Auxetic metamaterial inspired by the seesaw motion

Abstract

A mechanical metamaterial has been constructed using a network of interconnected isosceles triangles and right triangles by inspiration from the seesaw motion. The connections are defined as hinges with rotationally elastic restraints wherein each isosceles triangle is three neighboring rotating units while each right triangle is connected to four neighboring rotating units. The effective Poisson's ratio under on-axes loading were established using geometrical approach while the on-axes Young's moduli were developed by matching the spring rotational energy at the hinges of the metamaterial during relative rotation of the rigid units with the strain energy of deformation of the homogenized continuum. Results reveal that by adjusting the geometrical parameters, the Poisson's ratio can range from positive to negative values. The results also show that both the Poisson's ratio and Young's moduli have a wide range of geometrical parameters for fine tuning at low mechanical properties and well as a narrow range of geometrical parameters for coarse tuning at high mechanical properties. These observations suggest that the metamaterial has a wide range of applications from soft robotics to structural applications by adjustment of its geometrical parameters.