High-sensitivity gradient porous ionic polymer pressure sensor in charge-sensing mode

Ionic polymers are composite materials consisting of polymer networks, solvents, and mobile ions, which can generate an electrical potential under external pressure. Existing research works have focused on enhancing the voltage response of the ionic polymer sensors, but it is usually difficult to exceed 100 mV. For the low impedance resulting from ionic conductivity properties and easy charge migration distribution, they may have high charge sensitivity. This Letter proposed an ionic polymer-based network of pressure sensors with gradient porous sensing structure, which is easily and quickly constructed, that has high sensitivity in the charge-sensing mode. The gradient porous structure is prepared layer by layer using NaCl as the porogen particles. The experimental results show that the gradient porous structure has exceptionally high charge sensitivity, reaching 5629 and 2147 pC/N in the range of 0-0.5 and 0.5-2.5 N, respectively, which is significantly better than those of the planar and surface micro-pyramid structures. Stress analysis is also carried out, and the simulation results show that the stress dramatically changes with the gradient of porosity, which significantly promotes the migration of cations and reveals the ultra-high charge response of this structure. The results can provide guidance for the design of the high-sensitivity ionic polymer pressure sensor.