Variable-stiffness metamaterials with switchable Poisson’s ratio

Mechanical metamaterials are structured materials designed to exhibit unconventional mechanical responses. Most mechanical metamaterials have a single material response, but the ability to tune the intensity of a programmed response is useful to enhance the adaptability of the metamaterials to varying application requirements. This work presents variable-stiffness metamaterials (VSMMs) made from a thermally responsive, variable-stiffness Field's metal-silicone composite embedded in a soft silicone elastomer. We investigate VSMMs with different metamaterial structures and constituent material stiffness ratios, and we demonstrate that the VSMM properties are dominated by the embedded metamaterial in a stiff state and the host elastomer in a soft state. We showcase the utility of the VSMM by producing capacitive sensors that can switch between property states: high measurement sensitivity with limited deformations (60%).