Micro/nano-structure Skeleton Assembled with Graphene for Highly Sensitive and Flexible Wearable Sensor

Impregnated piezoresistive sensors based on polymer skeleton are advantageous in mechanical resilience and signal collection, but the large pore size of existing skeleton like polyurethane foams suppressed conductive contacts and hence limited the sensitivity. In this paper, a micro/nano-structure skeleton featured as three-dimension (3D) nanofiber was fabricated using environmental-friendly supercritical CO2 (scCO2) foaming. The reduced graphene oxide (rGO) was assembled on 3D ethylene-vinyl alcohol copolymer (EVOH) nanofibers, forming multi-conductive contacts, and a high-sensitivity rGO@EVOH flexible piezoresistive sensor was then obtained. The full processing of the sensor includes environmental-friendly scCO2 foaming and hydrothermal reduction. This high-performance sensor has ultra-high sensitivity of 130.9 kPa-1 in the low-pressure range of 1-5 kPa, which is 500 times higher than that of the sensors loaded with rGO on commercial open-cell foams. This work is a breakthrough for impregnated polymer skeleton sensor using 3D hydrophilic micro/nano-structure skeleton made by full green processing.