Dukhyun Choi

Fully rollable transparent nanogenerators have been developed using chemical vapor deposition-grown large-scale graphene sheets as transparent electrodes and piezoelectric ZnO-nanorod arrays. The electrical and structural stability of the nanogenerators with excellent charge scavenging performance under external mechanical loads such as bending and rolling shows that graphene-based nanogenerators are suitable for self-powered rollable transparent device applications. Detailed facts of importance

Non-lithographic fabrication of a self-aligned nanopore SERS array with large-area hexagonal symmetry is achieved by Au deposition on an anodized aluminum oxide (AAO) template. Precise self-formation of plasmonic nanopore arrays with facile structural tunability allows control of the SERS response, and results in highly reproducible, uniform, and sensitive SERS with an enhancement factor of 107. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such do

The abundance of water on earth provides a large window to utilize the mechanical energy within river currents and ocean waves. In this regard, hydropower harvesting through solid-liquid contact electrification has received considerable interest in the recent past. Despite advancements in nanotechnology, liquid energy harvesting devices, especially solid-liquid triboelectric nanogenerators (S-L TENGs), require efficient engineering of the interfacial properties of their substrates to transfer li

Abstract In this work, we demonstrate the mode transition of charge generation between direct‐current (DC) and alternating‐current (AC) from transparent flexible (TF) piezoelectric nanogenerators (NGs), which is dependent solely on the morphology of zinc oxide (ZnO) nanorods without any use of an AC/DC converter. Tilted ZnO nanorods grown on a relatively low‐density seed layer generate DC‐type piezoelectric charges under a pushing load, whereas vertically aligned ZnO nanorods on a relatively hig

Self-powered triboelectric microfluidic system was developed for the simple and rapid liquid sensing with multiple methods such as triboelectric signal and resistance measurement.

Layer-by-layer multilayers are demonstrated for low-cost, durable, scalable, and wearable graphene-TENGs on flat or undulated polymer substrates and fabric textiles.

In this paper, signal amplifications of surface-enhanced Raman scattering (SERS) are realized by an optofluidic compact disc (CD)-based preconcentration method for effective label-free environmental and biomolecular detections. The preconcentration of target molecules is accomplished through the accumulation of adsorbed molecules on SERS-active sites by repeating a 'filling-drying' cycle of the assay solution in the optofluidic CD platform. After 30 cycles, the clear and high SERS signal of rhod

Triboelectric nanogenerators (TENGs) are used as self-power sources for various types of devices by converting external waves, wind, or other mechanical energies into electric power. However, obtaining a high-output performance is still of major concern for many applications. In this study, to enhance the output performance of polydimethylsiloxane (PDMS)-based TENGs, highly dielectric TiO_2-x nanoparticles (NPs) were embedded as a function of weight ratio. TiO_2-x NPs embedde

We have investigated a nanoscale networked single-walled carbon-nanotube (SWCNT) electrode as a top cathode electrode of transparent flexible (TF) nanogenerators, so as to improve the energy scavenging performance and the system stability. The morphological effect and the electrical stability of SWCNT films for TF nanogenerators are investigated. It is found that SWCNT films have a nanosized network surface with pores, exceeding 100 nm in size, which favor ZnO nanorods contacting the CNT electro

Abstract Mechanical energy scavengers convert irregular input mechanical energy into irregular electrical output. There is a need to enable uniform and predictable electric output from energy scavengers regardless of the variability in the mechanical input. So, in this work, a mechanical frequency regulator is proposed that fixes the input forces and input frequency acting on a triboelectric nanogenerator, thus enabling predictable electric output. The irregular low frequency mechanical input en

Abstract Most mechanical energy harvesters produce only small amounts of electrical power from extremely low‐frequency input motions and immediately stop generating electricity when mechanical kinetic energy is exhausted. Here, a steady, long‐lasting and power‐boosted triboelectric nanogenerator is reported that can efficiently harvest from extremely low‐frequency irregular motions of less than 0.1 Hz by utilizing an escapement mechanism and frequency up‐conversion device. The escapement mechani