Semi-open discrete mechanical metamaterials and application in robotics

Abstract

Mechanical metamaterials (MMs) are gradually noticed and studied by researchers due to their unique properties, whose practical application however is significantly restricted because traditional manufacturing methods are mainly concentrated in the micro field. Some researchers propose designing and applying mechanical metamaterials based on discrete voxels in order to reduce the gap in MMs between study and application. In particular, MIT presents four voxels that systematically summarize the discrete concept. However, the stiffness and strength of voxels are bounded because of the open-cell or closed-cell structures, which is also challenging to balance the mass and space utilization. In this paper, we integrate both structures and propose three novel semi-open voxels with anisotropy properties that enhance stiffness and strength for macro application and improve the space utilization efficiency while maintaining low mass. In addition, voxels are assembled in the robot field based on digital material concepts. Specifically, the macroscopic system is extended by multiple units or cells simulating continuous material properties. Three semi-open voxels, the unit of MMs, are proposed for the first time and split as internal and external elements to decouple complex physical properties. Besides, the Response Surface method is employed to optimize the parameters for superior mechanical performance, and then the elastic modulus between numerical simulation and bulking experiments with optimized value is compared. Further, a vehicle is assembled discretely with voxels and access to the advantage of load capacity, providing a feasible alternative to integrating MMs in robotics in the future.