Low hysteresis and high sensitivity TPU/carbonized wood cellulose sponge sensors for monitoring dynamic pulses.

The importance of continuous and reliable pulse wave monitoring is constantly being increased in health signal monitoring and disease diagnoses. Flexible pressure sensors with high sensitivity, low hysteresis and fast response time are an effective means for monitoring pulses. Herein, a special wave-shaped layered porous structure of carbonized wood cellulose sponge (CWCS) was constructed based on natural wood (NW). Thermoplastic polyurethane (TPU)/CWCS (PCWCS) composite flexible pressure sensitive elements were formed by immersing a TPU solution into the CWCS skeleton. The PCWCS-4 % based sensors exhibited high sensitivity of 164.77 kPa (0.01-0.5 kPa), low hysteresis (0.70 %), short response time (21 ms), low detection limit and good cycling stability. The exceptional sensing performance was attributed to the wave-shaped layered porous structure of the PCWCS, which rapidly established conductive pathways and reduced stress concentrations during compression. Due to the high sensitivity and low hysteresis of sensors, more comprehensive pulse and other physiological signals could be obtained. Therefore, the PCWCS flexible pressure sensor possesses great potential for application in smart wearable and healthcare.