홍용택 교수

The development of highly sensitive pressure sensors with a low-cost and facile fabrication technique is desirable for electronic skins and wearable sensing devices. Here a low-cost and facile fabrication strategy to obtain multiscale-structured elastomeric electrodes and a highly sensitive and robust flexible pressure sensor is presented. The principles of spontaneous buckle formation of the PDMS surface and the embedding of silver nanowires are used to fabricate the multiscale-structured elast

Designing softness into robots holds great potential for augmenting robotic compliance in dynamic, unstructured environments. However, despite the body's softness, existing models mostly carry inherent hardness in their driving parts, such as pressure-regulating components and rigid circuit boards. This compliance gap can frequently interfere with the robot motion and makes soft robotic design dependent on rigid assembly of each robot component. We present a skin-like electronic system that enab

Development of highly sensitive pressure sensors that function well even in bending environments and operate at ultralow voltage is desirable for wearable applications. Here, a highly sensitive and bendable capacitive pressure sensor with the ability to distinguish pressure and bending stimuli and a pressure‐sensitive transistor (PST) that can be easily integrated into wearable sensor system due to ultralow voltage (as low as 1 V for stable signal detection) operation is demonstrated. By introdu

We report the formation of lateral-crack-free silver electrodes on highly pre-stretched poly(dimethylsiloxane) (PDMS) substrates using the inkjet-printing method followed by an annealing process under the pre-stretched state. Due to Poisson's effect, cracks are easily obtained in the direction lateral to the pre-stretching and releasing directions when the highly pre-stretched substrate is released after the electrode formation. In our method, however, Poisson's effect is suppressed significantl

High-performance all-inkjet-printed organic inverters are fabricated on flexible substrates. By introducing end-functionalized polystyrene on both surfaces of inkjet-printed source/drain Ag electrodes and poly(4-vinylphenol) dielectrics, organic-compatible and hydroxyl-free interfaces between those layers and 6,13-bis(triisopropylsilylethynyl)pentacene drastically reduce the interfacial trap and contact resistance. The resulting organic inverters show a full up-down switching performance and a h

A novel property of the negatively strain-dependent electrical resistance change of nickel conductive composites is presented. The composite shows negatively strain-dependent resistance change when magnetically arranged, while most conductive materials show opposite behavior. This negative dependency is utilized to produce highly stretchable electrodes and to demonstrate a new conceptual resolution-sustainable stretchable lighting/display device.

Abstract A stretchable display would be the ultimate form factor for the next generation of displays beyond the curved and foldable configurations that have enabled the commercialization of deformable electronic applications. However, because conventional active devices are very brittle and vulnerable to mechanical deformation, appropriate strategies must be developed from the material and structural points of view to achieve the desired mechanical stretchability without compromising electrical

Abstract Inkjet and transfer printing processes are combined to easily form patterned poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films as top anodes of all solution–processed inverted polymer light emitting diodes (PLEDs) on rigid glass and flexible plastic substrates. An adhesive PEDOT:PSS ink is formulated and fully customizable patterns are obtained using the inkjet printing process. In order to transfer the patterned PEDOT:PSS films, adhesion properties at interfaces

Soft features in electronic devices have provided an opportunity of gleaning a wide spectrum of intimate biosignals. Lack of data processing tools in a soft form, however, proclaims the need of bulky wires or low‐performance near‐field communication externally linked to a “rigid” processor board, thus tarnishing the true meaning of “soft” electronics. Furthermore, although of rising interest in stretchable hybrid electronics, lack of consideration in multilayer, miniaturized design and system‐le

Stretchable hybrid electronics (SHE) that combine high-performance rigid electronic devices with stretchable interconnects offer a facile route for accessing and processing bio-signals and human interactions. Incorporated with sensors and wireless communications, SHE achieves novel applications such as biomedical diagnosis, skin prosthetics, and robotic skin. The implementation of reliable SHE requires the comprehensive development of stretchable electrodes, bonding techniques, and strain-engine

Precise monitoring of human body signals can be achieved by soft, conformal contact and precise arrangement of wearable devices to the desired body positions. So far, no design and fabrication methodology in soft wearable devices is able to address the variations in the form factor of the human body such as the various sizes and shapes of individual body parts, which can significantly cause misalignments and the corresponding inaccurate monitoring. Here, a concept of soft modular electronic bloc

Abstract Liquid metals (LMs) are a special case of metals that exist in a liquid at room temperature, making them one of the most attractive conductive materials in stretchable electronics. In many cases, however, the LM attacks other metals in contact with the LM through penetration, embrittlement, and alloying. To address these critical issues, there have been efforts to introduce robust barriers, which can preserve the underlying metals without degradation. For example, graphene is employed a

The realization of large-area electronics with full integration of 1D thread-like devices may open up a new era for ultraflexible and human adaptable electronic systems because of their potential advantages in demonstrating scalable complex circuitry by a simply integrated weaving technology. More importantly, the thread-like fiber electronic devices can be achieved using a simple reel-to-reel process, which is strongly required for low-cost and scalable manufacturing technology. Here, high-perf

We investigated the hump characteristics of amorphous indium–gallium–zinc oxide thin-film transistors. The device showed a field effect mobility of 24.3 cm2 V−1 s−1, a threshold voltage (Vth) of 4.8 V, and a subthreshold swing of 120 mV/dec. Under positive gate bias stress, Vth showed bidirectional shift with a hump. Vth was positively and negatively shifted in the above-threshold and subthreshold regions, respectively. At high temperatures, Vth was more positively shifted without bidirectional

Abstract Silver nanowires (AgNWs) have been considered as replacements of indium tin oxide (ITO) due to superior optoelectronic properties and mechanical stability for flexible electronics. However, high cost and process complexity of patterning process disturb their applicability to commercial products. Herein, a facile patterning method of AgNWs by using inkjet‐printed conductive polymer templates is developed, which can be applied on various surfaces including super hydrophobic light‐emitting