To keep pace with the rapid development of portable electronic devices, the demand for stable batteries with enhanced electrical capacities is also growing rapidly, but such demands are not easily met. Thus, energy-harvesting technology is an alternate solution, in which unintentionally abandoned energy is scavenged to supply electricity to portable electronics. Given that motion associated with daily human activities can involve large amounts of reusable energy, biomechanical energy harvesting has received significant research attention. [10][11][12][13][14][15][16][17][18] Several portable biomechanical energy-harvesting platforms are available based on piezoelectric, electromagnetic, and triboelectric effects. They offer the promise of generating electricity for standalone electronics without the need for external wiring.Triboelectric energy harvesting, which is based on the combination of contact electrification between two different material surfaces and electrical induction, has been spotlighted as a promising technology due to material selection diversity, high efficiency, and shape adaptability. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Previous studies of triboelectric energy harvesters, also known as triboelectric nanogenerators (TENGs), have found that the only requirement for generating electricity through a TENG is sequential contact and separation of two different material surfaces, making the TENG a promising portable energy-harvesting platform. [35][36][37][38][39][40][41][42][43][44][45][46] In addition, the advantageous characteristics of the TENG enable it to be used for self-powered sensing applications. [47][48][49][50] The operating principle of a TENG is based on the presence of charges on the surface of the material rather than its volume, so the volumetric power density has the potential to be improved far more than is the case with other energy-harvesting platforms. So far, the most widely and frequently used method to increase the output power is to introduce micro/nanoscale topography on the surface of the TENG to generate a large amount of electrical charges during its operation. In addition to modification of the contact surface, intentional control of the kinematics of the contact layer movement by using mechanical components can improve performance substantially. Given that almost all biomechanical energy has the rare characteristics A triboelectric nanogenerator (TENG) is a promising energy harvester that exploits the combination of contact electrification between two different material surfaces and electrical induction. In this study, a handheld-TENG (HH-TENG) is developed to harvest biomechanical energy effectively, especially energy generated from finger motions, which is one of the most common body movements involving lots of energy. To enhance the electrical output performance of the device while minimizing the inconvenience caused by carrying it, a rationally designed lightweight power transmission unit is adopted. As a result, an extremely high number...

In article number 2000003, Sung Jea Park, Dongwhi Choi and co‐workers present the development of a high‐performance handheld triboelectric nanogenerator (TENG). With adoption of a rationally designed lightweight mechanical power transmission unit, the simple finger pressing motion generates dramatically enhanced electrical output performance from the TENG and thus, it can be utilized as a potential portable power source for powering portable electronics without spatiotemporal limitation.