Highly compressible piezoresistive strain sensor with a semi-IPN structure based on PU sponge/RTV silicone rubber/MWCNTs

Recently electrically conductive piezoresistive sensors with high deformability and compressibility based on nanostructured polymeric foams have attracted great attention. The presence of a rubbery phase inside the structure of these materials leads to a dramatic enhancement of flexibility and pressure sensitivity. In the present work, attempts have been made to fabricate a highly deformable and structural recoverable electrically conductive piezoresistive sponge as a strain sensor with a semi-interpenetrating network structure via the impregnation process of pre-fabricated polyurethane sponges into the doping solution composed of crosslinkable room temperature vulcanized silicone rubber (RTVSR) and multiwall carbon nanotubes (MWCNTs). Crosslinking of rubbery phase in conjunction with interconnected MWCNTs network resulted in outstanding properties. Excellent strain sensing (gauge factor value up to 3.71) and compressibility (decreasing 60% of compression set) were observed under compressive pressure as a result of the presence of a rubbery phase with an optimized elasticity. The obtained results implied the structure stability under cyclic deformations indicating strong intermolecular adhesion between MWCNTs and the rubbery phase.