The Experts below are selected from a list of 1446 Experts worldwide ranked by ideXlab platform
Vivek Subramanian - One of the best experts on this subject based on the ideXlab platform.
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Scalability of carbon-nanotube-based thin film transistors for flexible electronic devices manufactured using an all roll-to-roll Gravure Printing system
Scientific Reports, 2015Co-Authors: Hyunmo Koo, Vivek Subramanian, Wookyu Lee, Younchang Choi, Junfeng Sun, Jina Bak, Jinsoo Noh, Yasuo Azuma, Yutaka Majima, Gyoujin ChoAbstract:To demonstrate that roll-to-roll (R2R) Gravure Printing is a suitable advanced manufacturing method for flexible thin film transistor (TFT)-based electronic circuits, three different nanomaterial-based inks (silver nanoparticles, BaTiO_3 nanoparticles and single-walled carbon nanotubes (SWNTs)) were selected and optimized to enable the realization of fully printed SWNT-based TFTs (SWNT-TFTs) on 150-m-long rolls of 0.25-m-wide poly(ethylene terephthalate) (PET). SWNT-TFTs with 5 different channel lengths, namely, 30, 80, 130, 180 and 230 μm, were fabricated using a Printing speed of 8 m/min. These SWNT-TFTs were characterized and the obtained electrical parameters were related to major mechanical factors such as web tension, registration accuracy, impression roll pressure and Printing speed to determine whether these mechanical factors were the sources of the observed device-to-device variations. By utilizing the electrical parameters from the SWNT-TFTs, a Monte Carlo simulation for a 1-bit adder circuit, as a reference, was conducted to demonstrate that functional circuits with reasonable complexity can indeed be manufactured using R2R Gravure Printing. The simulation results suggest that circuits with complexity, similar to the full adder circuit, can be printed with a 76% circuit yield if threshold voltage ( V _ th ) variations of less than 30% can be maintained.
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fabrication of a high resolution roll for Gravure Printing of 2μm features
Organic Field-Effect Transistors XIV; and Organic Sensors and Bioelectronics VIII, 2015Co-Authors: Gerd Grau, Rungrot Kitsomboonloha, Vivek SubramanianAbstract:High-resolution features are key to achieve high performance printed electronics devices such as transistors. Gravure Printing is very promising to achieve high resolution in combination with high Printing speeds on the order of 1m/s. High-speed Gravure has recently been shown to print high resolution features down to linewidths and spacing of 2μm. Whilst this was a tremendous improvement over previous reports, these results had been obtained using silicon Printing plates. These silicon Printing plates are fabricated using microfabrication techniques which offer several advantages over traditional metal Gravure cylinders where the features are defined by techniques such as stylus engraving, laser engraving or etching. This offers much greater precision and design freedom in terms of feature size, surface roughness, cell placement and cell shape. However, rigid silicon Printing plates cannot be used in a roll-to-roll Printing process that would truly enable low-cost printed electronics. Here we demonstrate for the first time a Gravure Printing roll that combines the precision of silicon Printing plates with the form factor of a metal cylinder. The fabrication process starts with a silicon master whose pattern is replicated by polymer molding. The actual metal Printing plate is then built up on the polymer negative of the pattern by a combination of electroless and electroplating. After separation of the polymer and the metal, the metal Printing plate can be mounted on a magnetic roll for Printing. Printing of highly scaled 2μm features is demonstrated. Different metal surfaces were explored to optimize Printing performance and wear during Printing.
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cell filling in Gravure Printing for printed electronics
Langmuir, 2014Co-Authors: Jialiang Cen, Rungrot Kitsomboonloha, Vivek SubramanianAbstract:Highly scaled direct Gravure is a promising Printing technique for printed electronics due to its large throughput, high resolution, and simplicity. Gravure can print features in the single micron range at Printing speeds of ∼1 m/s by using an optimized cell geometry and optimized Printing conditions. The filling of the cells on the Gravure cylinder is a critical process, since the amount of ink in the cells strongly impacts printed feature size and quality. Therefore, an understanding of cell filling is crucial to make highly scaled Gravure printed electronics viable. In this work we report a novel experimental setup to investigate the filling process in real time, coupled with numerical simulations to gain insight into the experimental observations. By varying viscosity and filling speed, we ensure that the dimensionless capillary number is a good indicator of filling regime in real Gravure Printing. In addition, we also examine the effect of cell size on filling as this is important for increasing prin...
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Femtoliter-scale patterning by high-speed, highly scaled inverse Gravure Printing
Langmuir, 2012Co-Authors: Rungrot Kitsomboonloha, S. J.s. Morris, Xiaoying Rong, Vivek SubramanianAbstract:Pattern Printing techniques have advanced rapidly in the past decade, driven by their potential applications in printed electronics. Several Printing techniques have realized printed features of 10 μm or smaller, but unfortunately, they suffer from disadvantages that prevent their deployment in real applications; in particular, process throughput is a significant concern. Direct Gravure Printing is promising in this regard. Gravure Printing delivers high throughput and has a proven history of being manufacturing worthy. Unfortunately, it suffers from scalability challenges because of limitations in roll manufacturing and limited understanding of the relevant Printing mechanisms. Gravure Printing involves interactions between the ink, the patterned cylinder master, the doctor blade that wipes excess ink, and the substrate to which the pattern is transferred. As Gravure-printed features are scaled, the associated complexities are increased, and a detailed study of the various processes involved is lacking. In this work, we report on various Gravure-related fluidic mechanisms using a novel highly scaled inverse direct Gravure printer. The printer allows the overall pattern formation process to be studied in detail by separating the entire Printing process into three sequential steps: filling, wiping, and transferring. We found that pattern formation by highly scaled Gravure Printing is governed by the wettability of the ink to the Printing plate, doctor blade, and substrate. These individual functions are linked by the apparent capillary number (Ca); the printed volume fraction (φ(p)) of a feature can be constructed by incorporating these basis functions. By relating Ca and φ(p), an optimized operating point can be specified, and the associated limiting phenomena can be identified. We used this relationship to find the optimized ink viscosity and Printing speed to achieve printed polymer lines and line spacings as small as 2 μm at Printing speeds as high as ∼1 m/s.
Wangzhou Shi - One of the best experts on this subject based on the ideXlab platform.
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Gravure Printing of hybrid MoS2@S-rGO interdigitated electrodes for flexible microsupercapacitors
Applied Physics Letters, 2015Co-Authors: Yuxiu Xiao, Lei Huang, Qi Zhang, Qi Chen, Wangzhou ShiAbstract:In this letter, we demonstrated Gravure Printing of hybrid MoS2@S-rGO consisting of sulfonated reduced graphene oxide (S-rGO) and MoS2 nanoflowers to obtain a highly porous pattern of interdigitated electrodes, leading to a microsupercapacitor on a flexible polyimide substrate. The in-plane interdigital design of the printed microelectrodes is effective in increasing accessibility of electrolyte ions into the large active surface area. The optimized MoS2@S-rGO microsupercapacitor achieved a high specific capacitance (6.56 mF/cm2), energy density (0.58 mWh/cm3), and power density (13.4 mW/cm3), respectively. In addition, the printed microsupercapacitor lost only 9% of the maximum capacity after 1000 cycles, indicating that the printed hybrid MoS2@S-rGO microsupercapacitors are quite stable for potential flexible device applications.
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Gravure Printing of hybrid mos2 s rgo interdigitated electrodes for flexible microsupercapacitors
Applied Physics Letters, 2015Co-Authors: Yuxiu Xiao, Lei Huang, Qi Zhang, Qi Chen, Wangzhou ShiAbstract:In this letter, we demonstrated Gravure Printing of hybrid MoS2@S-rGO consisting of sulfonated reduced graphene oxide (S-rGO) and MoS2 nanoflowers to obtain a highly porous pattern of interdigitated electrodes, leading to a microsupercapacitor on a flexible polyimide substrate. The in-plane interdigital design of the printed microelectrodes is effective in increasing accessibility of electrolyte ions into the large active surface area. The optimized MoS2@S-rGO microsupercapacitor achieved a high specific capacitance (6.56 mF/cm2), energy density (0.58 mWh/cm3), and power density (13.4 mW/cm3), respectively. In addition, the printed microsupercapacitor lost only 9% of the maximum capacity after 1000 cycles, indicating that the printed hybrid MoS2@S-rGO microsupercapacitors are quite stable for potential flexible device applications.
Dongjin Lee - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of flexible strain sensors via roll-to-roll Gravure Printing of silver ink
Smart Materials and Structures, 2018Co-Authors: Janghoon Park, Dongil Nam, Sungsik Park, Dongjin LeeAbstract:We fabricated flexible printed strain sensors by roll-to-roll (R2R) Gravure Printing of the silver paste on polyimide substrate. The printed sensors with size 10 × 17 mm2 were sintered at high temperature to obtain stable resistance value. The fabricated sensor was attached onto the plastic bar and the strain measurement was performed under bending, tensile, and periodic loadings. The strain sensors showed the gauge factor of 1.99–2.24 and the measurable strain range of −386 × 10−6 to 16 272 × 10−6. It is comparable to that of the commercially available strain gauges and excellent when compared to the previous studies. The R2R-based strain sensor fabrication is expected to be used not only for manufacturing innovation of existing commercial sensors but also for resistor-based emerging wearable devices.
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Optimization of Printing conditions for microscale multiline Printing in continuous roll-to-roll Gravure Printing
Journal of Industrial and Engineering Chemistry, 2016Co-Authors: Jongsu Lee, Kee-hyun Shin, Janghoon Park, Hakyung Jeong, Dongjin LeeAbstract:Abstract This study proposed new criteria for numerical evaluation of the printability of microscale patterns with various Printing defects. Based on these criteria, Printing conditions that could be easily tuned in roll-to-roll Gravure Printing were optimized by a Box–Behnken design of experiment. Under the optimal conditions, sub-30-μm multilines, which have few Printing defects, were obtained. Finally, a dimensionless print quality metric was defined for an objective evaluation of printability based on the proposed criteria following verification of its viability.
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An Investigation of the Ink-Transfer Mechanism During the Printing Phase of High-Resolution Roll-to-Roll Gravure Printing
IEEE Transactions on Components Packaging and Manufacturing Technology, 2015Co-Authors: Ho Anh Duc Nguyen, Changwoo Lee, Kee-hyun Shin, Dongjin LeeAbstract:Reducing the linewidth of electrodes is of high importance for increasing not only the efficiency of photovoltaic devices but also the performance of organic thin-film transistors. In particular, controlling the line pattern in Printing processes has been difficult. In this paper, we report an analytical approach for obtaining high-resolution control over the ink-transfer mechanism in roll-to-roll (R2R) Gravure Printing. A dimensionless adhesion-force difference was defined for a simple ink-transfer model, and it was used to predict and evaluate the ink-transfer mechanism with respect to several parameters, such as the surface tension of the ink, surface energy of the substrate, and surface energy and aspect ratio (AR) of the cell. It was found that the low-surface-tension inks, high-surface-energy substrates, and low-surface-energy and high-AR cells are preferable to increasing the ink-transfer ratio during the Printing phase. Finally, a matching-logic flowchart was developed for controlling the ink-transfer mechanism and fidelity of R2R Gravure Printing. The printed patterns obtained had an average width as small as 15.3 $\mu \text{m}$ (standard deviation $= \,\, 0.9~\mu \text{m}$ ).
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An approach for controlling printed line-width in high resolution roll-to-roll Gravure Printing
Journal of Micromechanics and Microengineering, 2013Co-Authors: Ho Anh Duc Nguyen, Kee-hyun Shin, Jongsu Lee, Chung Hwan Kim, Dongjin LeeAbstract:One of the challenges in printed electronics is the capacity to print a high resolution electrode. However, it is difficult to gain control over fidelity of microscale line-width of printed patterns especially in roll-to-roll (R2R) Gravure Printing process. Here, we report a simple solution based on the wettability of ink on the substrate to prevent a widening effect of printed patterns thereby enhancing the precision. The widening effect was found to be affected by intrinsic (ink wetting behavior, cell geometry) and extrinsic (nip pressure, Printing speed) conditions. Analysis was conducted to figure out an effect of surface tension of ink and surface energy of substrate on the printed pattern width via contact angle (θIS). For a given cell volume, the width of printed patterns decreased with increasing contact angle. The experimental method was used to determine the optimal extrinsic condition and unstable region border. Finally, we identified three ink setting regions of widening (θIS ≤ ), un-widening (
Kee-hyun Shin - One of the best experts on this subject based on the ideXlab platform.
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Approach to optimizing printed conductive lines in high-resolution roll-to-roll Gravure Printing
Robotics and Computer-integrated Manufacturing, 2017Co-Authors: Ho Anh Duc Nguyen, Changwoo Lee, Kee-hyun ShinAbstract:Roll-to-roll Gravure Printing has recently gained considerable interest regarding its application for manufacturing printed electronics, owing to its potential for processing large areas at low costs with high throughput. The geometry of the printed lines depends mainly on the process parameters. Unfortunately, missing areas and well-defined line widths have opposite tendencies. This paper presents a multi-response optimization process for Printing high-resolution conductive lines using roll-to-roll Gravure Printing. Our optimization is based on grey relational analysis and an analysis of variance in conjunction with the Taguchi method, which uses an orthogonal array. Together, these techniques are used to optimize the printed pattern geometry and missing areas. Furthermore, we investigate several parameters for roll-to-roll Gravure Printing, such as ink viscosity, Printing speed, and nip pressure, and the effect of these parameters on the line width, thickness, and missing areas of the printed pattern. Experiments were conducted to evaluate the proposed method, and the results of this evaluation demonstrate an improvement to the well-defined line width, thickness, and continuity of conductive lines under optimal parameter settings using the proposed grey-based Taguchi method. Taguchi method is used to study the effect of Gravure Printing on missing area, line width, and thickness.Grey relational analysis is used to determine the optimal combination of processing parameters.The optimal case are confirmed and compared to initial case and the best case from Taguchis design.
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Multi-response optimization of R2R Gravure Printing using orthogonal array and principal component analysis as a weighting factor
The International Journal of Advanced Manufacturing Technology, 2017Co-Authors: Ho Anh Duc Nguyen, Kee-hyun Shin, Changwoo LeeAbstract:Control over the quality of roll-to-roll Gravure-printed silver-nanoparticle electrodes such as continuity, line width, and thickness is of importance to create high-resolution patterns of low resistance. In this regard, the multi-response optimization of Gravure Printing is required for industrial practice. To address this problem, the Taguchi method coupled with principal component analysis has been applied for multi-objective optimization of roll-to-roll Gravure Printing of silver-nanoparticle electrode to attain optimal condition within design space. The three-quality characteristics including continuity, pattern line width, and pattern thickness were simultaneously considered for optimization. The process parameters with three levels considered are ink viscosity, air nip pressure, and Printing speed. First, Taguchi method was utilized to determine single-objective optimization. Then, the signal-to-noise ratios obtained from Taguchi method were used in principal component analysis to define a weighting factor of three-quality characteristics for multi-objective optimization. Finally, experiments were conducted to evaluate the proposed method, and the results demonstrate an improvement to the well-defined line width, thickness, and continuity of silver-nanoparticle electrodes under optimal parameter settings.
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Optimization of Printing conditions for microscale multiline Printing in continuous roll-to-roll Gravure Printing
Journal of Industrial and Engineering Chemistry, 2016Co-Authors: Jongsu Lee, Kee-hyun Shin, Janghoon Park, Hakyung Jeong, Dongjin LeeAbstract:Abstract This study proposed new criteria for numerical evaluation of the printability of microscale patterns with various Printing defects. Based on these criteria, Printing conditions that could be easily tuned in roll-to-roll Gravure Printing were optimized by a Box–Behnken design of experiment. Under the optimal conditions, sub-30-μm multilines, which have few Printing defects, were obtained. Finally, a dimensionless print quality metric was defined for an objective evaluation of printability based on the proposed criteria following verification of its viability.
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An Investigation of the Ink-Transfer Mechanism During the Printing Phase of High-Resolution Roll-to-Roll Gravure Printing
IEEE Transactions on Components Packaging and Manufacturing Technology, 2015Co-Authors: Ho Anh Duc Nguyen, Changwoo Lee, Kee-hyun Shin, Dongjin LeeAbstract:Reducing the linewidth of electrodes is of high importance for increasing not only the efficiency of photovoltaic devices but also the performance of organic thin-film transistors. In particular, controlling the line pattern in Printing processes has been difficult. In this paper, we report an analytical approach for obtaining high-resolution control over the ink-transfer mechanism in roll-to-roll (R2R) Gravure Printing. A dimensionless adhesion-force difference was defined for a simple ink-transfer model, and it was used to predict and evaluate the ink-transfer mechanism with respect to several parameters, such as the surface tension of the ink, surface energy of the substrate, and surface energy and aspect ratio (AR) of the cell. It was found that the low-surface-tension inks, high-surface-energy substrates, and low-surface-energy and high-AR cells are preferable to increasing the ink-transfer ratio during the Printing phase. Finally, a matching-logic flowchart was developed for controlling the ink-transfer mechanism and fidelity of R2R Gravure Printing. The printed patterns obtained had an average width as small as 15.3 $\mu \text{m}$ (standard deviation $= \,\, 0.9~\mu \text{m}$ ).
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an approach for controlling printed line width in high resolution roll to roll Gravure Printing
Journal of Micromechanics and Microengineering, 2013Co-Authors: Ho Anh Duc Nguyen, Kee-hyun ShinAbstract:One of the challenges in printed electronics is the capacity to print a high resolution electrode. However, it is difficult to gain control over fidelity of microscale line-width of printed patterns especially in roll-to-roll (R2R) Gravure Printing process. Here, we report a simple solution based on the wettability of ink on the substrate to prevent a widening effect of printed patterns thereby enhancing the precision. The widening effect was found to be affected by intrinsic (ink wetting behavior, cell geometry) and extrinsic (nip pressure, Printing speed) conditions. Analysis was conducted to figure out an effect of surface tension of ink and surface energy of substrate on the printed pattern width via contact angle (θIS). For a given cell volume, the width of printed patterns decreased with increasing contact angle. The experimental method was used to determine the optimal extrinsic condition and unstable region border. Finally, we identified three ink setting regions of widening (θIS ≤ ), un-widening (<θIS <) and unstable region (θIS ≥ ). The experimental data showed a good agreement with expected results based on the established analytical approach. This result could be used as an important practical guideline to be applied in R2R Gravure Printing process with high resolution.
Jennifer A Lewis - One of the best experts on this subject based on the ideXlab platform.
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visualization and simulation of the transfer process of index matched silica microparticle inks for Gravure Printing
Aiche Journal, 2017Co-Authors: Arnout Boelens, Sooman Lim, Lorraine F. Francis, Bok Yeop Ahn, Juan J De Pablo, Jennifer A LewisAbstract:A combined experimental and computational study of the transfer of transparent index-matched silica-particle inks between two flat plates is presented for Gravure Printing applications. The influence of Printing speed and initial ink droplet size on the ability to accurately transfer ink during the Printing process is explored systematically. Smooth interface volume of fluid simulations show the same trends as the ink transfer observed in experiments over a wide range of Printing speeds and for inks having different silica particle loadings. Our calculations indicate that for ink droplets with characteristic dimensions in the vicinity of 10 μm, which are of particular interest for Gravure Printing applications, ink transfer improves significantly due to the diminishing effect of gravity, and the increased importance of capillary forces at small length scales. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1419–1429, 2017
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Visualization and simulation of the transfer process of index‐matched silica microparticle inks for Gravure Printing
Aiche Journal, 2016Co-Authors: Arnout Boelens, Sooman Lim, Lorraine F. Francis, Bok Yeop Ahn, Juan J De Pablo, Jennifer A LewisAbstract:A combined experimental and computational study of the transfer of transparent index-matched silica-particle inks between two flat plates is presented for Gravure Printing applications. The influence of Printing speed and initial ink droplet size on the ability to accurately transfer ink during the Printing process is explored systematically. Smooth interface volume of fluid simulations show the same trends as the ink transfer observed in experiments over a wide range of Printing speeds and for inks having different silica particle loadings. Our calculations indicate that for ink droplets with characteristic dimensions in the vicinity of 10 μm, which are of particular interest for Gravure Printing applications, ink transfer improves significantly due to the diminishing effect of gravity, and the increased importance of capillary forces at small length scales. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1419–1429, 2017
