Gyoujin Cho

As recent developments in noninvasive biosensors spearhead the thrust toward personalized health and fitness monitoring, there is a need for high throughput, cost-effective fabrication of flexible sensing components. Toward this goal, we present roll-to-roll (R2R) gravure printed electrodes that are robust under a range of electrochemical sensing applications. We use inks and electrode morphologies designed for electrochemical and mechanical stability, achieving devices with uniform redox kineti

A 20 × 20 pixel pressure sensor array based on a printed active-matrix single-wall carbon-nanotube thin-film transistor backplane is presented. Using a gravure printing process that is compatible with fully printed large-area roll-to-roll processing, a 97% device yield is obtained on the 400-transistor backplane. As a proof of concept, pressure sensors are integrated to map the applied tactile pressure across the array.

Wireless power transmission to inexpensive and disposable smart electronic devices is one of the key issues for the realization of a ubiquitous society where sensor networks such as RFID tags, price tags, smart logos, signage and sensors could be fully interconnected and utilized by DC power of less than 0.3 W. This DC power can be provided by inductively coupled AC from a 13.56 MHz power transmitter through a rectenna, consisting of an antenna, a diode and a capacitor, which would be cheap to i

Abstract A limitless‐length flexible active‐matrix implies that virtually any surface can be rendered into an interactive medium when laminated with electrophoretic or organic light‐emitting diode sheets. However, performance, cost, and size limitations of current fabrication technologies and semiconducting materials, typically utilized in thin film transistor (TFT) active matrices (TFT‐AMs), have hindered progress, thus preventing the realization of fully printed TFT‐AMs on a plastic roll. A ne

The instability of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) under a humid condition is the major limitation in the practical development of a flexible thermistor. Here, we introduced a functionalized graphene oxide-polyvinylidene fluoride (FGO-PVDF) composite as an encapsulation layer to prove the reliability of PEDOT:PSS thermistors under high-humidity conditions. The FGO-PVDF-encapsulated thermistor exhibited good linearity, a resolution of 1272.57 Ω per °C, a tempera

Abstract Printed electronics have been considered to bring about the ICT (Information Communication Technology) revolution. The high-throughput production of the ultra-low-cost printed devices along with the level of integration of logic gates via an all roll-to-roll (R2R) printing method has been the major axes in the revolution. However, there have been certain concerns related to the integration of logic gates via the R2R printing methods. This review paper focuses on the key issues that must

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 highli

Abstract Printed electronics are challenged for showing the working concept of the roll‐to‐roll (R2R) printed 13.56 MHz passive radio frequency identification (RFID) tag for the application in wireless identification (ID) and authentication to prevent counterfeits with the cost of a penny. However, the concept of the penny RFID tag is not successful yet because of the major limit in integrating a number logic gates by a high throughput R2R printing method. Herein, a new way of printed electronic

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 car

Abstract Roll‐to‐roll (R2R) printed electronics have been considered as the holy grail for the low‐cost manufacturing of expendable and compliant electronic devices. However, a lapse exists in unlocking the full potential of R2R printed electronics in that there has yet to be a R2R foundry able to integrate complementary metal‐oxide‐semiconductor (CMOS) logic gates into such devices. Herein, a R2R printing foundry based on a complementary design rule of physical dimension in which the rheology o

Printed p-type single walled carbon nanotube (SWCNT) based circuits exhibit high power dissipation owing to their thick printed dielectric layers (>2 μm) and long channels (>100 μm). In order to reduce the static power dissipation of printed SWCNT-base circuits while maintaining the same printing conditions and channel lengths, complementary metal-oxide-semiconductor (CMOS) based circuits are more ideal. These circuits, however, have not been successfully implemented in a scalable printing platf

Abstract As new authentic products are introduced into the market, counterfeiting has always been on the rise. In 2015, the global economic loss caused by counterfeiting is more than 1.7 trillion US dollars and has been increasing annually. Therefore, an inexpensive but efficient anti‐counterfeiting platform must be developed to end counterfeiting. Here, a wireless platform for the anti‐counterfeiting with an item‐tracking is developed by integrating printed four key‐device units, a 13.56 MHz re

Abstract Formulating a high‐performing semiconducting ink is crucial toward printing a diode for constructing a direct current (DC) power harvesting device, consisting of an antenna, a diode, and a capacitor, that can rectify the coupled weak near field communication (NFC) (13.56 MHz) signal (<1.5 Vpp) generated from smartphones. To achieve such performance, indium gallium zinc oxide (IGZO)‐based semiconducting ink is formulated by developing an electroactive binder, poly(4‐styrene sulfonic a