Freestanding silver/polypyrrole composite film for multifunctional sensor with biomimetic micropattern for physiological signals monitoring

Flexible electronic sensors, which can perceive and respond to mechanical stimuli, are essential components of wearable electronics. Here, the utilization of biomimetic microstructures from natural lotus leaves and freestanding polypyrrole/silver (PPy/Ag) hybrid films are demonstrated to design and fabricate multifunctional sensors. The sensors consist of sandwich structure, including the surface of the designed polydimethylsiloxane (PDMS) films with biomimetic micropattern and the interlayer of the conductive PPy/Ag film (PDMS/PPy/Ag/PDMS). It is discovered that the polypyrrole and silver nanoparticles (PPy/AgNPs) aggregated and the freestanding PPy/Ag hybrid film formed at the air/water interface under ultraviolet (UV) irradiation. The PPy/Ag film exhibits well electrical conductivity, which could be used for fabricating the sensors to detect pressures, stretching and bending forces. The sensors based on the micropatterned PDMS substrate show well strain gauge factor (≈21 for 18 ~ 20 strain) and pressure sensitivity (≈0.58 kPa−1 in 300 ~ 400 Pa) due to the effective contact areas. The sensors attract considerable attention for their application in monitoring finger pressure, respiration, acoustic vibrations, and real-time pulse wave at the current detection range from 0 to 60 mA. The results indicate that the PPy/Ag-based sensors with high sensitivity have promising potential for the future applications in wearable electronics and human-machine devices.