Ultra-sensitive, lightweight, and flexible composite sponges for stress sensors based combining of through-hole polyimide sponge and pleated stacked reduced graphene oxide

For the advantages of light weight, rapid recovery, and high sensitivity, the conductive flexible composite sponges with idiographic spatial structure as a stress sensor has received great attention. However, for small pressure and deformation, it is still challenging to achieve high sensitivity and response. Here, the polyimide (PI) sponge with through-hole structure and special functional groups is successfully fabricated through a clever structural design and is used as substrate of the composite sponges. The new PI sponge effectively induces the fabrication of reduced graphene oxide (RGO) sponge that possessing a pleated stacked structure in the cells only by a hydrothermal route. By controlling the GO dispersion concentration, the maximum electrical conductivity of the composite sponges reaches to 10.68 x 10-4 S/m. The maximum sensitivity of composite sponges arrives at 1.172 kPa-1 and possesses a wide response range from 0 to 1 kPa. Comparing with previous similar works, the maximum sensitivity is improved by 74.9-1231.8%. Meanwhile, composite sponges exhibit excellent cycling stability under different compression rates, and present obvious response to tiny stress or deformation which is as low as 0.09 N and 0.45%. This is of great significance for the application of the conductive composite sponges sensor in tiny stress.

Automated summary

A polyimide (PI) sponge with a through-hole structure and special functional groups was successfully fabricated, serving as the substrate for reduced graphene oxide (RGO) sponge used in conductive composite sponges. These sponges exhibited high sensitivity, wide response range, improved maximum sensitivity compared to previous works, and excellent cycling stability under different compression rates, making them ideal for tiny stress sensors.