Quick, powerful, and energy-efficient grasping with bio-inspired bistable robotic grippers

Grasping is a fundamental ability in nature, essential for interacting with the environment. From humans to plants, many biological systems have evolved unique ways to grip, hold, and release. Researchers have spent decades developing robotic grippers that can mimic the grasping ability of the human hand. Most robotic gripper designs incorporate soft and flexible materials, such as silicone rubber, origami structures or kirigami patterns. However, these soft robotic grippers have slow response speeds and need continuous energy input to maintain their grasp.

Introducing bistable structures into robot grippers has emerged as a viable solution to this problem. Bistable structures have two stable mechanical states: open and closed. Once a bistable gripper switches states, it can hold that state without continuous energy or force input.  Transitions between these states occur in a rapid snap-through action that can occur in the blink of an eye. A key limitation, however, of such structures is their fixed energy barrier. The energy barrier is the amount of energy or force required to trigger the switch between the open and closed states. In contrast, natural organisms can dynamically modulate their energy barriers. This rigidity restricts the adaptability and performance of bistable robotic grippers after the initial setup, making them unsuitable for many real-world tasks.

In a groundbreaking study published in the journal Research on June 19, 2025, researchers developed an innovative bio-inspired bistable robotic gripper, with a tunable energy barrier. “Seed pods belonging to the genus Impatiens exhibit a remarkable energy barrier modulation mechanism. During growth, the pods maintain a high energy barrier to prevent premature seed dispersal. Upon maturation, the energy barrier is reduced considerably, making them highly sensitive to external stimuli. Consequently, even a raindrop can trigger the mature pods to explode, facilitating efficient seed dispersal. Inspired by this dynamic energy barrier modulation, our bistable robotic gripper achieves energy-efficient and sensitive manipulation,” explains Dr. Peng from Dalian University of Technology, China.  

The robotic gripper features a bistable elastic beam, mounted at the bottom of finger like grippers on each end through clamps. The clamps are connected to rotating shafts, controlled by a motor, allowing dynamic energy barrier modulation. Initially, the beam remains in a monostable flat configuration. To activate the mechanism, the motor actuates the rotating shaft, bending the beam slightly upwards and transitioning it into a bistable structure.

In this open state, the beam has a low energy-barrier, making it highly sensitive. When an object presses against the beam, it bends inwards, snapping to the closed state while maintaining the low energy barrier. To improve grasping power further, the motor can further bend the beam, significantly increasing its energy barrier and consequently, its strength and stability. This process is fully repeatable, allowing the gripper to adapt to different tasks and environments.

The tunable energy barrier enables the gripper to achieve rapid, compliant, and powerful, grasping behavior. In its low energy barrier state, the gripper required a mere 0.66 newtons of triggering force to initiate grasping. In the high energy barrier closed state, it can withstand 12.08 newtons of force before releasing, demonstrating an exceptional failure-to-triggering ratio.

To demonstrate its practical applications, the researchers integrated the robotic gripper into an unmanned aerial vehicle (UAV). This helped the UAV interact with tree branches and perch like a bird with minimal energy consumption. In the high energy barrier state, the UAV remained firmly fixed to a branch, resisting even strong wind gusts without needing continuous energy input. To disengage, the robotic gripper could be easily controlled via Bluetooth. Beyond perching, this integration significantly broadens the functionality of the UAV, enabling it to deploy onboard sensors for environmental monitoring or anchor on to various surfaces and objects.

“With its quick response, programmable interaction forces, and simple yet efficient design, our robotic gripper opens new avenues for next-generation robotic systems. This unique mechanism can significantly expand the functionality of robots for diverse applications,” remarks Dr. Wu.

This breakthrough design marks a significant step forward for robotic grippers, paving the way for more advanced robotic systems.

About the journal

Launched in 2018, Research is the first journal in the Science Partner Journal (SPJ) program. Research is published by the American Association for the Advancement of Science (AAAS) in association with Science and Technology Review Publishing House. Research publishes fundamental research in the life and physical sciences as well as important findings or issues in engineering and applied science. The journal publishes original research articles, reviews, perspectives, and editorials. Impact factor = 10.7, Citescore = 13.3.

Sources: https://doi.org/10.34133/research.0737