Passive Mechanical Metamaterial Sensor and Actuator

Abstract

In recent years, and with the continual development of additive manufacturing technologies, mechanical metamaterials have been explored for their programmable nature. This has opened a new design space into devices using functional materials. In this paper, a novel mechanical metamaterial device is designed, combining anisotropic 3D unit cells to slender beams. By controlling the separation distance between the fixed ends of a slender beam, the mechanism can be tuned to transition between monostable and bistable states. This behaves as a sensor and actuator, allowing mechanical signals to pass only when the correct actuation pattern is received. The device is shown to be inherently passive as it returns to a monostable state after actuation. Two different designs have successfully demonstrated this repeatable behaviour. A multi-material PolyJet printed mechanism joining unit cells to a Von Mises Truss, and an SLA printed compliant mechanism coupling unit cells to thin slender beams. A novel approach in performing AND/OR mechanical logic has also been successfully demonstrated by manipulating the mechanical metamaterial when in a bias state. The proposed devices have application in soft robotic systems, the aerospace industry and in the nuclear sector, where there is a need for passive safety systems that are not reliant on electronic systems, and respond to environmental stimuli. The printed mechanisms highlight the potential for mechanical metamaterials to be used as tunable sensors and actuators for future engineering applications.