Recent Progress in Self-Powered Sensors Based on Liquid–Solid Triboelectric Nanogenerators

Recently, there has been a growing need for sensors that can operate autonomously without requiring an external power source. This is especially important in applications where conventional power sources, such as batteries, are impractical or difficult to replace. Self-powered sensors have emerged as a promising solution to this challenge, offering a range of benefits such as low cost, high stability, and environmental friendliness. One of the most promising self-powered sensor technologies is the L–S TENG, which stands for liquid–solid triboelectric nanogenerator. This technology works by harnessing the mechanical energy generated by external stimuli such as pressure, touch, or vibration, and converting it into electrical energy that can be used to power sensors and other electronic devices. Therefore, self-powered sensors based on L–S TENGs—which provide numerous benefits such as rapid responses, portability, cost-effectiveness, and miniaturization—are critical for increasing living standards and optimizing industrial processes. In this review paper, the working principle with three basic modes is first briefly introduced. After that, the parameters that affect L–S TENGs are reviewed based on the properties of the liquid and solid phases. With different working principles, L–S TENGs have been used to design many structures that function as self-powered sensors for pressure/force change, liquid flow motion, concentration, and chemical detection or biochemical sensing. Moreover, the continuous output signal of a TENG plays an important role in the functioning of real-time sensors that is vital for the growth of the Internet of Things.