Metamaterial robot driven by nonlinear elastic waves with stop band and nonreciprocal crawling

Due to the special ability of wave manipulation, elastic wave metamaterials have many interesting applications in mechanical engineering, vibration and sound isolation. This work proposes a movable metamaterial driven by nonlinear elastic waves with stop band and nonreciprocal crawling. Inspired by stop band properties, the metamaterial employs a periodic structure of nonlinear diatomic chain. A defect mass is introduced near the wave source to break the periodicity and symmetry, which leads to the nonreciprocal propagation of nonlinear elastic waves. With the asymmetric friction, the nonreciprocal and one-directional crawling of the metamaterial can be observed, which behaves as a movable mechanical diode. Furthermore, theoretical analysis is performed to derive the band structure and crawling velocity, which are supported by experiments. This research wishes to introduce nonlinear elastic wave metamaterials into new designs of robotics.