Jinsoo Noh

All-Printed and Roll-to-Roll-Printable 13.56-MHz-Operated 1-bit RF Tag on Plastic Foils

An all-printed rectifier that can provide at least 10 V dc from a 13.56-MHz radio frequency identification (RFID) reader and an all-printed ring oscillator that can generate at least 100 Hz of clock signal to read a 96-bit RFID tag in a second under the dc power provided by the rectifier should first be printable on plastic foils for the realization of roll-to-roll (R2R) printed ultralow cost RFID tags. Here, we describe a practical way to provide all-printed and R2R-printable antenna, rectifiers, and ring oscillators on plastic foils and demonstrate 13.56-MHz-operated 1-bit RF tags. The all-printed and R2R-printable 13.56-MHz 1-bit tags can generate 102.8 Hz of clock signal as the tag approaches the 13.56-MHz RFID reader.

Scalability of Roll-to-Roll Gravure-Printed Electrodes on Plastic Foils

Roll-to-roll (R2R) gravure printing is considered to be a leading technology for the production of flexible and low-cost printed electronics in the near future. To enable the use of R2R gravure in printed electronics, the limits of overlay printing registration accuracy (OPRA) and the scalability of printed features with respect to the physical parameters of the gravure system, including given plastic substrates and inks, should be characterized. Important parameters of printed lines include surface roughness, thickness, line widening, and line-edge roughness. To date, there are no comprehensive reports regarding the limits of OPRA and the scalability of printed electrodes, including the control of surface roughness, thickness, line widening, and line-edge roughness using R2R gravure printing. In this paper, we examine ways of evaluating the OPRA limit of our gravure system. We find that OPRA is limited in the web moving direction to 40 μm and in the perpendicular direction to 16 μm, showing the importance of web handling on registration. Furthermore, we demonstrate the scalability of printed electrodes formed using a R2R gravure system to linewidths of 317 μm, with 440 nm thickness, 30 nm of surface roughness and edge waviness of 4 μm on PET foils, and describe optimization strategies to realize improved surface roughness, thickness, line widening, and line-edge roughness for future printed electronics applications.

Fully Gravure-Printed D Flip-Flop on Plastic Foils Using Single-Walled Carbon-Nanotube-Based TFTs

Since D flip-flop is one of the indispensable building blocks in integrated circuit (IC) design, providing a successful way to print D flip-flop on plastic foils will be the first step to reach fully printed flexible IC. Here, the network structure of single-walled carbon nanotubes (SWNTs) as an active layer has been employed to print the driver and load thin-film transistors (TFTs) of the D flip-flop. The same physical dimensions of driver and load TFTs were first developed to fully gravure print the D flip-flop because of the advantage of tunable electrical properties of network density of SWNTs. Therefore, the circuit design and printing becomes simpler and more convenient than using general design rules. Furthermore, the SWNT network structure in the active layer can also minimize the fluctuation of threshold voltages (Vth) of SWNT-TFTs because of the use of the same physical dimensions in TFTs. The resulting gravure-printed D flip-flop shows a clock-to-output delay of 23 ms for 20-Hz clock signal. This is the first reported D flip-flop performance using all gravure-printing method yet achieved.

Fully roll-to-roll gravure printed rectenna on plastic foils for wireless power transmission at 13.56 MHz

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 integrate with inexpensive smart electronic devices. To integrate the rectenna with a minimum cost, a roll-to-roll (R2R) gravure printing process has been considered to print the rectenna on plastic foils. In this paper, R2R gravure printing systems including printing condition and four different nanoparticle based inks will be reported to print the rectenna (antenna, diode and capacitor) on plastic foils at a printing speed of 8 m min(-1) and more than 90% device yield for a wireless power transmission of 0.3 W using a standard 13.56 MHz power transmitter.

A fully roll-to-roll gravure-printed carbon nanotube-based active matrix for multi-touch sensors.

Roll-to-roll (R2R) printing has been pursued as a commercially viable high-throughput technology to manufacture flexible, disposable, and inexpensive printed electronic devices. However, in recent years, pessimism has prevailed because of the barriers faced when attempting to fabricate and integrate thin film transistors (TFTs) using an R2R printing method. In this paper, we report 20 × 20 active matrices (AMs) based on single-walled carbon nanotubes (SWCNTs) with a resolution of 9.3 points per inch (ppi) resolution, obtained using a fully R2R gravure printing process. By using SWCNTs as the semiconducting layer and poly(ethylene terephthalate) (PET) as the substrate, we have obtained a device yield above 98%, and extracted the key scalability factors required for a feasible R2R gravure manufacturing process. Multi-touch sensor arrays were achieved by laminating a pressure sensitive rubber onto the SWCNT-TFT AM. This R2R gravure printing system overcomes the barriers associated with the registration accuracy of printing each layer and the variation of the threshold voltage (Vth). By overcoming these barriers, the R2R gravure printing method can be viable as an advanced manufacturing technology, thus enabling the high-throughput production of flexible, disposable, and human-interactive cutting-edge electronic devices based on SWCNT-TFT AMs.

Fully printed flexible and disposable wireless cyclic voltammetry tag

A disposable cyclic voltammetry (CV) tag is printed on a plastic film by integrating wireless power transmitter, polarized triangle wave generator, electrochemical cell and signage through a scalable gravure printing method. By proximity of 13.56 MHz RF reader, the printed CV tag generates 320 mHz of triangular sweep wave from +500 mV to −500 mV which enable to scan a printed electrochemical cell in the CV tag. By simply dropping any specimen solution on the electrochemical cell in the CV tag, the presence of solutes in the solution can be detected and shown on the signage of the CV tag in five sec. 10 mM of N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) was used as a standard solute to prove the working concept of fully printed disposable wireless CV tag. Within five seconds, we can wirelessly diagnose the presence of TMPD in the solution using the CV tag in the proximity of the 13.56 MHz RF reader. This fully printed and wirelessly operated flexible CV tag is the first of its kind and marks the path for the utilization of inexpensive and disposable wireless electrochemical sensor systems for initial diagnose hazardous chemicals and biological molecules to improve public hygiene and health.

Fully Gravure-Printed Flexible Full Adder Using SWNT-Based TFTs

A single-walled carbon nanotube (SWNT)-based 1-b full-adder circuit was realized on flexible plastic substrates through an all gravure printing process by minimizing intertransistor process variation and leakage current between crossing interconnects. The circuit comprised 27 printed SWNT thin-film transistors, with a variation of up to only ±25% in electrical characteristics among them. Furthermore, the circuit showed a maximum propagation delay of 13.7 ms, with a 50-Hz input signal, and a supply voltage of -20 V. The process could be used for low-cost flexible arithmetic logic units in a variety of applications.

Key Issues With Printed Flexible Thin Film Transistors and Their Application in Disposable RF Sensors

This paper addresses the key issues that must be overcome to realize fully printed TFT-based flexible devices via commercially viable methods. In particular the threshold voltage (Vth) variation in printed TFTs is a serious impediment to the successful launch of fully printed TFT-based devices in the market. The underlying causes of the Vth variation in fully printed TFTs were analyzed by considering the misalignment of printed drain-source to gate electrodes, the rheology of electronic inks and effects from external sources of charge. By alleviating the influences of external sources of charge using a printed passivation layer, Vth variation is maintained below 30% using a fully printed process. Based on the attainable variation range, the required number of integrated TFTs was estimated to fabricate a fully printed TFT-based radio frequency (RF) sensor device. A practical compromise enables fully printed RF sensors to be realized via the scalability of printing processes that mitigate Vth variation by minimizing the level of TFT integration. Prototypes of fully printed RF sensors with human interactive capability-an RF sensor label, and an RF e-sensor (cyclic voltammetry) tag-are enabled with as few as 26 printed TFTs, demonstrating that low-cost and high throughput manufacturing of printed electronics is feasible.

Fully Gravure Printed Half Adder on Plastic Foils

All-printed half adders will be the first step to the way of printing an arithmetic logic unit which will be further expanded to printing microprocessors directly onto flexible plastic foils. In this letter, the half-adder circuit has been constructed using an all gravure printing process on poly(ethylene terephtalate) foils. To successfully operate the printed half adder, we first simulate the half adder using the parameters extracted from gravure-printed single-walled carbon nanotube (SWNT)-based thin-film transistors (TFTs) to provide a tolerable range of fluctuations of electrical parameters of the gravure-printed SWNT-based TFTs. Based on the close comparison between simulation results and attained electrical parameters of printed TFTs, controlling waviness of printed drain-source electrodes has been found to be a key factor for successfully executing the function of a printed half adder on the plastic foils.

Scalability of carbon-nanotube-based thin film transistors for flexible electronic devices manufactured using an all roll-to-roll gravure printing system.

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, BaTiO3 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 (Vth) variations of less than 30% can be maintained.