Seung Hwan Ko

A highly stretchable metal electrode is developed via the solution-processing of very long (>100 μm) metallic nanowires and subsequent percolation network formation via low-temperature nanowelding. The stretchable metal electrode from very long metal nanowires demonstrated high electrical conductivity (∼9 ohm sq−1) and mechanical compliance (strain > 460%) at the same time. This method is expected to overcome the performance limitation of the current stretchable electronics such as graphene, car

In this paper, in order to increase the power conversion efficiency we demonstrated the selective growth of "nanoforest" composed of high density, long branched "treelike" multigeneration hierarchical ZnO nanowire photoanodes. The overall light-conversion efficiency of the branched ZnO nanowire DSSCs was almost 5 times higher than the efficiency of DSSCs constructed by upstanding ZnO nanowires. The efficiency increase is due to greatly enhanced surface area for higher dye loading and light harve

A highly stretchable and transparent electrical heater is demonstrated by constructing a partially embedded silver nanowire percolative network on an elastic substrate. The stretchable network heater is applied on human wrists under real-time strain, bending, and twisting, and has potential for lightweight, biocompatible, and versatile wearable applications. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer revi

All-printed electronics is the key technology to ultra-low-cost, large-area electronics. As a critical step in this direction, we demonstrate that laser sintering of inkjet-printed metal nanoparticles enables low-temperature metal deposition as well as high-resolution patterning to overcome the resolution limitation of the current inkjet direct writing processes. To demonstrate this process combined with the implementation of air-stable carboxylate-functionalized polythiophenes, high-resolution

The future electronics will be soft, flexible and even stretchable to be more human friendly in the form of wearable computers. However, conventional electronic materials are usually brittle. Recently, carbon based materials are intensively investigated as a good candidate for flexible electronics but with limited mechanical and electrical performances. Metal is still the best material for electronics with great electrical properties but with poor transparency and mechanical performance. Here we

To overcome the limitation of the conventional single axis-strain sensor, we demonstrate a multidimensional strain sensor composed of two layers of prestrained silver nanowire percolation network with decoupled and polarized electrical response in principal and perpendicular directional strain. The information on strain vector is successfully measured up to 35% maximum strain with large gauge factor (>20). The potential of the proposed sensor as a versatile wearable device has been further confi

Abstract As an alternative to the brittle and expensive indium tin oxide (ITO) transparent conductor, a very simple, room‐temperature nanosoldering method of Ag nanowire percolation network is developed with conducting polymer to demonstrate highly flexible and even stretchable transparent conductors. The drying conducting polymer on Ag nanowire percolation network is used as a nanosoldering material inducing strong capillary‐force‐assisted stiction of the nanowires to other nanowires or to the

A facile fast laser nanoscale welding process uses the plasmonic effect at a nanowire (NW) junction to suppress oxidation and successfully fabricate a Cu-NW-based percolation-network conductor. The "nanowelding" process does not require an inert or vacuum environment. Due to the low-temperature and fast-process nature, plasmonic laser nanowelding may form Cu-nanowire networks on heat-sensitive, flexible or even stretchable substrates.

Accurate temperature field measurement provides critical information in many scientific problems. Herein, a new paradigm for highly sensitive, flexible, negative temperature coefficient (NTC) thermistor-based artificial skin is reported, with the highest temperature sensing ability reported to date among previously reported NTC thermistors. This artificial skin is achieved through the development of a novel monolithic laser-induced reductive sintering scheme and unique monolithic structures. The

We introduce a facile approach to fabricate a metallic grid transparent conductor on a flexible substrate using selective laser sintering of metal nanoparticle ink. The metallic grid transparent conductors with high transmittance (>85%) and low sheet resistance (30 Ω/sq) are readily produced on glass and polymer substrates at large scale without any vacuum or high-temperature environment. Being a maskless direct writing method, the shape and the parameters of the grid can be easily changed by CA

Recent research progress of relieving discomfort between electronics and human body involves serpentine designs, ultrathin films, and extraordinary properties of nanomaterials. However, these strategies addressed thus far each face own limitation for achieving desired form of electronic-skin applications. Evenly matched mechanical properties anywhere on the body and imperceptibility of electronics are two essentially required characteristics for future electronic-skin (E-skin) devices. Yet accom

A hyper-stretchable and deformable elastic-composite generator is developed using a piezoelectric nanocomposite composed of (1−x){Pb(Mg1/3Nb2/3)O3}–x{PbTiO3} microparticles, carbon nanotubes, a silicone rubber matrix, and very long silver (Ag) nanowire percolation network electrodes. To date, this nanogenerator sets world records for output performance, strain capacity, mechanical stability, and commercial feasibility in the research field for stretchable and deformable piezoelectric energy harv

As is frequently seen in sci‐fi movies, future electronics are expected to ultimately be in the form of wearable electronics. To realize wearable electronics, the electric components should be soft, flexible, and even stretchable to be human‐friendly. An important step is presented toward realization of wearable electronics by developing a hierarchical multiscale hybrid nanocomposite for highly flexible, stretchable, or transparent conductors. The hybrid nanocomposite combines the enhanced mecha

Future electronics are expected to develop into wearable forms, and an adequate stretchability is required for the forthcoming wearable electronics considering various motions occurring in human body. Along with stretchability, transparency can increase both the functionality and esthetic features in future wearable electronics. In this study, we demonstrate, for the first time, a highly stretchable and transparent electromagnetic interference shielding layer for wearable electronic applications

One-step direct nanoimprinting of metal nanoparticles was investigated to fabricate nano-/microscale metallic structures such as nanodot and nanowire arrays. This was done at low temperatures and pressures, utilizing the low melting temperature and viscosity of metal nanoparticle solutions. Through precise control of the fluidic properties of the nanoparticle solution and the mold design, high-quality nanoscale features with no or negligible residual layer were nanoimprinted. Nanoscale electroni