Reprogrammable bistable structure makes soft grippers faster

(Nanowerk News) Soft grippers have the advantages in human-machine interactions while most of them suffer from low response time. Bistable structures could improve this characteristic, but current bistable grippers are limited by the designed structural parameters and the grasping modes.
Recently, a research team led by Dr. LI Yingtian from the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences (CAS), has proposed a novel type of soft gripper based on reprogrammable bistable actuator. Compared with existing bistable actuators, the proposed actuators could be controlled to perform diverse sensitivities and therefore exhibit multiple gripping modes and various response speeds by simply reprogramming this structure.
The study was published in IEEE/ASME Transactions on Mechatronics ("Reprogrammable Bistable Actuators for Multimodal, Fast, and Ultrasensitive Grasping").
The reported soft gripper consisted of a bistable frame and soft pneumatic bi-directional actuator, linked by an un-stretchable cable. In the programming process, the pneumatic actuator shortened its longitudinal length to pull the frame through the cable, resulting to gradually accumulation of the strain energies of the lateral plates. Therefore, the energy barrier required to be broken to trigger the fast snap-through of the structure decreased. In this way, the structure exhibits its reprogrammable characteristic by controlling the structure to various intermedium states with different sensitivity.
In this work, the researchers analyzed the force-displacement relationship of the frame and the predicted trigger forces. The results showed that the force required to trigger the fast snap-through could be less than 0.005 times of its maximum value, simply by reprogramming the structure’s sensitivity.
To intuitively demonstrate the uniqueness of the proposed actuator, the researchers prototyped multiple grippers to conduct multimodal, fast, and ultrasensitive grasping tests. The gripper could even be able to respond to the contact of the swimming fish and capture it within 0.18 s.
"Our research team has been investigating the ultra-tunable bitable structure for a few years and published and submitted a series of research papers in this area, including the Cell sister Cell Reports Physical Science," said Dr. LI. "Other works utilizing these structures are being studied to prove their practicability and broaden the applications in the fields of robotics, bioengineering, etc."
Source: Shenzhen Institute of Advanced Technology (Note: Content may be edited for style and length)
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