Selected Publications using SonoPlot's Microplotter Systems
Patterning Liquid Crystalline Organic Semiconductors
via Inkjet Printing for High-Performance Transistor Arrays and Circuits
Xiaochen Fang, Jialin Shi, Xiujuan Zhang, Xiaobin Ren, Bei Lu, Wei Deng, Jiansheng Jie, and Xiaohong Zhang
Liquid crystalline (LC) organic semiconductors having long-range-ordered
LC phases hold great application potential in organic field-effect transistors (OFETs). However, to meet real device application requirements, it is a prerequisite to precisely pattern the LC film at desired positions. Here, a facile method that combines the technique of inkjet printing and melt processing to fabricate patterned LC film for achieving high-performance organic integrated circuits is demonstrated. Inkjet printing controls the deposition locations of the LC materials, while the melt processing implements phase transition
of the LC materials to form high-quality LC films with large grain sizes. This approach enables to achieve patterned growth of high-quality 2,7-dioctyl[1]- benzothieno[3,2-b][1]benzothiophene (C8-BTBT) LC films. The patterned C8-BTBT LC film-based 7 × 7 OFET array has 100% die yield and shows high average mobility of 6.31 cm2 V−1 s−1, along with maximum mobility up to 9.33 cm2 V−1 s−1. As a result, the inverters based on the patterned LC films reach a high gain up to 23.75 as well as an ultrahigh noise margin over 81.3%. Given the good generality of the patterning process and the high quality of the resulting films, the proposed method paves the way for high-performance organic integrated devices.
Combined Printing of Highly Aligned Single-Walled Carbon Nanotube Thin Films with Liquid Metal for Direct Fabrication of Functional Electronic Devices
Qian Li and Jing Liu
Latest progress in research and development of advanced materials con- taining single-walled carbon nanotubes (SWCNTs) has considerably improved their wide-spread and large-scale practical applications in cutting-edge electronic devices. One difficult challenge lies in the controllable fabrication of large arrays of very well aligned SWCNTs with a predetermined direction and density. Here, a printing technique that precisely implements accurate long-range SWCNT self-assembly on SiO2/Si substrates modified with octadecyltrichlorosilane (OTS) is introduced. The process is performed using a potential microflow inside SWCNT suspensions on a smooth hydrophobic OTS-treated surface. Such printing strategy can be further developed to align and assemble other various nanotubes and nanowires. In particular, the CNT array and the newly emerging room-temperature liquid metal (LM) with intrinsically excellent conductivity and enormous bendability are suc- cessfully combined for the first time. This enabled direct making of the first ever printed high-performance LM–aligned SWCNT solar cells, transistors, and optoelectronic devices with excellent flexibility. In addition, the realized devices are rather uniform over large areas, which is one of the most impor- tant requirements for mass production. The present achievement suggests an important way toward low cost and large-scale manufacturing of next generation flexible electronic devices, and also will significantly advance LM integrated functional electronics.
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Perovskite quantum dot microarrays: In situ fabrication via direct print photo polymerization
Xiu Liu, Jianjun Li, Pingping Zhang, Weitong Lu, Gaoling Yang, Haizheng Zhong and Yuejin Zhao
Quantum dots color conversion (QDCC) is considered as a facial and versatile way to achieve full-color organic light emitting diode (OLED) and micro-LED display due to the wide color gamut performance and easy integration. However, the aggregation of QDs and coffee-ring effects after solvent evaporation lowers the light conversion efficiency and emission uniformity in QDs microarrays, raising blue-light leakage or optical crosstalk. Here, we report the fabrication of perovskite quantum dots (PQDs) microarrays by combining the inkjet printing and in situ fabrication of PQDs during the photopolymerization of precursor ink. The resulting PQDs microarrays exhibit three-dimensional (3D) morphology with hemisphere shape as well as strong photoluminescence, which is desirable for QDCC applications. We demonstrate the dominant role of ultraviolet (UV) curable precursors and surface functionalized substrate in controlling the shape of microarrays, where significantly increased contact angle (100°) and large height to diameter ratio (0.42) can be achieved. We further demonstrate the potential use of the in situ direct print photopolymerization method for fabricating large-area multicolor patterned pixel microarrays with a wide color gamut and high resolution. The fabrication of 3D PQDs microarrays opens up new opportunities in a variety of applications including photonics integration, micro-LED, and near-field display.
Wearable pressure sensor based on MXene/single-wall carbon nanotube film with crumpled structure for broad-range measurements
Zhihong Fan, Lei Zhang, Qiulin Tan, Xue Yao, Baimao Lin, Ya Wang and Jijun Xiong
High-performance flexible pressure sensors are attracting great interest owing to their potential applications for electronic skins, human–machine interfaces, and biomedical diagnostics. However, there remain significant challenges for the fabrication of low-cost and high-sensitivity sensors. Here, we report the preparation of Ti3C2Tx MXene/single-wall carbon nanotube (SWNT) composite films through vacuum-assisted filtration followed by thermal shrinkage. SWNTs can effectively prevent MXenes from stacking and improve the electrical performance of the films. The films are used as a flexible piezoresistive sensor for pressures ranging from 33 Pa to 130 kPa. And experimental test results indicate that the fabricated pressure sensors have high sensitivity (116.15 kPa−1 below 40 kPa and 12.7 kPa−1 at 40–130 kPa), a fast response time of 13 ms, and long-term stability over 6000 periods. The sensor can be used to monitor human physiological signals, such as finger movements, voice detection, and wrist pulse in real-time. Moreover, a 4 × 4 sensor array was successfully applied in the pressure distribution mapping of different objects, indicating that the pressure sensor can be applied in electronic skin, medical devices, and other wearable devices.
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Fully Printed Stretchable Thin-Film Transistors and Integrated Logic Circuits
Le Cai, Suoming Zhang, Jinshui Miao, Zhibin Yu, and Chuan Wang
This paper reports intrinsically stretchable thin-film transistors (TFTs) and integrated logic circuits directly printed on elastomeric polydimethylsiloxane (PDMS) substrates. The printed devices utilize carbon nanotubes and a type of hybrid gate dielectric comprising PDMS and barium titanate (BaTiO3) nanoparticles. The BaTiO3/PDMS composite simultaneously provides high dielectric constant, superior stretchability, low leakage, as well as good printability and compatibility with the elastomeric substrate. Both TFTs and logic circuits can be stretched beyond 50% strain along either channel length or channel width directions for thousands of cycles while showing no significant degradation in electrical performance. This work may offer an entry into more sophisticated stretchable electronic systems with monolithically integrated sensors, actuators, and displays, fabricated by scalable and low-cost methods for real life applications.
Flat-Panel Laser Displays Based on Liquid Crystal Microlaser Arrays
Fa Feng Xu, Yong Jun Li, Yuanchao Lv, Haiyun Dong, Xianqing Lin, Kang Wang, Jiannian Yao & Yong Sheng Zhao
Laser displays, benefiting from the characteristic merits of lasers, have led to the revolution of next-generation display technologies owing to their superior color expression. However, the acquisition of pixelated laser arrays as self-emissive panels for flat-panel laser displays remains challenging. Liquid crystal (LC) materials with excellent processability and optoelectronic properties offer considerable potential for the construction of highly ordered multicolor laser arrays. Here, we demonstrate flat-panel laser displays on LC microlaser pixel arrays through a microtemplate-assisted inkjet printing method. Individual organic red-green-blue (RGB) microlaser pixel arrays were obtained by doping dyes into LCs with photonic band edges to obtain single-mode RGB lasing, leading to a much broader color gamut, compared with the standard RGB color space. Then we acquired periodically patterned RGB pixel matrices by positioning LC microlasers precisely into highly ordered arrays, according to the well-organized geometry of the microtemplates. Subsequently, we demonstrated full-color flat-panel laser displays using the LC microlaser pixel matrices as self-emissive panels. These results provide valuable enlightenment for the Introduction Laser displays take advantage of high monochromaticity and brightness of laser emissions. They have emerged as revolutionary technologies in the display industries DOI: 10.31635/ccschem.020.202000162 CCS Chem. 2020, 2, 369–375 construction of next-generation flat-panel laser dis- play devices.
Programmable on-chip DNA compartments as artificial cells
Eyal Karzbrun,(1) Alexandra M. Tayar,(1) Vincent Noireaux,(2) Roy H. Bar-Ziv(1).
Department of Materials and Interfaces, Weizmann Institute of Science, (2) Department of Physics, University of Minnesota
(2014).
The assembly of artificial cells capable of executing synthetic DNA programs has been an important goal for basic research and biotechnology. We assembled two-dimensional DNA compartments fabricated in silicon as artificial cells capable of metabolism, programmable protein synthesis, and communication. Metabolism is maintained by continuous diffusion of nutrients and products through a thin capillary, connecting protein synthesis in the DNA compartment with the environment. We programmed protein expression cycles, autoregulated protein levels, and a signaling expression gradient, equivalent to a morphogen, in an array of interconnected compartments at the scale of an embryo. Gene expression in the DNA compartment reveals a rich, dynamic system that is controlled by geometry, offering a means for studying biological networks outside a living cell.
Solution Processable Transistors and Switches: Plotter Printing and Spray Deposition of Materials
Petro Lutsyk, Marcin Sojka, Krzysztof Janu, Juliusz Sworakowski.
Wroclaw University of Technology (2014).
Organic electronic devices, like field-effect transistors (FETs) or switches, have received extensive attention because of their potential application in flexible electronics, large-area displays, radio-frequency identification tags (RFIDs), sensors, etc. Crucial advantage of organic electronics rests in a prospect of low cost manufacturing of electronic circuits achievable by deposition of electronic components from solution by, e.g, ink-jet printing and spray coating. The printing is desirable in the case of fine structures like interdigitated electrodes while spray brushing is more effective for fabrication of large area thin films.
A common challenge in most printing techniques is the limitation in feature size. The line width of 20-100 um is achievable with standard ink-jet printers. The size of printed features may be decreased down to a few microns using laster-assisted technique at the price, however, of a dramatic increase of the cost of fabrication. One of the ways of obtaining small-size features of printed elements may be paved by plotter printing. Advantage of the plotting technique is possibility of drawing very smooth lines enabling one to achieve short (ca 5 um) channel between source and drain electrodes.
Designing hybrid gate dielectric for fully printing high-performance carbon nanotube thin film transistors
Qian Li, Shilong Li, Dehua Yang, Wei Su, Yanchun Wang, Weiya Zhou, Huaping Liu and Sishen Xie
The electrical characteristics of carbon nanotube (CNT) thin-film transistors (TFTs) strongly depend on the properties of the gate dielectric that is in direct contact with the semiconducting CNT channel materials. Here, we systematically investigated the dielectric effects on the electrical characteristics of fully printed semiconducting CNT-TFTs by introducing the organic dielectrics of poly(methyl methacrylate) (PMMA) and octadecyltrichlorosilane (OTS) to modify SiO2 dielectric. The results showed that the organic-modified SiO2 dielectric formed a favorable interface for the efficient charge transport in s-SWCNT-TFTs. Compared to single-layer SiO2 dielectric, the use of organic–inorganic hybrid bilayer dielectrics dramatically improved the performances of SWCNT- TFTs such as mobility, threshold voltage, hysteresis and on/off ratio due to the suppress of charge scattering, gate leakage current and charge trapping. The transport mechanism is related that the dielectric with few charge trapping provided efficient percolation pathways for charge carriers, while reduced the charge scattering. High density of charge traps which could directly act as physical transport barriers and significantly restrict the charge carrier transport and, thus, result in decreased mobile carriers and low device performance. Moreover, the gate leakage phenomenon is caused by conduction through charge traps. So, as a component of TFTs, the gate dielectric is of crucial importance to the manufacture of high quality TFTs from the aspects of affecting the gate leakage current and device operation voltage, as well as the charge carrier transport. Interestingly, the OTS-modified SiO2 allows to directly print horizontally aligned CNT film, and the corresponding devices exhibited a higher mobility than that of the devices with the hybrid PMMA/SiO2 dielectric although the thickness of OTS layer is only ∼2.5 nm. Our present result may provide key guidance for the further development of printed nanomaterial electronics.
Electrical and Mechanical Properties of Ink Printed Composite Electrodes on Plastic Substrates
Xinda Wang, Wei Guo, Ying Zhu, Xiaokang Liang, Fude Wang and Peng Peng
Printed flexible electrodes with conductive inks have attracted much attention in wearable electronics, flexible displays, radio-frequency identification, etc. Conventional conductive inks contain large amount of polymer which would increase the electrical resistivity of as-printed electrodes and require high sintering temperature. Here, composite electrodes without cracks were printed on polyimide substrate using binder-free silver nanoparticle based inks with zero-dimensional (activated carbon), one-dimensional (silver nanowire and carbon nanotube) or two-dimensional (graphene) fillers. The effect of fillers on resistivity and flexibility of printed composite electrodes were evaluated. The graphene filler could reduce the resistivity of electrodes, reaching 1.7 × 10−7 Ω·m after low power laser sintering, while the silver nanowire filler improved their flexibility largely during bending tests. The microstructural changes were examined to understand the nanojoining process and their properties.
Fabrication of high quality and low cost microlenses on a glass substrate by direct printing technique
Zhigang Zang, Xiaosheng Tang, Xianming Liu, Xiaohua Lei, and Weiming Chen
The fabrication of high quality and low cost microlenses on a glass substrate using a simple, rapid, and precise direct microplotting technique is shown in this paper. The fabrication method is based on the use of a microplotter system, which is significantly different from the existing inkjet, roll-to-roll printing, and reactive ion etching technology and could work with higher viscosity materials. By optimizing the param- eters of voltage, dispense time, and concentration of the polymer solution, high quality microlenses with a diameter of 20 μm could be obtained. The geometrical and optical characteristics of the microlenses are analyzed by measurement of the surface profile and the imaging properties in the near-field and far-field zones as well as the diffraction pattern. We think that the fabricated microlenses could be attractive for enhancing the light extraction efficiency of light emitting diodes.
Full-color laser displays based on organic printed microlaser arrays
Jinyang Zhao, Yongli Yan, Zhenhua Gao, Yuxiang Du, Haiyun Dong, Jiannian Yao and Yong Sheng Zhao
Laser displays, which exploit characteristic advantages of lasers, represent a promising next- generation display technology based on the ultimate visual experience they provide. How- ever, the inability to obtain pixelated laser arrays as self-emissive full-color panels hinders the application of laser displays in the flat-panel sector. Due to their excellent optoelectronic properties and processability, organic materials have great potential for the production of periodically patterned multi-color microlaser arrays. Here, we demonstrate for the first time full-color laser displays on precisely patterned organic red-green-blue (RGB) microlaser matrices through inkjet printing. Individual RGB laser pixels are realized by doping respective luminescent dyes into the ink materials, resulting in a wide achievable color gamut 45% larger than the standard RGB space. Using as-prepared microlaser arrays as full-color panels, we achieve dynamic laser displays for video playing through consecutive beam scanning. These results represent a major step towards full-color laser displays with outstanding color expression.
Microstructured Silicone Substrate for Printable and Stretchable Metallic Films
Adam P. Robinson, Ivan Minev, Ingrid M. Graz, and Stephanie P. Lacour.
Nanoscience Centre, Department of Engineering, University of Cambridge (2011).
Stretchable electronics (i.e., hybrid inorganic or organic circuits integrated on elastomeric substrates) rely on elastic wiring. We present a technique for fabricating reversibly stretchable metallic films by printing silver-based ink onto microstructured silicone substrates. The wetting and pinning of the ink on the elastomer surface is adjusted and optimized by varying the geometry of micropillar arrays patterned on the silicone substrate. The resulting films exhibit high electrical conductivity (!11 000 S/cm) and can stretch reversibly to 20% strain over 1000 times without failing electrically. The stretchability of the g200 nm thick metallic !lm relies on engineered strain relief in the printed !lm on patterned PDMS.
Ink-plotting of YBa2Cu3O7-x- filamented structures
A.Kirchner(1), R. Hühne(1), I. Birlik(1), P. Vermeir, (2) I. Van Driessche (2), L. Schultz1, B. Holzapfel(1). (1)IFW Dresden, Institute for Metallic Materials, (2)Dep. Inorganic and Physical Chemistry, Ghent University (2011).
Chemical Solution Deposition (CSD) is a promising process for industrial long length production of high temperature superconducting tapes because of its low-cost, high-speed production and good scalability. YBa2Cu3O7-x (YBCO) coated conductors are the favourable material with excellent superconducting properties including sufficient high Jc-performance. Nevertheless, the alternating current (ac)-losses are still too high for applications of wires in motors. A special plotting technique allows a printing of filamented structures of YBCO thin layers. The hysteresis losses in such striped films are much lower than in continuously coated substrates with a homogeneous YBCO layer.
Lines as well as rectangular shaped YBCO-structures were deposited by an ink plotting system on single crystal substrates. Different inks were tested, among them an environmentally friendly, water-based fluorine-free YBCO precursor solution as well as an ink, synthesised according to the TFA route.
A High Throughput, High Resolution Enzymatic Lithography Process: Effect of Crystallite Size, Moisture and Enzyme Concentration
Zhantong Mao; Manoj Ganesh; Michael Bucaro; Igor Smolianski; Richard A. Gross; Alan M. Lyons. Department of Chemistry, College of Staten Island, City University of New York, Department of Chemistry and Biology, Rensselaer Polytechnic Institute, SyntheZyme LLC (2014).
By bringing enzymes into contact with predefined regions of a surface, a polymer film can be selectively degraded to form desired patterns that find a variety of applications in biotechnology and electronics. This so-called "enzymatic lithography" is an environmentally friendly process as it does not require actinic radiation or synthetic chemicals to develop the patterns. A significant challenge to using enzymatic lithography has been the need to restrict the mobility of the enzyme in order to maintain control of feature sizes. Previous approaches have resulted in low throughput and were limited to polymer films only a few nanometers thick. In this paper, we demonstrate an enzymatic lithography system based on Candida antartica lipase B (CALB) and poly(ε-caprolactone) (PCL) that can resolve fine-scale features, (<1 μm across) in thick (0.1-2.0 μm) polymer films. A Polymer Pen Lithography (PPL) tool was developed to deposit an aqueous solution of CALB onto a spin-cast PCL film. Immobilization of the enzyme on the polymer surface was monitored using fluorescence microscopy by labeling CALB with FITC. The crystallite size in the PCL films was systematically varied; small crystallites resulted in significantly faster etch rates (20 nm/min) and the ability to resolve smaller features (as fine as 1 μm). The effect of printing conditions and relative humidity during incubation is also presented. Patterns formed in the PCL film were transferred to an underlying copper foil demonstrating a "Green" approach to the fabrication of printed circuit boards.
Patterned Enzymatic Degradation of Poly(ε-caprolactone) by High- Affinity Microcontact Printing and Polymer Pen Lithography
Manoj Ganesh, Jonathan Nachman, Zhantong Mao, Alan Lyons, Miriam Rafailovich, and Richard Gross. Polytechnic Institute of NYU, State University of New York at Stony Brook, College of Staten Island (CUNY) (2013).
This paper reports deposition of Candida antarctica Lipase B (CALB) on relatively thick poly(ε-caprolactone) (PCL) films (300−500 nm) to create well-defined patterns using two different writing techniques: high-affinity microcontact (HA-μCL) and polymer pen (PPL) lithography. For both, an aqueous CALB ink is absorbed onto a polydimethylsiloxane (PDMS) writing implement (PDMS stamp or a PDMS pen tip), which is transferred to a spun-cast PCL film. HA-μCL experiments demonstrated the importance of applied pressure to obtain high-resolution patterns since uniform contact is needed between raised 20 μm parallel line regions of the PDMS stamp and the surface. AFM imaging shows pattern formation evolves gradually over incubation time only in areas stamped with CALB cutting through spherulites without apparent influence by grain boundaries. Strong binding of CALB to PCL is postulated as the mechanism by which lateral diffusion is limited. PPL enables formation of an arbitrary image by appropriate programming of the robot. The PDMS pen tips were coated with an aqueous CALB solution and then brought into contact with the PCL film to transfer CALB onto the surface. By repeating the ink transfer step multiple times where pen tips are brought into contact with the PCL film at a different locations, a pattern of dots is formed. After printing, patterns were developed at 37 °C and 95% RH. Over a 7-day period, CALB progressively etched the PCL down to the silicon wafer on which it was spun (350 nm) giving round holes with diameters about 10 μm. AFM images show the formation of steep PCL walls indicating CALB degraded the PCL film in areas to which it was applied. This work demonstrates that high-resolution patterns can be achieved without immobilizing the enzyme on the surface of polymeric stamps that limits the depth of features obtained as well as the throughput of the process.
Fully Printed Separated Carbon Nanotube Thin Film Transistor Circuits and Its Application in Organic Light Emitting Diode Control
Pochiang Chen,† Yue Fu,‡ Radnoosh Aminirad,†,§ Chuan Wang,‡ Jialu Zhang,‡ Kang Wang,§ Kosmas Galatsis,*,†,§ and Chongwu Zhou.†Aneeve Nanotechnologies LLC, ‡Department of Electrical Engineering, University of Southern California, §Department of Electrical Engineering, University of California at Los Angeles (2011).
The advantages of printed electronics and semi-conducting single-walled carbon nanotubes (SWCNTs) are combined for the #rst time for display electronics. Conductive silver ink and 98% semiconductive SWCNT solutions are used to print back-gated thin #lm transistors with high mobility, high on/off ratio, and high current carrying capacity. In addition, with printed polyethylenimine with LiClO4 as the gating material, fully printed top-gated devices have been made to work as excellent current switches for organic light emitting diodes (OLEDs). An OLED driving circuit composed of two top-gated fully printed transistors has been fabricated, and the successful control over external OLED is demonstrated. Our work demonstrates the signi#cant potential of using printed carbon nanotube electronics for display backplane applications.
Glycocalyx remodeling with proteoglycan mimetics promotes neural specification in embryonic stem cells.
Mia L. Huang, Raymond A. A. Smith, Greg W. Trieger, and Kamil Godula. Department of Chemistry and Biochemistry, University of California, San Diego, California 92093-0358, United States (2014).
Growth factor (GF) signaling is a key determinant of stem cell fate. Interactions of GFs with their receptors are often mediated by heparan sulfate proteoglycans (HSPGs). Here, we report a cell surface engineering strategy that exploits the function of HSPGs to promote differentiation in embryonic stem cells (ESCs). We have generated synthetic neoproteoglycans (neoPGs) with affinity for the fibroblast growth factor 2 (FGF2) and introduced them into plasma membranes of ESCs deficient in HS biosynthesis. There, the neoPGs assumed the function of native HSPGs, rescued FGF2-mediated kinase activity, and promoted neural specification. This glycocalyx remodeling strategy is versatile and may be applicable to other types of differentiation.
Cold-plasma modification of oxide surfaces for covalent biomolecule attachment.
B. J. Larson, J. M. Helgren, S. O. Manolache, A. Y. Lau, M. G. Lagally, and F. S. Denes. Biosensors and Bioelectronics 21, 796-801 (2005).
While many processes have been developed to modify the surface of glass and other oxides for biomolecule attachment, they rely primarily upon wet chemistry and are costly and time-consuming. We describe a process that uses a cold plasma and a subsequent in vacuo vapor-phase reaction to terminate a variety of oxide surfaces with epoxide chemical groups. These epoxide groups can react with amine-containing biomolecules, such as proteins and modified oligonucleotides, to form strong covalent linkages between the biomolecules and the treated surface. The use of a plasma activation step followed by an in vacuo vapor-phase reaction allows for the precise control of surface functional groups, rather than the mixture of functionalities normally produced. By maintaining the samples under vacuum throughout the process, adsorption of contaminants is effectively eliminated. This process modifies a range of different oxide surfaces, is fast, consumes a minimal amount of reagents, and produces attachment densities for bound biomolecules that are comparable to or better than commercially available
substrates.
Polymer light emitting diodes and poly(di-n-octylfluorene) thin films as fabricated with a microfluidics applicator.
H. Cheun, P. P. Rugheimer, B. J. Larson, P. Gopalan, M. G. Lagally, and M. J. Winokur. Journal of Applied Physics 100, 073510 (2006).
A microfluidics applicator is used in the fabrication of a polyfluorene based polymer light emitting diode (PLED). This procedure results in a single contiguous polymer trace and, as a consequence of the high deposition speed, shows unusual characteristics in both the film morphology and polymer microstructure. These aspects are studied using fluorescence microscopy, profilometry, and optical absorption and emission pectroscopies. Room temperature analysis of the poly (di-n-octylfluorene) indicates that the combination of high-speed deposition and rapid drying process traps the polymer into a metastable conformational state. Optical spectroscopy at reduced temperature identifies emission from at least two distinct conformational chromophores. At elevated temperature there is an abrupt, irreversible transition to a more conventional structural form. Electroluminesence data from PLED test devices are shown and this demonstrates some of the unique opportunities afforded by this method of polymer film formation and device fabrication. Device operation is not optimized.
Guided Formation of Large Crystals of Organic and Perovskite Semiconductors by an Ultrasonicated Dispenser
Chenning Liu, Hang Zhou, Qian Wu, Fuhua Dai, Tsz-Ki Lau, Xinhui Lu, Tengzhou Yang, Zixin Wang, Xuying Liu,∥ and Chuan Liu
The crystallization of organic or perovskite semiconductors reflects the intermolecular interactions and crucially determines the charge transport in opto-electronic devices. In this report, we demonstrate and investigate the use of an ultrasonicated dispenser to guide the formation of crystals of organic and perovskite semiconductors. The moving speed of the dispenser affects the match between the concentration gradient and evaporation rate near the three-phase contact lines and thus the generation of various crystallization morphologies. The mechanism of crystallization is given by a relationship between the calculated concentration gradient profile and the degree of crystal alignment. Highly ordered, aligned crystals are achieved for both organic bis(triisopropylsilylethynyl)-pentacene and perovskite MAPbI3 semiconductors. Absorption spectra, Raman scattering spectroscopy analysis, and grazing incidence wide-angle X-ray scattering measurement reveal the strong anisotropy of the crystalline structures. The aligned crystals lead to remarkably enhanced electrical performances in an organic thin-film transistor (OTFT) and perovskite photodetector. As a demonstration, we combine the OTFT with photodetectors to achieve an active matrix of normally off, gate-tunable photodetectors that operate under ambient conditions.
Controlled deposition of picoliter amounts of fluid using an ultrasonically driven micropipette.
B.J. Larson, S.D. Gillmor, and M.G. Lagally. Review of Scientific Instruments 75, 832-836 (2004).
A fluid microplotter that uses ultrasonics to deposit small fluid features has been constructed. It consists of a dispenser, composed of a micropipette fastened to a piece of lead zirconate titanate piezoelectric, attached to a precision positioning system. When an electrical signal of the appropriate frequency and voltage is applied, solution in the tip of the micropipette wicks to the surface in a controlled fashion. The gentle pumping of fluid to the surface occurs when the micropipette is driven at frequencies in the range of 400 - 700 kHz. Spots with diameters smaller than several microns can be deposited in this manner. Continuous lines can also be produced. Several examples of deposited patterns and structures are described. This means of deposition represents a higher-resolution alternative to standard fluid deposition techniques in the fabrication of biological microarrays or polymer-based circuits.
New technologies for fabricating biological microarrays
B. J. Larson. Ph.D. thesis, University of Wisconsin-Madison (2005).
Microarrays, composed of thousands of spots of different biomolecules attached to a solid substrate, have emerged as one of the most important tools in modern biological research. This dissertation contains the description of two technologies that we have developed to reduce the cost and improve the quality of spotted microarrays.
The first is a device, called a fluid microplotter, that uses ultrasonics to deposit spots with diameters of less than 5 microns. It consists of a dispenser, composed of a micropipette fastened to a piece of PZT piezoelectric, attached to a precision positioning system. A gentle pumping of fluid to the surface occurs when the micropipette is driven at specific frequencies. Spots or continuous lines can be deposited in this manner. The small fluid features conserve expensive and limited-quantity biological reagents. Additionally, the spots produced by the microplotter can be very regular, with coefficients of variability for their diameters of less than 5%.
We characterize the performance of the microplotter in depositing fluid and examine the theoretical underpinnings of its operation. We present an analytical expression for the diameter of a deposited spot as a function of droplet volume and wettability of a surface and compare it with experimental results. We also examine the resonant properties of the piezoelectric element used to drive the dispenser and relate that to the frequencies at which pumping occurs. Finally, we propose a mechanism to explain the pumping behavior within the microplotter dispenser.
The second technology we present is a process that uses a cold plasma and a subsequent in vacuo vapor-phase reaction to terminate a variety of oxide surfaces with epoxide chemical groups. These epoxide groups can react with amine-containing biomolecules, such as proteins and modified oligonucleotides, to form strong covalent linkages between the biomolecules and the treated surface. The use of a plasma activation step followed by an in vacuo vapor-phase reaction allows for the precise control of surface functional groups, rather than the mixture of functionalities normally produced. By maintaining the samples under vacuum throughout the process, adsorption of contaminants is effectively eliminated. This process modifies a range of different oxide surfaces, is fast, consumes a minimal amount of reagents, and produces attachment densities for bound biomolecules that are comparable to or better than commercially available substrates.
We show applications of these two technologies in the fabrication of protein microarrays, enhancement of MALDI mass spectrometry, deposition of polymer electronics, directed growth of carbon nanotubes, and the chemical modification of carbon-containing materials.