Self-powered liquid triboelectric microfluidic sensor for pressure sensing and finger motion monitoring applications

Pressure sensors with flexibility are important functional components as the interface between the mechanical motion and electric signal in healthcare monitoring system. Conventional triboelectric based pressure sensors have advantages of simple structure configuration and self-powered sensing mechanism. However, the contact separation working principle requires macro-scale air gap and the performance is largely affected by the separation distance, which is not suitable for conformal human motion sensing. Hence in this paper, we report a flexible microfluidic pressure sensor based on liquid-solid interface triboelectrification when liquid flows in a microfluidic channel. The proposed microfluidic pressure sensor is able to have a conformal contact with human skin and no separation gap is required due to the microfluidic chamber and channel design. It is capable of working in two sensing mechanisms- triboelectric mechanism and capacitive mechanism. Triboelectric mechanism can be used to detect the dynamic pressure change on device without external power supply. Capacitive mechanism can be adopted as complementary sensing mechanism to detect both dynamic pressure change and static pressure. The proposed microfluidic pressure sensor can monitor both the magnitude and frequency of the pressure applied on the device simultaneously. Besides, the device can be integrated with microfluidic system as a self-powered flow rate sensor. Moreover, it can be conformally attached on human finger for finger bending degree and bending frequency detection. The proposed microfluidic pressure sensor offers more usage flexibility for flow rate, finger motion monitoring and the potentials for more complex human motion monitoring applications.