Highly Sensitive Flexible Sensors for Human Activity Monitoring and Personal Healthcare

Flexible sensors are capable of converting multiple human physiological signals into electrical signals for various applications in clinical diagnostics, athletics, and human-machine interaction. High-performance flexible strain sensors are particularly desirable for sensitive, reliable, and long-term monitoring, but current applications are still constrained due to high response threshold, low recoverability properties, and complex preparation methods. In this study, we present a stable and flexible strain sensor by a cost-effective self-assemble approach that demonstrates remarkable sensitivity (2169), ultrafast response and recovery time (112 ms), and wide dynamic response range (0-50%), as confirmed in human pulse and human-computer interaction. These excellent performances can be attributed to the design of a Polydimethylsiloxane (PDMS) substrate integrated with multiwalled carbon nanotubes (MWCNT) and graphene nanosheets (GNFs), which results in high electrical conductivity. The MWCNT serves as a bridge, connecting the GNFs to create an efficient conductive path even under a strain of 50%. We also demonstrate the strain sensor's capability in weak physiological signal pulse measurement and excellent resistance to mechanical fatigue. Moreover, the sensor shows diverse sensitivities in various tensile states with different signal patterns, making it highly suitable for full-range human monitoring and flexible wearable systems.