Expandable microsphere-based triboelectric nanogenerators as ultrasensitive pressure sensors for respiratory and pulse monitoring

Physiological monitoring sensors have attracted increasing research interest due to their broad application potential in daily activities, sports performance and health status monitoring for next generation athletic/clinical technologies. Having high sensitivity and low power consumption are essential to realize these applications in advanced portable/remote forms. In this work, triboelectric nanogenerators (TENGs), which are based on expandable microspheres in a polydimethylsiloxane (PDMS) mixture, were constructed as self-powered pressure sensors with ultrahigh sensitivity for biological signal monitoring through a low-cost and simple processing technique. Different sensitivities can be obtained by adjusting the weight percentage of microspheres in the PDMS, and the output voltage of the sensor was analyzed by a theoretical model, which was consistent with the simulation results. The maximum sensitivity of the sensor can reach 150 mV/Pa so respiratory and pulse monitoring can be implemented by attaching the ultrasensitive pressure sensor to the chest and wrist of a human body, respectively.