Flexible pressure sensing film based on ultra-sensitive SWCNT/PDMS spheres for monitoring human pulse signals

Abstract

Flexible pressure sensors are essential components of electronic skins for future attractive applications ranging from human healthcare monitoring to biomedical diagnostics to robotic skins to prosthetic limbs. Here, we report a new kind of flexible pressure sensing film based on ultrasensitive single wall carbon nanotube (SWCNT)/polydimethylsiloxane (PDMS) spheres. These spheres with the diameter of 600 ± 20 μm were prepared using the dipping method, and were further sandwiched by flexible electrodes using a stack of double-sided tape. The sensing mechanism of this device was analyzed by classic thin plate theory for circular plate deflection. Its sensitivity was further optimized by the synthesis of sensitive materials and geometrical design of device parameters. Ultimately, the developed sensing film exhibited a maximum sensitivity of 46.7% kPa⁻¹ to resistance, great durability over 15 000 cycles, and very rapid mechanical responses (a few milliseconds). We also demonstrated that our sensing film can be used to detect the location and distribution of finger pressure, as well as to map the fingertip pulse signals, jugular venous pulse (JVP) signals and wrist pulse signals of the testers of different ages effectively.