Recyclable flexible sensors based on digital-light-processing 3D printing of a thermoplastic elastomer and facile transfer of pencil-marked graphite films

Light-based 3D printing has revolutionized the development of flexible strain sensors by enabling the customizable fabrication of geometrically complex structures with high precision. A recyclable elastomer substrate for strain sensors based on photocuring 3D printing is highly desirable from ecological and economic perspectives. However, it is hard to achieve both printability and recyclability simultaneously since crosslinked polymer networks are difficult to reprocess. In this study, in order to recycle the digital-light-processing (DLP)-3D-printed sensor elastomer, a design strategy for fabricating stretchable strain sensors was proposed by combining direct DLP-3D-printing of a thermoplastic poly(isodecyl acrylate)(PIDA)/poly(styrene-b-ethylene-butylene-b-styrene)(SEBS) elastomer and transferring a conductive layer of pencil-marked graphite films onto it. The photoresin for printing was prepared by dissolving commercial thermoplastic elastomer SEBS in monomer IDA without any crosslinker. Attributed to the linear polymer molecular structure and the good mechanical properties of SEBS, the photocured elastomer showed good thermoplasticity and elasticity. The PIDA/SEBS sensor has a wide sensing range (strain: 0-280%) with high sensitivity (gauge factor: 9355). The 3D printed finger sleeve sensor can monitor the movement of finger bending precisely. By erasing the conductive pencil marks, the PIDA/SEBS elastomer can be remolded to prepare a new strain sensor.