Liquid-metal embedded sponge-typed triboelectric nanogenerator for omnidirectionally detectable self-powered motion sensor

With the increasing number of devices that require electrical energy, various types of triboelectric nanogenerators (TENGs), a promising technology for energy harvesting, have been developed in recent years. However, conventional TENGs show relatively low mechanical flexibility because each layer of the conventional TENGs is composed of rigid materials. Low mechanical flexibility produces electrical energy in one-way operation and limits the utilization of TENGs in a variety of applications. In this work, we develop the liquid-metal embedded sponge-typed TENG (LMST). Liquid-metal and silicon rubber are utilized to fabricate the LMST with a peculiar sponge shape, which is inherently including the randomly distributed pores with dispersed liquid-metal droplets. Hence, the LMST can be bent 180 degrees and stretched 300%, which indicates the great flexibility and stretchability of the LMST. The LMST with size of the 1.5 cm x 1.5 cm x 1.5 cm generated a short-circuit current (ISC) of 188 nA and an open-circuit voltage (VOC) of 24 V. Also, the 2.48 W/m2 of power density is generated from the proposed LMST by simply inserting wires into the LMST without any conventional processes for fabricating electrodes. Interestingly, the electrical power can be used simply by connecting wires to the LMS, and power can be greatly improved by increasing the number of wires connected to the LMST. Additionally, various shapes of the LMST are facilely designed using 3D printing technology for a wide spectrum of applications. To prove the applicability of the LMST with the unique porous structure, three types of self-powered sensor systems are demonstrated, which are detecting the pressure, the direction of a spinning ball, and real-time detecting malfunction of motor faults. The flexible advantages of the liquid-metal embedded sponge structure triboelectric nanogenerator device, allow us to extend its applicability to battery-free sensors that can be used in various locations.

Automated summary

The liquid-metal embedded sponge-typed TENG (LMST) exhibits high flexibility and stretchability, allowing for versatile applications and high power density output. By connecting wires, the LMST provides convenient electrical power supply and can enhance power by increasing the number of wires connected.