The Venus flytrap uses bistability, the structural characteristic of its leaf, to actuate the leaf's rapid closing motion for catching its prey. This paper presents a flytrap-inspired robot and novel actuation mechanism that exploits the structural characteristics of this structure and a developable surface. We focus on the concept of exploiting structural characteristics for actuation. Using shape memory alloy (SMA), the robot actuates artificial leaves made from asymmetrically laminated carbon fiber reinforced prepregs. We exploit two distinct structural characteristics of the leaves. First, the bistability acts as an implicit actuator enabling rapid morphing motion. Second, the developable surface has a kinematic constraint that constrains the curvature of the artificial leaf. Due to this constraint, the curved artificial leaf can be unbent by bending the straight edge orthogonal to the curve. The bending propagates from one edge to the entire surface and eventually generates an overall shape change. The curvature change of the artificial leaf is 18 m(-1) within 100 ms when closing. Experiments show that these actuation mechanisms facilitate the generation of a rapid and large morphing motion of the flytrap robot by one-way actuation of the SMA actuators at a local position.

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This paper presents a bio-mimetic flytrap robot based on the Venus flytrap, which has rapid snap-through motion. The robot employs a bi-stable unsymmetrically laminated carbon fiber reinforced prepreg (CFRP) structure, which has a bi-stable mechanism that is similar to the Venus flytrap's passive elastic mechanism. By embedding shape memory alloy springs, large deformation is induced and bi-stable structure can be triggered to snap through. The robot's working performance shows that the leaves close in about 100ms, and this time for closure is almost the same as that of the Venus flytrap. This concept of the flytrap robot can be applied to rapid grippers of various sizes.

Fleas have a unique catapult mechanism with a special muscle configuration. Energy is stored in an elastic material, resilin, and the extensor muscle. Force is applied by the extensor muscle to generate a torque. Energy is released as a small triggering muscle reverses the direction of the aforementioned torque. A flea can jump 150 times its body length using this elastic catapult mechanism. In this paper, a flea-inspired catapult mechanism is presented. This mechanism can be categorized as an active storage and active release elastic catapult. Owing to its unique stiffness change characteristic, a shape-memory-alloy coil spring actuator enables the mimicking of the flea's catapult mechanism. Two types of flea-inspired jumping mechanisms were developed for verifying the feasibility of applying the concept to an efficient jumping robot. The first prototype has a flea-like appearance and the second is simplified to contain just the essential components of the flea-inspired catapult mechanism. The two prototypes are 20-mm-and 30-mm-long and can jump 64 cm and 120 cm, respectively. This unique catapult mechanism can be used not only for jumping robots but also for other small-sized robots to generate fast-releasing motion.

This paper presents a second prototype of the flytrap robot which mimics the fast snap-through motion of the Venus flytrap, the previous version of the robot. This second prototype employs a new type of unsymmetrically laminated carbon fiber reinforced prepreg (CFRP) structure which has two different curvatures, and an SMA spring actuator. To estimate the force of snap-through the structure, a linear beam bending model is introduced and a force-displacement experiment is demonstrated. Based on the numerical and experimental results, the flytrap robot can be closed rapidly and opened for re-load. The closure time is about 100ms.