A breathable, sensitive and wearable piezoresistive sensor based on hierarchical micro-porous PU@CNT films for long-term health monitoring

Creating highly sensitive and comfortable flexible sensors remain a key challenge in the development of electronic-skin. A breathable, sensitive and long-term wearable piezoresistive sensor based on hierarchical micro-porous PU@CNT films and a single-sided electrode were prepared by simple and effective methods. Distilled water is used as a non-solvent to induce the separation of films polyurethane (PU) to create the hierarchical porous structures. The micro-computed tomography is used to quantitatively analyze the 3D structure of the porous films with different PU concentration, which is, a small pore volume of less than 50 mu m(3) occupy the majority, the porosities are from 64.25% to 40.27%, and the surface areas are of 5.6 x 10(6) to 12.0 x 10(6) mu m(2). Such micro-porous structures performs the air and moisture permeability of the PU@CNT films and the sensors which are more than 8 times that of non-porous film, and effectively improves the sensitivity of the sensors to 51.53 kPa(-1). The hysteresis error of the porous PU@CNT sensor which possesses a higher specific surface area and lower porosity is optimized by 67.8% and it has high stability (>8000 cycles). Finally, the sensors were successfully to detecting article pulse waves, throat and finger movements, and spatially resolved pressure.