Compressible sliver nanowires/polyurethane sponge metacomposites with weakly negative permittivity controlled by elastic deformation

Flexible and compressible metacomposites with negative permittivity have a great value in wearable devices, sensors, electronic skin, etc. To balance the negative permittivity behavior and flexibility, a novel preparation strategy was proposed in this study. The polyurethane sponge (PUS) was impregnated with synthesized sliver nanowires (AgNWs) to achieve flexible AgNWs/PUS composites, and the effect of compressed elastic deformation on negative permittivity was investigated. For the composites with 3.1 wt% AgNWs, when the compressed elastic deformation reached 60%, the permittivity changed from positive to negative values, conforming to Lorentz-like negative permittivity. When the content of AgNWs reached 6.3 wt%, the Drude-like negative permittivity began to appear without the action of an applied load, and the negative permittivity was as small as about − 2, indicating a weakly negative permittivity. Meanwhile, with the increase in deformation, the absolute values of Drude-like negative permittivity increased owing to the improvement of electron density. It manifested that the compressed elastic deformation played an important role in negative permittivity. Further investigation revealed that the inductive character was responsible for the negative permittivity. This paper provides a novel approach to controlling the negative permittivity according to elastic deformation.