Sang‐Woo Kim

A major challenge for implantable medical systems is the inclusion or reliable delivery of electrical power. We use ultrasound to deliver mechanical energy through skin and liquids and demonstrate a thin implantable vibrating triboelectric generator able to effectively harvest it. The ultrasound can induce micrometer-scale displacement of a polymer thin membrane to generate electrical energy through contact electrification. We recharge a lithium-ion battery at a rate of 166 microcoulombs per sec

This research is concerned with the fungicidal properties of nano-size silver colloidal solution used as an agent for antifungal treatment of various plant pathogens. We used WA-CV-WA13B, WA-AT-WB13R, and WA-PR-WB13R silver nanoparticles (AgNPs) at concentrations of 10, 25, 50, and 100 ppm. Eighteen different plant pathogenic fungi were treated with these AgNPs on potato dextrose agar (PDA), malt extract agar, and corn meal agar plates. We calculated fungal inhibition in order to evaluate the an

Transparent flexible graphene triboelectric nanogenerators as new promising applications of chemical vapor deposition-grown graphene are successfully demonstrated. The work function and friction are decisive factors to understand the difference in output performance depending on the number of layers of graphene. In this work, we were able to power an LCD, LEDs, and an EL display using the electrical power output of the graphene triboelectric nanogenerator without any external energy source. As a

Recently, sustainable green energy harvesting systems have been receiving great attention for their potential use in self-powered smart wireless sensor network (WSN) systems. In particular, though the developed WSN systems are able to advance public good, very high and long-term budgets will be required in order to use them to supply electrical energy through temporary batteries or connecting power cables. This report summarizes recent significant progress in the development of hybrid nanogenera

Abstract The preparation of ferroelectric polymer–metallic nanowire composite nanofiber triboelectric layers is described for use in high‐performance triboelectric nanogenerators (TENGs). The electrospun polyvinylidene fluoride (PVDF)–silver nanowire (AgNW) composite and nylon nanofibers are utilized in the TENGs as the top and bottom triboelectric layers, respectively. The electrospinning process facilitates uniaxial stretching of the polymer chains, which enhances the formation of the highly o

Low output current represents a critical challenge that has interrupted the use of triboelectric nanogenerators (TNGs) in a wide range of applications as sustainable power sources. Many approaches (e.g., operation at high frequency, parallel stacks of individual devices, and hybridization with other energy harvesters) remain limited in solving the challenge of low output current from TNGs. Here, a nanocomposite material system having a superior surface charge density as a triboelectric active ma

Sound-driven power generation using nanogenerators based on piezoelectric ZnO nanowires has been demonstrated. Systematic investigations on the power-generating performance of sound-driven nanogenerators clearly support that the measured output voltage originated from the sound-driven nanogenerator. This study shows that sound can be one of promising energy sources when using highly efficient nanogenerators based on piezoelectric nanowires. Detailed facts of importance to specialist readers are

A piezopotential-powered active matrix strain sensor array based on a piezopotential-gated graphene transistor (GT) is demonstrated using a piezoelectric polymer. The strain sensor based on the piezopotential-gated GT exhibits excellent performance, including ultrahigh sensitivity (gauge factor = 389) and good durability (>3000 bending and releasing cycles) with a minimum detectable strain at 0.008%.

Self-powered implantable devices have the potential to extend device operation time inside the body and reduce the necessity for high-risk repeated surgery. Without the technological innovation of in vivo energy harvesters driven by biomechanical energy, energy harvesters are insufficient and inconvenient to power titanium-packaged implantable medical devices. Here, we report on a commercial coin battery-sized high-performance inertia-driven triboelectric nanogenerator (I-TENG) based on body mot

The extremely stable high‐power generation from hybrid piezoelectric nanogenerator (HP‐NG) based on a composite of single‐crystalline piezoelectric perovskite zinc stannate (ZnSnO 3 ) nanocubes and polydimethylsiloxane without any electrical poling treatment is reported. The HP‐NG generates large power output under only vertical compression, while there is negligible power generation with other configurations of applied strain, such as bending and folding. This unique high unidirectionality of p

In this study, we investigated the antifungal activity of three different forms of silver nanoparticles against the unidentified ambrosia fungus Raffaelea sp., which has been responsible for the mortality of a large number of oak trees in Korea. Growth of fungi in the presence of silver nanoparticles was significantly inhibited in a dosedependent manner. We also assessed the effectiveness of combining the different forms of nanoparticles. Microscopic observation revealed that silver nanoparticle

Graphene tribotronics is introduced for touch-sensing applications such as electronic skins and touch screens. The devices are based on a coplanar coupling of triboelectrification and current transport in graphene transistors. The touch sensors are ultrasensitive, fast, and stable. Furthermore, they are transparent and flexible, and can spatially map touch stimuli such as movement of a ball, multi-touch, etc.