Active morphing robot inspired by the pre-strained fiber structure of the Venus flytrap

In this study, we present a novel design of an active morphing robot inspired by Venus flytrap [12-15]. The Venus flytrap has a pre-strained fiber structure which induces the bistability of the leaf that enables fast trapping motion via snap through. This fast shape changing motion can also be induced in a fiber based laminated composite products. Most composite products, i.e., tails of a helicopter, badminton racquets, are manufactured symmetrically and do not possess this kind of property. However, unsymmetrically laminated composite structures pre-strained by residual thermal stresses induced by thermo-mechanical expansion during the curing process [1-6] possess bi-stability. The bi-stable laminate has out-of-plane deformation which induces two cylindrical stable shapes. These shapes are changeable via snap-through action by applying bending moment at the edge of the laminate. The advantage of the bistable structure is that it requires input energy only when it changes its shape from one stable shape to the other. Several studies in morphing structures using this bistable structure have been investigated recently [7-10]. To develop an active morphing structure using snap-through of the bistable laminate, the shape memory alloy (SMA) spring actuator has been employed to generate the bending moment [11]. By embedding SMA spring actuator to the bistable laminate, the structure is actively deformable. We call this structure BIMAC: Bistable Intelligent Morphing Active Composite plate. For the application of BIMAC, we try to mimic the function of the Venus flytrap (Dionaea muscipula), which is gripping within 100 ms after triggering. The robot can close and open its bistable laminate leaves repeatedly with a closure time of approximately 100 ms, which is similar to the Venus flytrap. Future work will examine several issues for enabling stable and robust gripping.