Jinsung Chun

Hydrophobic Sponge Structure-Based Triboelectric Nanogenerator

Hydrophobic sponge structure-based triboelectric nanogenerators using an inverse opal structured film for sustainable energy harvesting over a wide range of humid atmosphere have been successfully demonstrated. The output voltage and current density reach a record value of 130 V and 0.10 mA cm(-2) , respectively, giving over 10-fold power enhancement, compared with the flat film-based triboelectric nanogenerator.

Highly Stretchable 2D Fabrics for Wearable Triboelectric Nanogenerator under Harsh Environments

Highly stretchable 2D fabrics are prepared by weaving fibers for a fabric-structured triboelectric nanogenerator (FTENG). The fibers mainly consist of Al wires and polydimethylsiloxane (PDMS) tubes with a high-aspect-ratio nanotextured surface with vertically aligned nanowires. The fabrics were produced by interlacing the fibers, which was bonded to a waterproof fabric for all-weather use for fabric-structured triboelectric nanogenerator (FTENG). It showed a stable high-output voltage and current of 40 V and 210 μA, corresponding to an instantaneous power output of 4 mW. The FTENG also exhibits high robustness behavior even after 25% stretching, enough for use in smart clothing applications and other wearable electronics. For wearable applications, the nanogenerator was successfully demonstrated in applications of footstep-driven large-scale power mats during walking and power clothing attached to the elbow.

Mesoporous pores impregnated with Au nanoparticles as effective dielectrics for enhancing triboelectric nanogenerator performance in harsh environments

A facile and scalable synthesis of mesoporous films impregnated with Au nanoparticles (NPs) as effective dielectrics is demonstrated for enhancing the nanogenerator performance based on vertical contact-separation mode. This technique is so simple and scalable, providing a promising solution for developing large-scale and practical self-powered devices. The spatial distribution of Au NPs made it possible to fabricate an Au NP-embedded mesoporous triboelectric nanogenerator (AMTENG) with a high output power of 13 mW under cycled compressive force, giving over 5-fold power enhancement, compared with a flat film-based TENG under the same mechanical force. It is proposed that the presence of aligned dipoles produced due to the charges created by the contact between Au NPs and PDMS inside the pores can influence the surface potential energy of mesoporous films. With such an enhanced power output and unique device design, we demonstrate various applications such as self-powered shape mapping sensors, foot-step driven large-scale AMTENGs, and integrated circuits with capacitors for powering commercial cell phones for realizing self-powered systems from footsteps, wind power, and ocean waves.

Boosted output performance of triboelectric nanogenerator via electric double layer effect

For existing triboelectric nanogenerators (TENGs), it is important to explore unique methods to further enhance the output power under realistic environments to speed up their commercialization. We report here a practical TENG composed of three layers, in which the key layer, an electric double layer, is inserted between a top layer, made of Al/polydimethylsiloxane, and a bottom layer, made of Al. The efficient charge separation in the middle layer, based on Voltas electrophorus, results from sequential contact configuration of the TENG and direct electrical connection of the middle layer to the earth. A sustainable and enhanced output performance of 1.22 mA and 46.8 mW cm−2 under low frequency of 3 Hz is produced, giving over 16-fold enhancement in output power and corresponding to energy conversion efficiency of 22.4%. Finally, a portable power-supplying system, which provides enough d.c. power for charging a smart watch or phone battery, is also successfully developed.

Robust nanogenerators based on graft copolymers via control of dielectrics for remarkable output power enhancement

Robust nanogenerator based on poly(tert-butyl acrylate)–grafted PVDF copolymers via dielectric constant control is demonstrated. A robust nanogenerator based on poly(tert-butyl acrylate) (PtBA)–grafted polyvinylidene difluoride (PVDF) copolymers via dielectric constant control through an atom-transfer radical polymerization technique, which can markedly increase the output power, is demonstrated. The copolymer is mainly composed of α phases with enhanced dipole moments due to the π-bonding and polar characteristics of the ester functional groups in the PtBA, resulting in the increase of dielectric constant values by approximately twice, supported by Kelvin probe force microscopy measurements. This increase in the dielectric constant significantly increased the density of the charges that can be accumulated on the copolymer during physical contact. The nanogenerator generates output signals of 105 V and 25 μA/cm2, a 20-fold enhancement in output power, compared to pristine PVDF–based nanogenerator after tuning the surface potential using a poling method. The markedly enhanced output performance is quite stable and reliable in harsh mechanical environments due to the high flexibility of the films. On the basis of these results, a much faster charging characteristic is demonstrated in this study.