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Article ; Online: Control of the Drying Patterns for Complex Colloidal Solutions and Their Applications

Saebom Lee / Tiara A. M. / Gyoujin Cho / Jinkee Lee

Nanomaterials, Vol 12, Iss 2600, p

2022 Volume 2600

Abstract: The uneven deposition at the edges of an evaporating droplet, termed the coffee-ring effect, has been extensively studied during the past few decades to better understand the underlying cause, namely the flow dynamics, and the subsequent patterns formed ... ...

Abstract	The uneven deposition at the edges of an evaporating droplet, termed the coffee-ring effect, has been extensively studied during the past few decades to better understand the underlying cause, namely the flow dynamics, and the subsequent patterns formed after drying. The non-uniform evaporation rate across the colloidal droplet hampers the formation of a uniform and homogeneous film in printed electronics, rechargeable batteries, etc., and often causes device failures. This review aims to highlight the diverse range of techniques used to alleviate the coffee-ring effect, from classic methods such as adding chemical additives, applying external sources, and manipulating geometrical configurations to recently developed advancements, specifically using bubbles, humidity, confined systems, etc., which do not involve modification of surface, particle or liquid properties. Each of these methodologies mitigates the edge deposition via multi-body interactions, for example, particle–liquid, particle-particle, particle–solid interfaces and particle–flow interactions. The mechanisms behind each of these approaches help to find methods to inhibit the non-uniform film formation, and the corresponding applications have been discussed together with a critical comparison in detail. This review could pave the way for developing inks and processes to apply in functional coatings and printed electronic devices with improved efficiency and device yield.
Keywords	coffee-ring effect ; evaporation ; interfacial flow ; deposition patterns ; Chemistry ; QD1-999
Subject code	620 ; 600
Language	English
Publishing date	2022-07-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Towards Digital Twin Implementation in Roll-To-Roll Gravure Printed Electronics

Anood Shakeel / Bijendra Bishow Maskey / Sagar Shrestha / Sajjan Parajuli / Younsu Jung / Gyoujin Cho

Nanomaterials, Vol 13, Iss 1008, p

Overlay Printing Registration Error Prediction Based on Printing Process Parameters

2023 Volume 1008

Abstract: Roll-to-roll gravure (R2Rg) has become highly affiliated with printed electronics in the past few years due to its high yield of printed thin-film transistor (TFT) in active matrix devices, and to its low cost. For printing TFTs with multilayer ... ...

Abstract	Roll-to-roll gravure (R2Rg) has become highly affiliated with printed electronics in the past few years due to its high yield of printed thin-film transistor (TFT) in active matrix devices, and to its low cost. For printing TFTs with multilayer structures, achieving a high-precision in overlay printing registration accuracy (OPRA) is a key challenge to attain the high degree of TFT integration through R2Rg. To address this challenge efficiently, a digital twin paradigm was first introduced in the R2Rg system with an aim to optimize the OPRA by developing a predictive model based on typical input variables such as web tension, nip force, and printing speed in the R2Rg system. In our introductory-level digital twin, errors in the OPRA were collected with the variable parameters of web tensions, nip forces, and printing speeds from several R2Rg printing processes. Subsequently, statistical features were extracted from the input data followed by the training of a deep learning long-short term memory (LSTM) model for predicting machine directional error (MD) in the OPRA. As a result of training the LSTM model in our digital twin, its attained accuracy of prediction was 77%. Based on this result, we studied the relationship between the nip forces and printing speeds to predict the MD error in the OPRA. The results indicated a correlation between the MD error in the OPRA and the printing speed, as the MD error amplitude in the OPRA tended to decline at the higher printing speed.
Keywords	roll-to-roll gravure printing ; digital twins ; thin film transistors ; overlay printing registration accuracy ; predictive modeling ; Chemistry ; QD1-999
Subject code	600
Language	English
Publishing date	2023-03-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Rapid Uniformity Analysis of Fully Printed SWCNT-Based Thin Film Transistor Arrays via Roll-to-Roll Gravure Process

Yunhyok Choi / Younsu Jung / Reem Song / Jinhwa Park / Sajjan Parajuli / Sagar Shrestha / Gyoujin Cho / Byung-Sung Kim

Nanomaterials, Vol 13, Iss 590, p

2023 Volume 590

Abstract: The roll-to-roll (R2R) gravure process has the potential for manufacturing single-wall carbon nanotubes (SWCNT)-based thin film transistor (TFT) arrays on a flexible plastic substrate. A significant hurdle toward the commercialization of the R2R-printed ... ...

Abstract	The roll-to-roll (R2R) gravure process has the potential for manufacturing single-wall carbon nanotubes (SWCNT)-based thin film transistor (TFT) arrays on a flexible plastic substrate. A significant hurdle toward the commercialization of the R2R-printed SWCNT-TFT array is the lack of a suitable, simple, and rapid method for measuring the uniformity of printed products. We developed a probing instrument for characterizing R2R gravure printed TFT, named PICR2R-TFT, for rapidly characterizing R2R-printed SWCNT-TFT array that can present a geographical distribution profile to pinpoint the failed devices in an SWCNT-TFT array. Using the newly developed PICR2R-TFT instrument, the current–voltage characteristics of the fabricated SWCNT-TFT devices could be correlated to various R2R-printing process parameters, such as channel length, roll printing length, and printing speed. Thus, by introducing a characterization tool that is reliable and fast, one can quickly optimize the R2R gravure printing conditions to enhance product uniformity, thereby maximizing the yield of printed SWCNT-TFT arrays.
Keywords	roll-to-roll gravure ; thin film transistor arrays ; uniformity ; probing instrument ; Chemistry ; QD1-999
Subject code	600
Language	English
Publishing date	2023-02-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Room temperature roll-to-roll additive manufacturing of polydimethylsiloxane-based centrifugal microfluidic device for on-site isolation of ribonucleic acid from whole blood

Trung Hoang / Han Truong / Jiyeon Han / Saebom Lee / Jihyeong Lee / Sajjan Parajuli / Jinkee Lee / Gyoujin Cho

Materials Today Bio, Vol 23, Iss , Pp 100838- (2023)

2023

Abstract: Polymer-based lab-on-a-disc (LoaD) devices for isolating ribonucleic acid (RNA) from whole blood samples have gained considerable attention for accurate biomedical analysis and point-of-care diagnostics. However, the mass production of these devices ... ...

Abstract	Polymer-based lab-on-a-disc (LoaD) devices for isolating ribonucleic acid (RNA) from whole blood samples have gained considerable attention for accurate biomedical analysis and point-of-care diagnostics. However, the mass production of these devices remains challenging in manufacturing cost and sustainability, primarily due to the utilization of a laser cutter or router computer numerical control (CNC) machine for engraving and cutting plastics in the conventional prototyping process. Herein, we reported the first energy-efficient room-temperature printing-imprinting integrated roll-to-roll manufacturing platform for mass production of a polydimethylsiloxane (PDMS)-based LoaD to on-site isolate ribonucleic acid (RNA) from undiluted blood samples. We significantly reduced energy consumption and eliminated thermal expansion variations between the mold, substrate, and resists by accelerating the PDMS curing time to less than 10 min at room temperature without using heat or ultraviolet radiation. The additive manufacturing technology was applied to fabricate a multi-depth flexible polymer mold that integrated macro (2 mm) and micro-sized (500 μm) features, which overcomes the economic and environmental challenges of conventional molding techniques. Our integrated R2R platform was enabled to print adhesion-promoting films at the first printing unit and continuously in-line imprint with a high replication accuracy (99%) for high-volume manufacturing of a new centrifugal microfluidic chip with an enhancement of mixing performance by integrating an efficient mixing chamber and serpentine micromixer. This research paved the way for scalable green manufacturing of large-volume polymer-based microfluidic devices, often required in real-world sample-driven analytical systems for clinical bioanalysis.
Keywords	Room-temperature PDMS ; Centrifugal microfluidic ; RNA extraction ; Roll-to-roll nanoimprint lithography ; Sustainable manufacturing ; Medicine (General) ; R5-920 ; Biology (General) ; QH301-705.5
Subject code	670
Language	English
Publishing date	2023-12-01T00:00:00Z
Publisher	Elsevier
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Strain Optimization of Tensioned Web through Computational Fluid Dynamics in the Roll-to-Roll Drying Process

Minho Jo / Jaehyun Noh / Gyoujin Cho / Taik-min Lee / Bukuk Oh / Sanghoon Nam / Changwoo Lee

Polymers, Vol 14, Iss 2515, p

2022 Volume 2515

Abstract: Unpredictable web temperature distributions in the dryer and strain deviations in the cross-machine (CMD) and machine (MD) directions could hamper the manufacture of smooth functional layers on polymer-based webs through the roll-to-roll (R2R) continuous ...

Abstract	Unpredictable web temperature distributions in the dryer and strain deviations in the cross-machine (CMD) and machine (MD) directions could hamper the manufacture of smooth functional layers on polymer-based webs through the roll-to-roll (R2R) continuous process system. However, research on this topic is limited. In this study, we developed a structural analysis model using the temperature distribution of the web as a boundary condition to analyze the drying mechanism of the dryer used in an R2R system. Based on the results of this model, we then applied structural modifications to the flow channel and hole density of the aluminum plate of the dryer. The model successfully predicted the temperature and strain distributions of the web inside the dryer in the CMD and MD by forming a tension according to the speed difference of the driven rolls at both ends of the span. Our structural improvements significantly reduced the temperature deviation of the moving web inside the dryer by up to 74% and decreased the strain deviation by up to 46%. The findings can help prevent web unevenness during the drying process of the R2R system, which is essential to minimize the formation of defects on functional layers built over polymer-based webs.
Keywords	computational fluid dynamics (CFD) ; drying process ; roll-to-roll (R2R) ; strain optimization ; tensioned web ; temperature distribution ; Organic chemistry ; QD241-441
Subject code	660
Language	English
Publishing date	2022-06-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Improving Stability of Roll-to-Roll (R2R) Gravure-Printed Carbon Nanotube-Based Thin Film Transistors via R2R Plasma-Enhanced Chemical Vapor-Deposited Silicon Nitride

Sagar Shrestha / Sajjan Parajuli / Jinhwa Park / Hao Yang / Tae-Yeon Cho / Ji-Ho Eom / Seong-Keun Cho / Jongsun Lim / Gyoujin Cho / Younsu Jung

Nanomaterials, Vol 13, Iss 559, p

2023 Volume 559

Abstract: Single-walled carbon nanotubes (SWCNTs) have an advantage in printing thin film transistors (TFTs) due to their high carrier mobility, excellent chemical stability, mechanical flexibility, and compatibility with solution-based processing. Thus, the ... ...

Abstract	Single-walled carbon nanotubes (SWCNTs) have an advantage in printing thin film transistors (TFTs) due to their high carrier mobility, excellent chemical stability, mechanical flexibility, and compatibility with solution-based processing. Thus, the printed SWCNT-based TFTs (pSWCNT-TFTs) showed significant technological potential such as integrated circuits, conformable sensors, and display backplanes. However, the long-term environmental stability of the pSWCNT-TFTs hinders their commercialization. Thus, to extend the stability of the pSWCNT-TFTs, such devices should be passivated with low water and oxygen permeability. Herein, we introduced the silicon nitride (SiNx) passivation method on the pSWCNT-TFTs via a combination of roll-to-roll (R2R) gravure and the roll-to-roll plasma-enhanced vapor deposition (R2R-PECVD) process at low temperature (45 °C). We found that SiNx-passivated pSWCNT-TFTs showed ± 0.50 V of threshold voltage change at room temperature for 3 days and ±1.2 V of threshold voltage change for 3 h through a Temperature Humidity Test (85/85 test: Humidity 85%/Temperature 85 °C) for both p-type and n-type pSWCNT-TFTs. In addition, we found that the SiNx-passivated p-type and n-type pSWCNT-TFT-based CMOS-like ring oscillator, or 1-bit code generator, operated well after the 85/85 test for 24 h.
Keywords	roll to roll ; PECVD ; passivation ; threshold voltage ; silicon nitride ; 85/85 test ; Chemistry ; QD1-999
Subject code	600
Language	English
Publishing date	2023-01-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Web Unevenness Due to Thermal Deformation in the Roll-to-Roll Manufacturing Process

Minho Jo / Jongsu Lee / Seongyong Kim / Gyoujin Cho / Taik-Min Lee / Changwoo Lee

Applied Sciences, Vol 10, Iss 8636, p

2020 Volume 8636

Abstract: In roll-to-roll (R2R) processing, web uniformity is a crucial factor that can guarantee high coating quality. To understand web defects due to thermal deformation, we analyzed the effect of web unevenness on the coating quality of an yttria-stabilized ... ...

Abstract	In roll-to-roll (R2R) processing, web uniformity is a crucial factor that can guarantee high coating quality. To understand web defects due to thermal deformation, we analyzed the effect of web unevenness on the coating quality of an yttria-stabilized zirconia (YSZ) layer, a brittle electrolyte of solid oxide fuel cells (SOFCs). We used finite-element analysis to study thermal and mechanical deformations at different drying temperature levels. A YSZ layer was also coated using R2R slot-die coating to observe the effect of web unevenness on coating quality. Web unevenness was generated by thermal deformation due to conduction and convection heat from the dryer. Because of varying web unevenness with time, the YSZ layer developed cracks. At higher drying temperatures, more coating defects with larger widths were generated. Results indicated that web unevenness at the coating section led to coating defects that could damage the SOFCs and decrease yield in the R2R process. Coating defects generated by web unevenness caused by convection and conduction heat should be considered in the high-volume production of brittle electrolytes using the R2R process.
Keywords	coating defect ; electrolyte layer ; temperature ; thermal deformation ; roll-to-roll slot-die coating systems ; wrinkle ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
Subject code	620
Language	English
Publishing date	2020-12-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Mobile Efficient Diagnostics of Infectious Diseases via On‐Chip RT‐qPCR

Kiran Shrestha / Seongryeong Kim / Jiyeon Han / Gabriela Morales Florez / Han Truong / Trung Hoang / Sajjan Parajuli / Tiara AM / Beomsoo Kim / Younsu Jung / Abdurhaman Teyib Abafogi / Yugyeong Lee / Seung Hyun Song / Jinkee Lee / Sungsu Park / Minhee Kang / Hee Jae Huh / Gyoujin Cho / Luke P. Lee

Advanced Science, Vol 10, Iss 28, Pp n/a-n/a (2023)

MEDIC‐PCR

2023

Abstract: Abstract The COVID‐19 outbreak has caused public and global health crises. However, the lack of on‐site fast, reliable, sensitive, and low‐cost reverse transcription polymerase chain reaction (RT‐PCR) testing limits early detection, timely isolation, and ...

Abstract	Abstract The COVID‐19 outbreak has caused public and global health crises. However, the lack of on‐site fast, reliable, sensitive, and low‐cost reverse transcription polymerase chain reaction (RT‐PCR) testing limits early detection, timely isolation, and epidemic prevention and control. Here, the authors report a rapid mobile efficient diagnostics of infectious diseases via on‐chip ‐RT‐quantitative PCR (RT‐qPCR): MEDIC‐PCR. First, the authors use a roll‐to‐roll printing process to accomplish low‐cost carbon‐black‐based disposable PCR chips that enable rapid LED‐induced photothermal PCR cycles. The MEDIC‐PCR can perform RT (3 min), and PCR (9 min) steps. Further, the cohort of 89 COVID‐19 and 103 non‐COVID‐19 patients testing is completed by the MEDIC‐PCR to show excellent diagnostic accuracy of 97%, sensitivity of 94%, and specificity of 98%. This MEDIC‐PCR can contribute to the preventive global health in the face of a future pandemic.
Keywords	covid‐19 ; diagnostics ; low‐cost ; rapid ; rt‐qpcr ; Science ; Q
Language	English
Publishing date	2023-10-01T00:00:00Z
Publisher	Wiley
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Proving Scalability of an Organic Semiconductor To Print a TFT-Active Matrix Using a Roll-to-Roll Gravure

Junfeng Sun / Hyejin Park / Younsu Jung / Grishmi Rajbhandari / Bijendra Bishow Maskey / Ashish Sapkota / Yasuo Azuma / Yutaka Majima / Gyoujin Cho

ACS Omega, Vol 2, Iss 9, Pp 5766-

2017 Volume 5774

Keywords	Chemistry ; QD1-999
Language	English
Publishing date	2017-09-01T00:00:00Z
Publisher	American Chemical Society
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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