Abstract
1 , University of Illinois, Urbana, Illinois, United States
Recent work shows that solid materials can be printed in additive or subtractive modes, to yield classes of two and three dimensional (3D) micro/nanostructures that would be impossible to achieve using other methods. This talk describes materials and printing techniques designed to achieve large area 3D plasmonic and negative index metamaterials, on both rigid and flexible substrates. Systematic studies of the materials science and optics of printed, cavity-coupled plasmonic crystals and multilayer fishnet type structures illustrate the capabilities of these approaches, and foundational aspects of the underlying processes.
3:00 PM - **T2.2
Materials for High-Performance Printed Transistors.
Antonio Facchetti 1 2 Show Abstract
1 Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois, United States, 2 , Polyera Corporation, Skokie, Illinois, United States
In this presentation we discuss the synthetic and fabrication strategies to new organic, inorganic, and hybrid materials for printed transistors. Particularly the synthesis of new high-mobility electron-transporting organic semiconductors based on the naphthalene diimide core will be presented. These n-channel materials are combined with new p-channel semiconductors to fabricate printed CMOS devices. Furthermore, we will present new results demonstrating the large thermal, chemical, and bias-stress stability of n-channel materials. Finally, a new type a gate dielectric combining facile fabrication and high stability will be discussed.
3:30 PM - T2.3
Use of Supercritical Fluids to Enhance the Mechanical Stability of Silica/Carbon Structures Micromolded on Silicon for Electrochemical Sensing Applications.
Marti Gich 1 , Muhammad Hamza Ikram 2 , Cesar Fernandez-Sanchez 3 , Andreu Llobera 3 , Esther Carregal 3 , Anna Roig 1 Show Abstract
1 , Institut de Ciencia de Materials de Barcelona CSIC, Bellaterra Spain, 2 , Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi Pakistan, 3 , Institut de Microelectrònica de Barcelona, CNM-IMB-CSIC, Bellaterra Spain
The combination of soft lithography with silicon sol-gel technologies constitutes a versatile, cost-effective and high-throughput microfabrication process . However, the mechanical stresses provoked by the shrinkage of sol-gel microstructures upon drying is one of the major drawbacks of the technique, imposing limitations to the use of certain precursors and to the dimensions and geometries that can be imprinted. Here we will show how pattern collapse, caused by the capillary forces occurring during gel drying, can be avoided if the structure is dried in supercritical fluid conditions. The interest of this technology will be illustrated with the preparation of micromolded silica/carbon structures intended for the implementation of electrodes in electrochemical sensors. In particular, we will show that the drying of hybrid organic-inorganic gel microstructures obtained by the MIMIC technique under supercritical CO2 results in an improved mechanical stability of the silica/carbon structures obtained after pyrolysis.  C. Fernández-Sánchez et al. Chem. Mater. 20 (2008) 2262.
3:45 PM - T2.4
Patterning Biopolymer Surfaces by Enzymatic Soft Lithography.
Aurelie Guyomard-Lack 1 , Celine Moreau 1 , Nicolas Delorme 2 , Jean-Francois Bardeau 2 , Bernard Cathala 1 Show Abstract
1 UR 1268, Biopolymères, Interactions et Assemblages, INRA, Nantes France, 2 Laboratoire de Physique de l'Etat Condensé, UMR CNRS 6087, Institut de Recherche en Ingénierie Moléculaire et Matériaux Fonctionnels (FR2575), Université du Maine , Le Mans France
Surfaces patterned with micro- and nano-scale functional polymers or molecules that offer various physicochemical properties are attracting considerable interest1 for their potential applications in cell or tissue engineering2, biomimetic approaches3 or fundamental surface science research4. Soft lithography which includes microcontact printing (μCP) can be applied to a wide variety of substrates5. μCP is simple enough to be used in a typical laboratory setting and does not require prohibitively expensive equipment. Since its initial development, μCP has undergone spectacular improvement of its capability to form SAM patterns of various polar, apolar materials and biomolecules over macroscopic areas5 and can also be used for selective patterning of a surface when reactive species are used as “ink”. The use of μCP combined with enzymes offers a low cost and versatile method for site-selective chemical surface patterning with high resolution. The method reported here is based on the deposition of a biopolymer layer on a surface and hydrolysis of the layer by microcontact printing with immobilized hydrolytic enzyme as ink. Covalent attachment together with the exquisite selective degradation of enzyme provides both well define pattern and leads to versatile strategies for masking/unmasking the surface to undergo selective modification. We report here the principles of the method and possible applications of the patterned surfaces. First, we focus on the specific functionalization of surfaces subjected to enzymatic lithography by an amino-silane. The second example illustrates selective polymer adsorption and offers an original strategy for patterning a polyelectrolyte multilayer. The third one shows the pattern-driven adsorption of hydrogel beads. As in both cases, efficient modifications of the surface have been obtained by rapid, cheap and easy-to-use processes, we demonstrate that this method can serve as ideal tools for producing large scale patterns of biological materials for potential biological and physical applications. (1) Nie, Z. H.; Kumacheva, E. Nature Materials 2008, 7, 277-290.(2) Théry, M.; Racine, V.; Piel, M.; Pépin, A.; Dimitrov, A.; Chen, Y.; Sibarita, J.-B.; Bornens, M. Proceedings of the National Academy of Sciences 2006, 103, 19771-19776.(3) Huebsch, N.; Mooney, D. J. Nature 2009, 462, 426-432.(4) Seemann, R.; Brinkmann, M.; Kramer, E. J.; Lange, F. F.; Lipowsky, R. Proceedings of the National Academy of Sciences of the United States of America 2005, 102, 1848-1852.(5) Perl, A.; Reinhoudt, D. N.; Huskens, J. Advanced Materials 2009, 21, 2257-2268.
4:30 PM - T2.5
Gravure Printed Polymer Field-Effect Transistors.
Alasdair Campbell 1 , Monika Voigt 1 , Alex Guite 1 , Dae-Young Chung 1 , Fanshun Meng 1 , Joachim Steinke 1 , Donal Bradley 1 Show Abstract
1 Physics, Imperial College London, London United Kingdom
Gravure contact printing is the highest volume printing technique known. Here we report in detail the gravure printing of polymer field-effect transistors (PFETs) on flexible substrates. We used pre-patterned ITO source and drain contacts, as common for ink-jet printed devices. We then gravure printed four different layers consisting of the semiconductor poly(3-hexylthiophene-2,5-diyl) (P3HT), two insulator layers and a metal ink gate layer. Printing in ambient and using this bottom contact / top gate geometry we can achieve an on/off ratio of > 104 and mobility of 0.04 cm^2/Vs. This rivals the best top gate polymer PFETs fabricated with these materials. The printing speed of 40 metres/minute on a flexible polymer substrate demonstrates that very high-volume, reel-to-reel production of organic transistors is possible.
4:45 PM - T2.6
Transfer-printed Metal Electrodes for Thin Film Nanocrystal Devices.
Sarah Swisher 1 4 , Jessy Baker Rivest 2 4 , A. Paul Alivisatos 3 4 Show Abstract
1 Department of Electrical Engineering, University of California Berkeley, Berkeley, California, United States, 4 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Department of Mechanical Engineering, University of California Berkeley, Berkeley, California, United States, 3 Department of Chemistry, University of California Berkeley, Berkeley, California, United States
Many novel thin film device architectures would benefit from a reproducible method of depositing metal electrodes using a non-damaging technique that is compatible with low-temperature processing requirements. Thermal evaporation of metal electrodes onto thin films of semiconductor nanocrystals can result in damage to the crystal surfaces, diffusion of the metal into the nanocrystal, and shorting of the device through pin-holes in the nanocrystal film. We present an alternative method for electrically contacting semiconductor nanocrystal thin films using elastomeric stamps, where transfer of the metal to the substrate does not require an interfacial adhesion layer. We have demonstrated the usefulness of this contact method using a well-studied system of lead chalcogenide quantum dots. The elastomeric stamp contact deposition method not only allows reproducible contacts to materials prone to pin-holes, but also enables thinner layers of active material, which could benefit thin film solar cells that suffer from a short carrier mean free path.
5:00 PM - T2.7
Nanowire-based, Macroscale Artificial Skin Sensor with Low Voltage Operation.
Kuniharu Takei 1 , Toshitake Takahashi 1 , Andrew Gillies 1 , Ronald Fearing 1 , Ali Javey 1 Show Abstract
1 EECS, University of California, Berkeley, Berkeley, California, United States
High performance macro scale flexible electronics are of interest for wearable human interface applications. Recently, there has been significant progress in the use of using both organic and inorganic materials for flexible applications. However, for practical wearable electronics, demonstration of both macro-scale, flexible electronics and low voltage operation is still required. To address this challenge, we demonstrate a macroscale (7×7 cm2) artificial skin sensor array (18×19 pixels) using our developed inorganic semiconductor nanowire (NW) contact printing method as an active macroscale flexible platform1,2. The integrated sensor array enables to monitor applied pressure distributions with high sensitivity (~11.5 μS/kPa) as an artificial electronic skin at a low operating voltage <5 V for active matrix circuitry. The device shows remarkable mechanical robustness and reliability with no performance degradation for bending down to small radii of curvature (2.5mm) for over 2000 bending cycles. This work presents the largest integration of ordered nanowire active components for a functional system. The artificial skin sensor is just one of examples to prove our macroscale flexible platform, and this platform would be applied to further advanced nano material electronics such as practical wearable electronics for the future. Reference Z. Fan et al, Advanced Materials 21, 648-653, 2009. K. Takei et al. Nature Materials 9, 821-826, 2010.
5:15 PM - T2.8
Parallel Array InAs Nanowire Transistors for Flexible Ultrahigh Frequency Electronics.
Toshitake Takahashi 1 , Kuniharu Takei 1 , Ehsan Adabi 1 , Ali Niknejad 1 , Ali Javey 1 Show Abstract
1 Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, California, United States
In recent years, semiconductor nanowires (NWs) have been intensively studied as potential applications such as electronics and sensors due to their unique electrical and optical properties. As the generic approach for large-scale integration of NWs, contact printing method has been explored, in which as-grown NWs are directly transferred on virtually any substrate such as paper and plastic1. In this report, as one of such examples, chemically synthesized InAs NWs are printed on mechanically flexible substrate and its radio frequency response is characterized. Despite the relatively long channel length of 1.5 microns, the parallel array of InAs NWs exhibits GHz performance. This work opens up a new platform for cost-effective, flexible ultrahigh frequency devices for high frequency digital and analog circuitry.1. Zhiyong Fan et al., Advanced Materials 2009, 21, 3730-3743.2. Toshitake Takahashi et al., ACS Nano 2010, 4, 5855-5860.
5:30 PM - T2.9
Two-step Transfer Printing of Metal Nano-inks for Printed Flexible Electronics Fabrication.
Sanghyuk Kim 1 2 , Inkyu Park 1 2 Show Abstract
1 Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejon Korea (the Republic of), 2 KAIST Institute for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejon Korea (the Republic of)
Conventional metallization methods based on vacuum processes are widely used for the fabrication of micro/nano-scale electrodes and interconnections. These technologies have been well-established and therefore can achieve high film quality. However, they require high manufacturing cost, stringent environment control, and multiple steps such as deposition, etching, lift-off, etc. For these reasons, there are growing interests about printing-based direct metal patterning methods. Screen printing, gravure, offset, flexography, inkjet printing, and nanoimprinting are a few representative processes. These methods have many advantages such as low manufacturing cost, simple fabrication process, and compatibility with various substrates. In the present work, we present a new direct metal patterning method by two-step transfer printing process of conductive metal nano-ink solution. The fabrication procedures are as follows: First, a silver nano-ink solution was spin-coated on the donor substrate. Then, a polydimethylsiloxane (PDMS) stamp with a variety of microscale patterns was pressed onto the donor substrate in the 1st transfer (T#1) process step. Afterwards, PDMS stamp covered with silver ink was pressed onto the target substrate in the 2nd transfer (T#2) process. Finally, the metal patterns printed on the target substrate were annealed at 140degC in order to remove solvent and form continuous and conductive silver structures by coagulation and sintering of silver nanoparticles.Various materials including silicon wafer and flexible polymer film (polyimide and polyethylene terephthalate) were used as target substrates. Furthermore, a silicon substrate with uneven surface morphology (pattern depth=10μm) and curved glass substrate were also used as target substrates. Uniform and clean metal patterning could be achieved on these various substrates. Pressure, temperature, and contact period were controlled at various conditions as process parameter during the T#1 and T#2 steps. In addition to these parameters, the stiffness of the stamp exhibited an influence on the quality of the patterning. Therefore, h-PDMS (‘hard’ PDMS) stamp was used in the experiment for more uniform and precise contact with target substrate and less deformation of patterns during the contact period. In addition to monolayer patterns, bilayer patterns of line array were achieved. After the patterning of the first layer and thermal sintering, the second layer was aligned and replicated on the first layer pattern. Two-step transfer printing process is very simple but provides high resolution metal patterning. Further, the low temperature and pressure process conditions allow compatibility with various substrates. Therefore, it is believed that this method will provide a convenient and reliable route to the printed electronics manufacturing technology.
5:45 PM - T2.10
Gravure Contact Printing of Flexible, High-performance Polymer Light Emitting Diodes for Large-area Displays and Lighting.
Alasdair Campbell 1 , Dae-Young Chung 1 , Jingsong Huang 1 , Dong-Seok Leem 1 , Donal Bradley 1 Show Abstract
1 Physics, Imperial College London, London United Kingdom
Gravure contact printing is the ultra-high volume printing method, conventionally used to fabricate newspapers, magazines, postage stamps and currency, at speeds of up to 60 square meters per second. The ability to fabricate large area organic electronic devices using this method will revolutionize consumer electronics, producing a whole range of radically new, lightweight and flexible products.Conventionally processed polymer light emitting diodes (PLEDs) consist of an Indium Tin Oxide (ITO) anode, a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole injection layer, the light emitting polymer (LEP) layer, a Ca top cathode under an Al capping layer. We were able to print PEDOT:PSS by adding low boiling point, low surface tension solvents and a surfactant to the as received water-based formulation. The polyfluorene-based LEP was printed from a blend of xylene and cyclohexane. The resultant polymer light emitting diodes had a performance equal to that of fully spin-coated control devices. In addition we are able to gravure print the inorganic cesium carbonate electron injection layer (EIL) in multilayer inverted PLEDs. The performance of the LED with the printed EIL on top of amorphous ITO on plastic substrates exceeded that of spin-coated EIL control devices.We discuss the printing of these layers in terms of substrate wetting envelopes, lateral Marangoni forces, capillary flow and coffee ring effects, surface cooling, viscosity, polymer surface gel formation, and the threshold for the onset of Bénard-Marangoni and Rayleigh-Bénard instabilities.Finally we review the status of gravure printed PLEDs. The appearance of gravure printable ITO and metal ink nanoparticles shows that we have now have all the components we need to fabricate fully-printed large-area PLED based lighting and displays.
Dawen Li The University of Alabama
Graciela Blanchet Nano Terra, Inc.
Takao Someya The University of Tokyo
Bruce Gnade University of Texas-Dallas
Xing Cheng Texas A&M University
T4: Solution Processing and Flexible Substrates
Wednesday PM, April 27, 2011
Room 3007 (Moscone West)
2:30 PM - **T4.1
Controlling Organic Semiconductor Growth and Crystalline Orientation during Solution Processing.
Zhenan Bao 1 Show Abstract
1 , Stanford University, Stanford, California, United States
Organic semiconductor materials are interesting alternatives to inorganic semiconductors in applications where low cost, flexible or transparent substrates, and large area format is required. Currently they have been incorporated into organic thin-film transistors (OTFT), integrated display driver circuits, photovoltaics and radio frequency identification tags. In this talk, I will present recent results on material design, surface and interface control for achieving efficient charge carrier transport and large area patterning of organic semiconductors using solution processing.
3:00 PM - **T4.2
Materials and Device Integration for Printed Large Area Applications.
Tse Nga Ng 1 , Beverly Russo 1 , Brent Krusor 1 , Jurgen Daniel 1 , Ana Arias 1 Show Abstract
1 , Palo Alto Research Center, Palo Alto, California, United States
Solution-processed electronic materials have the potential to create a new manufacturing paradigm and applications domains beyond those now dominated by silicon technology. These materials can be deposited and patterned with tools commonly used in the graphics design and printing businesses. Over the past 10 years, solution-processed semiconducting materials have been studied largely for incremental application in information displays. However, combining derivatives of these semiconductors with emerging solution-dispersible metal and metal oxide nanoparticles and nanowires enables the fabrication of electronic devices that are fully built from solution. This establishes a new device processing platform which, in turn allows device form factors and integration of functionality in systems not feasible in any conventional semiconductor technology. Examples of novel applications and systems enabled by this include: large-area, ultralight and flexible power harvesting, logic-integrated sensing and memory technologies. In this talk, I will discuss the development integrated sensing systems to illustrate and demonstrate the challenges and advantages of using solution-processed electronic materials for flexible applications. The electronic circuits are based on digitally-printed organic semiconductors and integrated with pressure, acoustic, acceleration and temperature sensors based on piezoelectric polymers such as PVDF or PVDF-TrFE. Piezoelectric polymers were chosen based on their ability to meet low-power, low drift and simple fabrication constraints and in some cases provide the power needed in the system. Polarizable solution-processed dielectrics and polymer semiconductors were integrated in the fabrication of non-volatile analog memory arrays. In this talk I will also discuss the main challenges for flexible printed electronics: materials performance, TFT operation voltage, and printing as a manufacturing technology.
3:30 PM - **T4.3
Conducting Polymer Devices for Biosensors and Bioelectronics.
George Malliaras 1 Show Abstract
1 Centre Microelectronique de Provence, Ecole Nationale Superieure des Mines de St. Etienne, Gradanne France
Conducting polymer electrodes and transistors are being extensively studied for applications in biosensors and bioelectronics. The active conducting polymer layer can be deposited using solution or vapor-phase techniques, while the deposition on metal and insulator layers are also necessary to complete these devices. We will review a few examples of device architectures used to sense ions, metabolites such as glucose, and pathogens. We will then discuss their fabrication and compare the performance of devices fabricated using different techniques, including ink-jet printing and photolithography.
4:30 PM - T4.4
Improvement of Electrical Characteristics of Low Temperature Solution-processed Zinc Tin Oxide Thin Film Transistors by O2 Plasma Treatment.
Jeong-Soo Lee 1 , Yong-Jin Kim 1 , Yong-Uk Lee 1 , Seung-Hwan Cho 1 , Yong-Hoon Kim 3 , Jang-Yeon Kwon 2 , Min-Koo Han 1 Show Abstract
1 School of Electrical Engineering and Computer Sciences, Seoul National Universuty, Seoul Korea (the Republic of), 3 Flexible Display Research Center, Korea Electronics Technology Institute, Gyeonggi Korea (the Republic of), 2 Department of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Recently, solution-processed oxide thin film transistors(TFTs) have attracted considerable attentions because of its high mobility, low cost fabrication, high throughput, and large area process. In solution-processed Zinc Tin Oxide (ZTO) TFTs, high annealing temperature exceeding 500 °C is required in order to obtain low threshold voltage and high mobility, so that reduction of annealing temperature less than 500 °C in solution-processed ZTO TFTs would be a critical issue for additional cost reduction as well as employing flexible substrates.The purpose of this paper is to report that the electrical characteristics such as threshold voltage and saturation mobility of low annealing temperature solution-processed ZTO TFTs could be considerably improved by employing O2 plasma treatment on ZTO active layer.O2 plasma treatment causes preferential dissociation of weak bonding such as halide related bonding and simultaneous composition of O-related bonding of ZTO films by ion bombardment of energetic O2 plasma and this was investigated by Auger Electron Spectroscopy (AES). The atomic concentration of O was gradually increased from 52.93 % to 55.60 % and that of Cl was rather decreased from 0.69 % to 0.43 %, at from solution-processed ZTO films without plasma treatment to 300 W of plasma treatment.These changes of bonding cause the increase of electron concentration of ZTO films as Hall measurement results that the electron concentration of ZTO film without O2 plasma treatment was 6.55 X 1016 /cm3 and gradually increased to 4.04 X 1017 /cm3 by O2 plasma power of 300 W. The increase of electron concentration of ZTO films according to O2 plasma could be explained by the decrease of binding energy of ZTO films from OH-Cl bonding to Zn-O and Sn-O bonding. When binding energy decreases, the oxygen vacancies generate electron more easily so electron concentration of ZTO film increases.Moreover, the changes of bonding cause the reduction of halide residues in ZTO films considered as trap states acting as obstacles for electron accumulation and transportation of electron in the conduction band, and consequently reducing the mobility.Solution-processed ZTO TFT with channel length of 10 μm and width of 100 μm without plasma treatment exhibits threshold voltage of larger than 35 V and saturation mobility of 0.09 cm2/V–sec. By 300 W of O2 plasma treatment, TFT exhibits improved threshold voltage of 20.74 V and saturation mobility of 0.58 cm2/V–sec. The improvement of threshold voltage and saturation mobility by O2 plasma treatment is caused by the increase of electron concentration and the decrease of trap states, respectively. Therefore we could improve the electrical characteristics of ZTO TFTs to decrease threshold voltage and enhance mobility at low annealing temperature of 350 °C for ZTO active layer by employing O2 plasma treatment.
4:45 PM - T4.5
Photolitography-based CdS Thin Film Transistors for Flexible Electronics.
Ana Salas-Villasenor 1 , Israel Mejia 1 , Amanda Carrillo-Castillo 1 , Bruce Gnade 1 , Manuel Quevedo-Lopez 1 Show Abstract
1 Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas, United States
The authors demonstrate a photolithography-based thin-film transistor (TFT) with cadmium sulfide (CdS) semiconductor thin films as n-channel active layer. The CdS was deposited using chemical bath deposition (CBD) methods. The objective of this work is to develop a novel method to fabricate TFTs where the active semiconductor layer (CdS) is deposited at low temperatures using a low cost CBD method. Recently, CBD-deposited CdS has showed TFTs mobilities ranging from 0.25 to 1.5 cm2/V-s, which are comparable to those of a-Si TFTs (1-7). However, these reports are normally for simple processing including shadow mask and back-gated devices and no report shows a full photolithography-based process. The TFTs reported here were fabricated using photolithography-based processing and temperatures <100oC with four mask levels. In addition to improving the crystallinity of CdS film, an annealing step in Forming Gas atmosphere at 150oC for 1 hour was required for to form Ohmic contacts. Typical thickness of the CdS thin film was about 500 Å, measured by using a DM09 Veeco Atomic Force Microscope. Characteristics of the present CdS-TFTs were measured with a Keithley 4200 semiconductor analyzer. The drain voltage swept from 0 to 20 V at various gate voltages. All of the depositions were performed by chemical bath deposition for channel materials, thermal evaporation for metal contacts and thus the technology is directly applicable to large area and low temperature processing suitable for flexible microelectronics applications. Result shows an average mobility values in the order of 7 cm2/V-s for aluminum (Al) source and drain contacts. This high mobility is among the highest values reported for CdS TFTs chemically bath deposited and is attributed to the better interface formed between the dielectric and the CdS semiconductor layer after the annealing step. Ion/Ioff ratios of about ~107 were demonstrated.References1.J. S. Meth, S. G. Zane, K. G. Sharp, S. Agrawal, Thin Solid Films, 444, 227 (2003)2.J. H. Lee, J. W. Yoon, I. G. Kim, J. S. Oh, H. J. Nam, D. Y. Jung, Thin Solid Films, 516, 6492 (2008)3.C. Voss, S. Subramanian and C.-H. Chang, J. Appl. Phys. 96 5819 (2004).4.F.Y. Gan and I. Shih, IEEE Trans. Electron Devices 49 15 (2002). 5.J. S. Meth, S. G. Zane, G. Nunes, Appl. Phys. Lett., 84(15), 2922 (2004) 6.A.L. Salas-Villasenor, I. Mejia, J. Hovarth, H. N. Alshareef, D. K. Cha, R. Ramirez-Bon, B. E. Gnade, M. A. Quevedo-Lopez, Electrochem. Solid-State Lett., 13(9), H313, (2010).7.Y.-J. Chang, C.L. Munsee, G.S. Herman, J.F. Wager, P. Mugdur, D.-H. Lee and C.-H. Chang, Surf. Interface Anal. 37 398 (2005).
5:00 PM - T4.6
High-speed Solution-deposited Photovoltaics.
Heather Platt 1 , Susan Habas 1 , Maikel van Hest 1 , Calvin Curtis 1 , Alex Miedaner 1 , David Ginley 1 Show Abstract
1 , National Renewable Energy Lab, Golden, Colorado, United States
Rapid deposition of functional and electrically active thin films and patterns can be accomplished by a variety of methods, but not all of them are viable for large-scale manufacturing. Solution-based techniques such as spray pyrolysis and aerosol or ink jet printing provide high material utilization and non-contact alternatives to the more commonly utilized screen printing and vacuum-based methods. These large-area ink deposition tools have been incorporated into the Atmospheric Processing Platform (APP) at NREL, along with complementary rapid thermal processing and characterization equipment. The APP provides an inert environment in which 156 mm x 156 mm wafers and substrates can be placed to deposit absorbers, transparent conductors, and metal lines. One application of particular interest is the investigation of low-cost metal-organic decomposition inks to form Al, Cu, or Ni features on heated substrates. We have previously reported aerosol jetted sub-50 μm wide lines with respectably low resistivities of 11 μΩ-cm for Cu (~ 6 times bulk) and 17 μΩ-cm for Ni (~ 2 times bulk), and the APP has also enabled us to modify the ink chemistry to successfully deposit Al lines. These results will be discussed, along with examples of solution-deposited absorbers, to demonstrate the APP’s capacity to contribute to the fabrication of large-area photovoltaic devices.
5:15 PM - T4.7
Real Time Observation of Phase Separation in Spin Coated Polymer Blends using Stroboscopic Interference Microscopy.
Jonathan Howse 1 , Stephen Ebbens 1 Show Abstract
1 Chemical Engineering, Sheffield University, Sheffield United Kingdom
Spin coating is commonly used to make thin films of high uniformity over large surface areas. As a research tool it is widely used to make component layers in conductive polymers systems for light emitting diodes as well as polymer based photovoltaics. The final performance of such devices depends greatly upon the morphology of the film, in particular the interface between components. When blends of polymers are spun from a single solution a rich variety of phase separated morphologies results which affect the device performance. Control over this process, determined from a better understanding of this process therefore allows for significant device improvements to be realised. However, spin coating by its very nature is a fast process both temporally and physically due to the rotation of the sample, and to-date, only reflection interference(1) and scattering studies(2) have been made, which only sample an average of the surface have been possible. Modern advances in LED technology and triggering, and the sensitivity of electron-multiplier-charged coupled devices (EMCCD) now allow for the direct observation of this process and we have applied this for the in-situ observation of phase separation in polymer blends. Our results provide direct, irrefutable evidence for the evolution of the final morphologies that result from these blends and coupled to parallel laser scattering experiments we are able to understand and visualise this fast, non-equilibrium process with previously unseen detail. The use of near-monochromatic light also allows for the determination of the rate of thinning through interference effect and coupled with ellipsometry and atomic force microscopy (of the final film) the 3D topography of the film can be reconstructed for all stage of the spin-coating process. 1.D. P. Birnie, Journal of Non-Crystalline Solids 218, 174 (Sep, 1997).2.S. Y. Heriot, R. A. L. Jones, Nature Materials 4, 782 (Oct, 2005).
Dawen Li The University of Alabama
Graciela Blanchet Nano Terra, Inc.
Takao Someya The University of Tokyo
Bruce Gnade University of Texas-Dallas
Xing Cheng Texas A&M University
T6: Vapor Jet, Spray, and Screening Printing
Thursday AM, April 28, 2011
Room 3007 (Moscone West)
9:30 AM - **T6.1
Organic Vapor Jet Printing: A Path to Direct Patterning of Ultrasmall, High Performance Organic Electronics.
Stephen Forrest 1 , Gregory McGraw 1 Show Abstract
1 Physics, Electrical and Computer Engineering, University of Michigan, Ann Arbor, Michigan, United States
The process of organic vapor jet printing (OVJP) is based on the transport of organic molecules in a hot inert carrier gas, through a nozzle to a proximally located, cooled substrate where the organic molecules condense[1, 2]. The dimensions of the deposit are primarily determined by the nozzle diameter, and the nozzle-to-substrate separation distance. OVJP has several advantages over other solution-based patterning techniques such as injet printing. In OVJP, there is no dependence on the mechanical properties (e.g. surface tension) of the solvent, and the electronic properties of the deposited materials are not traded off against the demands of compatibility with the solvent. Furthermore, since the solvent in OVJP is a gas, it is highly volatile, leaving no residue behind following deposition, and multiple organic layers can be deposited without concern for dissolution of previously deposited materials. In this talk, we will discuss recent advances in OVJP that have been achieved using micron-scale nozzle arrays fabricated using conventional and scalable silicon-on-insulator microelectromechanical systems processing technologies. Nozzles 20 μm in width have been used to deposit the active region of high efficiency phosphorescent organic light emitting devices, and calculations show that patterns ~1 μm are achievable by this patterning technology. Furthermore, we discuss prospects for OVJP to print full color, high definition displays as a practical solution to rapidly produce large scale video displays and illumination sources.M. S. Arnold, G. C. McGraw, R. R. Lunt, and S. R. Forrest, "Direct Vapor Jet Printing of Three Color Segment Organic Light Emitting Devices for White Light Illumination," Appl. Phys. Lett., vol. 92, p. 053301, 2008.M. Shtein, P. Peumans, J. B. Benziger, and S. R. Forrest, "Direct printing of molecular organic semiconductors for molecular electronics," Adv. Mat., vol. 16, p. 1615, 2004.
10:00 AM - **T6.2
Organic Integrated Circuits Using High-definition Screen Printing.
Tsuyoshi Sekitani 1 , Takao Someya 1 Show Abstract
1 , University of Tokyo, Tokyo Japan
We report the fabrication of all-printed organic transistor integrated circuits on plastic films using high-definition screen-printing technology. The printing accuracy achieved in this process is 20 μm, and the sheet measures 420 mm along the diagonal. The printed transistors exhibit a mobility of more than 0.1 cm^2/Vs and an on/off ratio greater than 10^5. Large-area active matrices with 1-mm periodicity were constructed using the printed transistors for application to large-area sensors and actuators. Furthermore, high-performance organic complementary circuits were fabricated via screen printing. In this talk, we will discuss the materials, structures, and integration process used in the fabrication of the printed circuits as well as the improvement in the stability of the printed circuits by utilizing new materials and printing processes.This work is partially supported by JST/CREST, Special Coordination Funds for Promoting, and KAKENHI (Wakate S and A).
10:30 AM - **T6.3
Guard Flow-enhanced Organic Vapor Jet Printing of Organic Optoelectronic Materials in Air.
Max Shtein 1 , Shaurjo Biswas 1 , Kyle Luck 1 Show Abstract
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Devices based on small molecular organic compounds are typically fabricated using vacuum thermal evaporation, a capital- and material-intensive method. Consequently, research into novel, alternative deposition techniques has grown in recent years, aiming to address the challenge of processing cost, speed and efficiency. Guard Flow-enhanced Organic Vapor Jet Printing (GF-OVJP) is an additive patterning technique, in which a carrier gas picks up and delivers organic molecules onto a substrate in a high (e.g. sonic) velocity jet, while a specially designed guard flow of inert gas focuses and shields the stream of the source material from the surroundings. The latter modification collimates the deposit, and allows the transport and condensation of the organic vapor to take place in a highly localized fashion, in an inert micro-environment, enabling the printing of device layers in air. We demonstrate the ability of GF-OVJP to deposit organic light emitting layers and light absorbing layers for OLEDs and OPV cells, respectively, as well as the ability to deposit parylene-based encapsulating films. The resulting device performance is shown to improve with guard flow, ultimately achieving parity with vacuum-deposited analogues, even at extremely high local deposition rates (e.g. >500 Angstroms / second). The key transport mechanisms in GF-OVJP will be discussed, along with their influence on film and device properties.
11:30 AM - T6.4
Efficient Polymer Solar Cells Fabricated by Spray Deposition Method.
Byung-Kwan Yu 1 , Doojin Vak 1 2 , Jang Jo 1 3 , Seok-In Na 1 4 , Seok-Soon Kim 1 5 , Dong-Yu Kim 1 Show Abstract
1 Heeger Center for Advanced Materials, Department of Materials Science and Engineering, Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology (GIST), Gwangju Korea (the Republic of), 2 , Commonwealth Scientific and Industrial Research Organisation Molecular and Health Technologies (CSIRO), Clayton South, Vic. 3169, Victoria, Australia, 3 , University of California, Santa Barbara, California, United States, 4 , Korea Institute of Advanced Composite Materials, Korea Institute of Science and Technology (KIST), Wanju-gun Korea (the Republic of), 5 , Kunsan National University, Kunsan Korea (the Republic of)
Polymer solar cells (PSCs) are an attractive option for cost-effective, large area, flexible photovoltaic device applications. Although, there has been a great deal of research regarding new materials for the PSCs and their efficiency, the processing technologies have received relatively less attention. One of the attractions of solution processed polymer solar cells (PSCs) is the potential for low cost production by high throughput roll-to-roll processes. Polymer solar cells can be fabricated by using various solution processes such as spin coating, doctor blading, inkjet printing, and so on. Among these solution processes, the spray process is one of the most promising due to its high production speed and compatibility with various substrates, because the spraying droplets are transferred from the spray nozzle to the substrate without direct contact with the surface. The spray process allows for patterning of the coated film at the sub-millimeter scale through a shadow mask. In addition, the spray process uses much more dilute solutions than the spin-coating method, allowing for the use of various organic materials that have poor solubility in solvents. However an overly rough surface of the conventional sprayed active layer result in a relatively low fill factor (FF) and a high series resistance (Rs). In this study, we demonstrate a technique involving the spraying of additional high boiling point solvent after the formation of the active layer using conventional spray process. After using this technique, we obtain a much smoother surface morphology and ordered bulk heterojuction morphology through enhanced self-organization of the composite materials. Consequently, on the basis of the result, the device with additional high boiling point solvent spray recorded an enhanced efficiency (3.76%) with a high FF value (0.65).
11:45 AM - T6.5
Organic Thin-film Transistors Based on Sprayed TIPS-Pentacene.
William Durant 1 , Jihua Chen 2 , John Anthony 3 , Ilia Ivanov 2 , Dawen Li 1 , Kai Xiao 2 , David Geohegan 2 Show Abstract
1 Department of Electrical and Computer Engineering, University of Alabama, Tuscaloosa, Alabama, United States, 2 Center for Nanophase Materials Sciences, Oak Ridge National Lab, Oak Ridge, Tennessee, United States, 3 Department of Chemistry, University of Kentucky, Lexington, Kentucky, United States
Organic thin-film transistors (OTFTs) based on 6,13-bis(triisopropyl-silylethynyl)-pentacene (TIPS-pentacene) polycrystalline films keep attracting researchers’ interest due to their relatively high mobility, air stable, and the ability to be solution-processed at room temperature. TIPS-pentacene based OTFTs are promising for the next-generation novel and low-cost electronics over large-area flexible substrates. However, TIPS-pentacene thin films severely suffer from crystal growth anisotropy, which consequently results in poor consistency of device performances. In order to solve this problem and take advantages of organic electronics, spray technique was employed to deposit TIPS-pentacene thin films. By using an ultrasonic spray to deposit the TIPS-pentacene solution we were able to assure reproducible TIPS-pentacene morphology with consistent crystal growth orientation. With optimized spray parameters, uniform crystalline growth across a substrate was obtained with a deposition time of less than 45 seconds per 2.5cm2 substrate. Top contact OTFTs with sprayed TIPS-pentacene (8mg TIPS-pentacene to 1mL Toluene) as active layer consistently demonstrate high mobilities (up to 0.32 cm2 V-1 s-1). Optical microscopy, Raman spectroscopy, and x-ray diffraction were employed to investigate the thin film morphology and crystal structures. These investigations show that ultrasonically sprayed TIPS-pentacene thin films could be reproduced with high-quality consistent crystal orientation, which results in uniform OTFT performance over substrates. The scalable spray technique allows us to explore the possibilities of fabricating reproducible, air stable, high mobility OTFTs at room temperature over a large-area flexible substrate in a fraction of the time.
12:00 PM - T6.6
ITO-free Approach for Low Cost, Efficient and Stable Organic Photovoltaics.
Yulia Galagan 1 , Ronn Andriessen 1 , Paul Blom 1 , Nadia Grossiord 1 , Date Moet 1 , Sjoerd Veenstra 2 , Wiljan Verhees 2 , Jan Kroon 2 , Paul Pex 2 Show Abstract
1 , Holst Centre, Eindhoven Netherlands, 2 , ECN, Petten Netherlands
The biggest motivation for the technology development for organic solar cells is the low cost potential, based on the use of low-cost materials and substrates and the very high production speeds that can be reached by roll-to-roll printing and coating. Apart from low cost, to have an impact on the power generation market on the longer term, organic photovoltaics should combine high power conversion efficiency and long term stability. The presence of a transparent conductive electrode such as indium-tin oxide (ITO) limits the reliability and significantly increases the cost of organic photovoltaic devices as it is brittle and expensive. Moreover, the relative high sheet resistance of an ITO electrode on flexible substrates limits the maximum width of a single cell. We have developed an alternative ITO-free transparent anode, based on the solution processed high conductive PEDOT:PSS in combination with a printed current collecting grid. The screen printed silver grids demonstrate a typical sheet resistance of 1 Ohm/sq with 6.4–8% surface coverage. Over-coating of the grid with PEDOT:PSS successfully done due to embedding of the current-collecting silver grid into the substrate. Procedure of embedding creates very flat surface for the deposition of the next function layers in the photovoltaic devices. Replacement of ITO by current-collecting grid and high conducting PEDOT demonstrates that the individual cell dimensions can be substantially larger without decreasing cell performance. Furthermore, as this composite anode is solution-processed, it is a step forward towards low-cost large area processing. Moreover, initial experiments indicate that the intrinsic stability of ITO-free devices is better than the stability of standard devices based on ITO.
12:15 PM - T6.7
Guided Self-assembly of Block-copolymer for Patterning Perpendicular CoPt Magnetic Media.
Zhenzhong Sun 1 4 , Hao Su 3 4 , Anusha Natarajarathinam 2 4 , Subhadra Gupta 2 4 , Dawen Li 1 4 Show Abstract
1 Electrical Engineering, The University of Alabama, Tuscaloosa, Alabama, United States, 4 Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, Alabama, United States, 3 Materials Science Program, The University of Alabama, Tuscaloosa, Alabama, United States, 2 Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, Alabama, United States
Bit-patterned perpendicular magnetic media have been proposed for next-generation recording media due to ultra-high data storage capacity in the order of 1012 bits/in2. In such media, each bit of data is stored in a discrete single domain magnetic nanostructure with feature size around 20-30 nm. Guided self-assembly of block copolymers (BCPs) has been considered to be the most effective way to create periodic high-density bit-patterns at low cost over a large area. In this work, polystyrene (PS)-block-polyferrocenylydimenthylsilane (PFS) diblock copolymer, was employed to pattern perpendicular anisotropy Co80Pt20 films into nanopillar arrays. The magnetic CoPt thin films were deposited by sputtering, and negative resist HSQ was applied on the top of CoPt films by electron-beam lithography to make guide patterns for BCP self-assembly. Ordered spherical-nanopatterns were obtained thorough microphase separation of PS-b-PFS, in which PFS component forms periodic spherical domains within a PS matrix. PS matrix was removed by reactive ion etching in oxygen. The revealed PFS spherical domains serve as ion milling masks for transferring spherical PFS nanopatterns into Co80Pt20 magnetic thin films. PFS has high etching resistance because of the Fe element in the molecule, which provides a great advantage to PS-b-PFS diblock copolymers for creating high aspect ratio bit-patterns. Atomic force microscopy (AFM) was employed to investigate the morphology of PS-b-PFS films at different annealing conditions. Structural characterization of Co80Pt20 continuous films were characterized by XRD and TEM, and patterned periodic nanopillars of less than 10 nm size were imaged by SEM and TEM. Magnetic properties of both continuous and patterned films, such as dynamic coercivity, nucleation field and switching field distribution, were studied using an alternating gradient field magnetometer (AGM) and magneto-optical Kerr effect magnetometer. Furthermore, magnetic force microscopy (MFM) was used to study the domain structure in bit-patterned perpendicular media. Our results show that guided self-assembly of PS-b-PFS provides a promising way to pattern perpendicular magnetic media at low cost over a large area.
12:30 PM - T6.8
Synthesis of Sub-10 nm Single Nanoparticles by Scanning Probe Block Copolymer Lithography.
Jinan Chai 1 2 , Chad Mirkin 1 2 Show Abstract
1 Department of Chemistry, Northwestern University, Evanston, Illinois, United States, 2 International Institute for Nanotechnology, Northwestern University, Evanston, Illinois, United States
Nanoparticles exhibit size-dependent photonic, electronic, and chemical properties that could lead to a new generation of catalysts and nanodevices, including single electron transistors, photonics, and biomedical sensors. In order to realize many of these targeted applications, researchers need ways of synthesizing monodisperse particles while controlling individual particle position on technologically relevant surfaces. The challenge of positioning or synthesizing single sub-10 nm nanoparticles in desired locations is difficult, if not impossible, via current techniques including conventional photolithography. Scanning probe-based methods such as Dip-Pen Nanolithography (DPN) and Polymer Pen Lithography (PPL) are particularly attractive because inked nanoscale tips can deliver material directly to desired locations on various substrates with high registration and sub-50 nm feature resolution. Here we report a novel approach which enables one to control individual nanoparticle growth and position in situ by using DPN or PPL to pattern attoliter volumes of metal ions associated with block copolymers in a massively parallel manner over large areas. Reduction of the metal ions via plasma or electron beam treatment results in the high yield formation of single nanoparticles per block copolymer feature. We demonstrate that pattern dimensions and metal ion concentration dictate the size of each nanoparticle, whose diameter can be controlled down to sub-5 nm.
T7: Miscellaneous Technologies and Applications
Thursday PM, April 28, 2011
Room 3007 (Moscone West)
2:30 PM - **T7.1
Low-voltage Operating Organic Field-effect Transistors for Robust Printed Electronics.
Magnus Berggren 1 , Lars Herlogsson 1 , Xavier Crispin 1 , Jiang Liu 1 , Isak Engquist 1 , Oscar Larsson 1 Show Abstract
1 Organic Electronics, ITN, Linkoping University, Norrkoping Sweden
Future printed electronics require development of a transistor circuit technology that operates at high switching speed and at a low driving voltage to enable powering using printed batteries, electromagnetic induction etc. Moreover, such transistor technology should be possible to manufacture using standard printing techniques and possible to integrate using a robust device and circuit architecture to enable flexibility, easy manufacturing, stability during operation etc.Here, we report an organic field effect transistor (OFET) technology based on gating via a polyelectrolytes. First, the polarization characteristics of such gate “insulators” is presented along with drain current transient characteristics while included in OFET structures. The high polarization characteristics of the thin film polyelectrolytes provide low-voltage operation (1 V) and drain current switch speeds are found in the region from 10 ms to 50 ms. Then, we continue reporting using such polyelectrolyte-gated OFETs in various test circuits, such as in inverters and ring oscillators. The corresponding time delay per stage for 7-stage oscillators is found to be around 0.2 ms. Further, we end our presentation with a discussion and presentation of recent results towards reducing the power in polyelectrolyte-gated OFETs.
3:00 PM - **T7.2
Polymer Solar Cells, Deconstructed.
Yueh-Lin Loo 1 Show Abstract
1 , Princeton University, Princeton, New Jersey, United States
We have successfully constructed polymer solar cells having bulk-heterojunction as well as bilayer structures by soft-contact lamination. This process entails fabricating and processing functional components individually; these separate components are then brought together in a final step to complete the devices. Physical contact occurs non-destructively at room temperature and ambient pressures so this process is particularly suitable for manipulating chemically and mechanically fragile organics. In the construction of inverted polymer solar cells having bulk-heterojunction structures, this process involves a substrate that supports the bottom electrode and the active layer of the polymer solar cells as well as an elastomeric substrate that supports the top electrodes. Lamination of the top substrate against the bottom substrate establishes electrical contact. Given the modularity of this process, the top electrodes can be readily removed after post-deposition processing and device testing so the once-buried active layer can be characterized. This interface is otherwise inaccessible in devices that are fabricated by conventional bottom-up approaches. Grazing-incidence x-ray diffraction carried out on the once-buried interface of inverted polymer solar cells of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) indicates that PCBM crystallinity, as opposed to P3HT crystallinity, increases significantly when the devices are annealed at higher temperatures. Quantification of two-dimensional x-ray patterns indicate PCBM readily adopts the triclinic crystal structure, with the (302) planes of the crystals preferentially oriented parallel to the substrate. This enhancement in PCBM crystallinity and its preferential orientation correlates positively with the measured short circuit current densities during device testing . In the same vein, we have been able to delaminate the active layer from the bottom electrode to expose the organic-metal interface for electronic characterization. The electronic band gap measured at this interface, believed to be that between the ionization potential of P3HT and the electron affinity of PCBM, is 1.5 eV; this value is significantly larger than the band gap one would have expected by examining the energy levels of the individual constituents, likely due to the presence of interfacial dipoles when P3HT and PCBM are intimately mixed .  J.B. Kim et al., “Reversible Soft-Contact Lamination and Delamination for Non-Invasive Fabrication and Characterization of Bulk-Heterojunction and Bilayer Organic Solar Cells,” Chemistry of Materials 22, 4931, 2010. Z. Guan et al., “Direct Determination of the Electronic Structure of the Poly(3-hexylthiophene):phenyl-[6,6]-C61 Butyric Acid Methyl Ester Blend,” Organic Electronics 11, 1779, 2010.
3:30 PM - T7.3
Highly Aligned Printed Organic Nanowires for Large Area Transistor Arrays and Nano-lithography.
Sung-Yong Min 1 , Tae Sik Kim 1 , Tae-Woo Lee 1 Show Abstract
1 Materials Science and Engineering, POSTECH, Pohang Korea (the Republic of)
According to the information technology trend toward highly-integrated and high-performance electronic devices, need for nano-scale devices is increasing. Semiconducting nanowires with the most representative one dimensional nano-structure possess many attractive properties for application to the electronic devices. There are published several methods for preparing organic nanowires (ONWs). However, they have some problems to be solved; alignment, positioning, patterning, etc. We realized the highly aligned semiconducting polymer nanowire arrays by using a electrohydrodynamic nozzle printer which contains the precision linear motor stage-collector. By doping the poly(9-vinylcarbazole) (PVK) with emitting dopants, we have fabricated the well-aligned, multi-color fluorescent nanowires due to the Förster energy transfer. By combining primary blue, green, red fluorescent nanowires, white-light emission was demonstrated in nanowire arrays. Furthermore, we applied the ONW printing method to fabricate the highly aligned nanowire field-effect transistors (FETs) based on poly(3-hexylthiopehene): poly(ethyleneoxide) (P3HT:PEO) blend (80:20, w/w) which showed a high mobility of 0.0148 cm2V-1s-1. With our ONW printing technique, we can control the position of each nanowires precisely to such a degree that is possible to define the number of wire one by one. P3HT:PEO blend nanowire FETs with different number of wires were fabricated and their electrical characteristics were measured. On the other hand, we also demonstrated the organic nanowire lithography to make nano-patterns. We fabricated the large-area metal nano patterns by using the highly aligned nanowire array as a shadow mask for metal vacuum deposition. By using our organic nanowire lithography, we have successfully fabricated the P3HT:PEO blend nanowire FETs which has channel length (~340 nm) and width (~300 nm) in nanometer regime, which showed a field-effect mobility of 0.009 cm2V-1s-1. Our strategy to print the organic nanowires and fabricate their devices in precisely controlled manner can be one of most promising approaches for realizing flexible or textile electronics in large area.
3:45 PM - T7.4
Large-scale Analysis of Neurite Growth Dynamics Using Micropatterned Protein Substrates.
Zachary Wissner-Gross 1 2 , Mark Scott 3 2 , David Ku 3 , Priya Ramaswamy 3 , Mehmet Yanik 3 Show Abstract
1 Physics, Harvard University, Cambridge, Massachusetts, United States, 2 Health, Science, and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
During both development and regeneration of the nervous system, neurons display complex growth dynamics, and several neurites compete to become the neuron’s single axon. Numerous mathematical and biophysical models have been proposed to explain this competition, but these models remain experimentally unverified. Large-scale, precise, and repeatable measurements of neurite dynamics have been difficult to perform, since neurons have varying numbers of neurites, which themselves have complex morphologies. To overcome these challenges using a minimal number of primary neurons, we laser patterned hundreds of identical micron-wide stripes of adhesive proteins on an otherwise highly non-adherent substrate in order to generate repeatable neuronal morphologies on a large scale. By analyzing thousands of quantitative time-lapse measurements of the resulting neurite growth dynamics, we show that total neurite growth accelerates until neurons polarize, that immature neurites compete even at very short lengths, and that neuronal polarity exhibits a distinct transition as neurites grow. Proposed neurite growth models agree only partially with our experimental observations, and simple yet specific modifications can significantly improve these models. The protein patterning and high-content analysis presented here could also be employed in chemical and target-based screens on a variety of complex and subtle phenotypes for therapeutic discoveries using minimal numbers of primary neurons.
4:30 PM - T7.5
Kinetically Controlled Micromechanical Inking and Printing of Nano-objects Using Nanoindentation .
Evelyn Doherty 1 2 , Werner Blau 1 2 , Graham Cross 1 2 Show Abstract
1 Crann (Centre for Research on Adaptive Nanostructures and Nanodevices), Trinity College Dublin, Dublin Ireland, 2 School of Physics, Trinity College Dublin, Dublin Ireland
Investigations were conducted of the micromechanical inking and printing of nano-objects in a controlled way using solid polymers in a nanoindentation system. This kinetically controlled transfer is done without the use of additional chemicals or processes, allowing for the precise placement of structures for electronics and plastic electronics applications. The transfer of objects is controlled by tuning the unload velocities, adhesions and temperatures, thus influencing the energy dissipation and energy release rate of the interface. Attempts at understanding the energy dissipation of the interfaces are described using the Johnson-Kendall-Roberts formulation for elastic contacts and viscoelastic theory. Specifically, networks of single wall carbon nanotubes have been transferred and comparisons made of different configurations, shapes and sizes of portions of the networks. These objects have been printed to different materials including plastics and glass.
4:45 PM - T7.6
Direct-write of Si, Ge, and SiGe Nanostructures Using Conducting Stamps.
Marco Rolandi 1 , Michael Brasino 1 , Vamsi Talla 3 1 , Stephanie Vasko 2 1 , Adnan Kapetanovic 1 Show Abstract
1 Materials Science and Engineering, University of Washington, Seattle, Washington, United States, 3 Electrical Engineering, University of Washington, Seattle, Washington, United States, 2 Chemistry, University of Washington, Seattle, Washington, United States
The high-speed fabrication of Si, Ge, and SiGe heterostructures with nanoscale accuracy is a challenging pursuit essential for novel advances in electronics and photonics. We have recently developed a novel approach for the direct-write of Si, Ge, and SiGe nanostructures in which the biased tip of an atomic force microscope (AFM) locally reacts an organometallic liquid precursor (diphenylsilane and diphenylgermane). Here, we present recent efforts in improving the throughput by using conducting stamps that mimic multiple AFM tips working in parallel. Microscale and nanoscale features on gold-coated PDMS stamps are used to locally react diphenylsilane and diphenylgermane when a bias is applied. In this fashion, high quality and carbon-free (SIMS, x-ray PEEM, TEM) Si, Ge, and SiGe heterostructures with deterministic placement, size, and composition control are produced on extended areas of the substrate. Strategies for wafer scale and roll-to-roll nanostructure direct-write will be discussed.
5:00 PM - T7.7
Direct-write Assembly of Functional Inks for Conductive Microstructures.
Eric Duoss 1 4 , Bok Ahn 1 , David Lorang 1 , Jacob Adams 2 , Thomas Malkowski 1 , Michael Motala 3 , Ralph Nuzzo 3 , Jennifer Bernhard 2 , Jennifer Lewis 1 Show Abstract
1 Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 Center for Micro- and Nanotechnologies, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3 Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
The ability to pattern functional inks via high-speed and low-cost techniques is required for printed electronics to gain widespread acceptance in emerging applications, including sensors, displays, solar cells, and RFID tags. Direct-write assembly is a low-cost, maskless printing route that enables rapid design and patterning of planar and three-dimensional (3D) conductive architectures. In this filamentary printing approach, a concentrated ink with tailored rheological properties is extruded through a tapered cylindrical nozzle that is translated using a three-axis positioning stage. Recent advances in the development of nanoparticle and sol-gel inks for direct-write assembly will be discussed with an emphasis on printing flexible, spanning, and, even, transparent microelectrodes for electronic and optoelectronic devices, such as solar microcell arrays, LED arrays, and 3D electrically small antennas.
5:15 PM - T7.8
Fast, High-throughput Micro, Nanoparticle Printing with Sub – 10 Micron Resolution via Porous Silicon Membrane.
Sun Choi 1 2 , Albert Pisano 1 2 , Tarek Zohdi 2 Show Abstract
1 Berkeley Sensor and Actuator Center(BSAC), UC Berkeley, Berkeley, California, United States, 2 Department of Mechanical Engineering, UC Berkeley, Berkeley, California, United States
We report a novel technique to print micro, nanoparticle assembly with sub - 10 micron resolution by using porous silicon membrane-based printing head. Creating regular, repetitive and well-defined three-dimensional patterns of particle assembly in targeted area is a major bottleneck in various applications such as the fabrication of three-dimensional photonic crystals, printed electronics on flexible substrates, colloidal quantum-dot based devices for display, plasmonics and etc. Conventional approaches to print micro, nanoparticles - inkjet printing, roll-to-roll printing, gravure printing, or photo-template assisted evaporative self-assembly are still majorly suffering from numerous constraints such as low-throughput, low resolution, compatibility with various substrates or incapability of large area patterning. In order to reduce processing time and cost for large-scale manufacturing of optical, electronic devices, it is crucial to develop innovative, novel governing platforms to print various kinds of micro, nanoparticles with high speed and throughput. In this presented work, micro, nanoparticles are printed via porous silicon membrane of a newly designed printing head. The printing head is fabricated by applying conventional micro-fabrication technology to SOI (Silicon-On-Insulator) substrates. Holes of the printing head are defined by photolithography and reactive-ion-etching is followed. Backside is etched by TMAH wet etching in order to define a reservoir region to contain micro, nanoparticle suspension. After the fabrication of a die-size, printing head, this head is attached to a handling wafer and this handling wafer-printing head complex is directly attached to the mask holder of conventional UV-exposure system. Micron-precision, three-axis stage controller of the UV-exposure system enables the printing head to locate the targeted area with accurate alignment. After containing the suspension in the reservoir, direct contact of the head with substrate is performed to transfer multiple micron-size droplets from the bulk suspension the reservoir to the substrate through porous membranes. Rapid-evaporation of these small droplets leads to fast printing of the particles in a high-throughput manner. As a result, printing of small-size particle assembly with sub- 10 micron resolution has been achieved within a few seconds with high-throughput and yield. This result indicates the presented process can be easily extended to large area printing with a capability of multi-layer process. It is anticipated this technique will be applied to large-scale manufacturing of pre-patterned substrates for SERS (Surface Enhanced Raman Spectroscopy), nanoparticle-based conductometric bio-chem sensors and circuitry of printed electronics.