A bistable pneumatic actuator based on flexible metamaterials

Abstract:
In this work, we combine the programmable mechanical response of flexible mechanical metamaterials with pneumatic actuation, with the aim of constructing soft machines with mechanically programmed actuation patterns. We design and fabricate flexible metamaterials that undergo snap-through instabilities under tension, enabled by the unit cell comprising double-clamped curved beams. Specifically, we test snapping metamaterials with cylindrical topologies, each composed of a repeating array of four unit cells along the circumferential direction. These metamaterials are fabricated using FDM 3D printing with NinjaFlex filament (TPU 85A), and their nonlinear mechanical response under tension is characterized using a uniaxial testing machine. We design a linear actuator by coupling the flexible metamaterial with a pneumatic single-acting cylinder, thereby placing the nonlinear elasticity of the metamaterial in parallel with the piston. The actuators are characterized in terms of their snapping pressures using a measurement setup comprising a motorized syringe pump for controlled inflation and a pressure sensor.