A Liquid–Solid Contact Electrification Based All‐Optical Liquid Flow Sensor for Microfluidic Analysis in Biomedical Applications

Abstract Liquid flow sensor is an important component of the microfluidic system for analytical science and biomedical systems. However, traditional microfluidic systems are complex in structure, costly, bulky, and generate environmental pollutants. Herein, a novel and high‐performance self‐powered all‐optical liquid flow sensor (ALFS) based on triboelectrification‐induced electroluminescence (TIEL) is proposed. The TIEL signal is self‐generated in real time through contact electrification between a polymer–fluid–air surface and moving fluid. Moreover, the amplitude and time span of the electric field can be swiftly altered by adjusting the bottom grid electrode layer with an appropriate geometric design, so that a high sensitivity of 0.089 s mm –1 and an extremely low flow velocity limit of 1 mm s –1 can be achieved. The velocity, volume, and composition of the liquid flow can be obtained either by observation or through optical information extraction from data analysis software. Furthermore, the ALFS can be incorporated into an infusion monitor and a microfluidic chip for biomedical applications. This study proposes not only an innovative method for liquid flow monitoring but also a new rationale of coupling triboelectrification into the microfluidic system design, which potentially has a wide range of applications in the medical, biological, and industrial fields.