Design and evaluation of 3D-printed auxetic structures coated by CWPU/graphene as strain sensor.

A strain sensor characterized by elasticity has recently been studied in various ways to be applied to monitoring humans or robots. Here, 4 types of 3D-printed auxetic lattice structures using thermoplastic polyurethane as raw material were characterized: truss and honeycomb with positive Poisson's ratio and chiral truss and re-entrant with negative Poisson's ratio. Each structure was fabricated as a flexible and stable strain sensor by coating graphene through a dip-coating process. The fabricated auxetic structures have excellent strength, flexibility, and electrical conductivity desirable for a strain sensor and detect a constant change in resistance at a given strain. The 3D-printed auxetic lattice 4 type structures coated with CWPU/Graphene suggest potential applications of multifunctional strain sensors under deformation.