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 second in water. The voltage and current generated ex vivo by ultrasound energy transfer reached 2.4 volts and 156 microamps under porcine tissue. These findings show that a capacitive triboelectric electret is the first technology able to compete with piezoelectricity to harvest ultrasound in vivo and to power medical implants.

Here micropatterned poly(vinylidenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)) films‐based piezoelectric nanogenerators (PNGs) with high power‐generating performance for highly sensitive self‐powered pressure sensors are demonstrated. The microstructured P(VDF‐TrFE)‐based PNGs reveal nearly five times larger power output compared to a flat film‐based PNG. The micropatterning of P(VDF‐TrFE) polymer makes itself ultrasensitive in response to mechanical deformation. The application is demonstrated successfully as self‐powered pressure sensors in which mechanical energy comes from water droplet and wind. The mechanism of the high performance is intensively discussed and illustrated in terms of strain developed in the flat and micropatterned P(VDF‐TrFE) films. The impact derived from the patterning on the output performance is studied in term of effective pressure using COMSOL multiphysics software.

systems and makes them inconvenient for users. [9][10][11] In addition, the periodic exchange of the primary battery causes an enormous waste of resources and complex maintenance problems. [12][13][14] Although the ultralow power consumption system and the high capacity battery can extend the WSN system's operation time, it cannot ensure continuous operation of the system for decades. [15] Thus, an energy harvesting system that converts wasted ambient environment energy into valuable electric energy is one of the important technologies for a future sustainable society. [16][17][18] There are various energy harvesting systems, such as piezoelectric, [19][20][21][22] triboelectric, [23][24][25] thermoelectric, [26][27][28][29][30][31] pyroelectric, [32][33][34] photovoltaic, [35][36][37] and water evaporation-based energy harvesting systems [38,39] and those using green energy sources such as solar, wind, wave, heat, and vibrations. These renewable energy harvesting systems have been receiving great attention in the field of research into renewable and sustainable energy harvesters (EHs) to realize self-powering smart WSN systems and self-charging electronics. [40][41][42][43][44][45][46] The output performance of energy harvesting systems has rapidly improved, and WSN systems and energy harvesting systems have been combined. These two advancements have resulted in extend operation times of small electronic devices. Specialized EH, which uses one kind of green energy, is efficiently converting energy, but this system is fatally flawed because it is influenced by weather conditions. For example, biomechanical energy-based harvesters can generate energy both indoor and outdoors, but specific targeted biomechanical movement is required. [47] Thus, unexpected mechanical energy or other thermal and solar energy is wasted. Similarly, solar EHs can effectively harvest energy under illumination from the sun, but constantly changing weather conditions place constraints on solar cell performance. [48] Furthermore, thermal energy generated by mechanical energy or solar energy is wasted without additional thermal EHs. [49] Therefore, to prevent the useless wasting of energy by a single energy harvesting system, utilizing plural green energy harvesting systems is a countermeasure for sustainable energy harvesting, so that otherwise wasted energy is fully utilized with high energy conversion efficiency, which can power WSN systems at anytime, anywhere.Nature and artificial energies, such as solar, wind, wave, heat, machine vibration, automobile noise continuously exist, so 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 ...

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.

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 material is reported. The nanocomposite material consists of a high dielectric ceramic material, barium titanate, showing great charge‐trapping capability, together with a ferroelectric copolymer matrix, Poly(vinylidenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)), with electrically manipulated polarization with strong triboelectric charge transfer characteristics. Based on a contact potential difference study showing that poled P(VDF‐TrFE) has 18 times higher charge attracting properties, a fraction between two components is optimized. Boosting power‐generating performance is achieved for 1130 V of output voltage and 1.5 mA of output current with this ferroelectric composite‐based TNG, under 6 kgf of pushing force at 5 Hz. An enormously faster charging property than traditional polymer film‐based TNGs is demonstrated in this study. Finally, the charging of a self‐powering smartwatch with a charging management circuit system with no external power sources is demonstrated successfully.