Researchers at the Chinese Academy of Sciences have developed an ultra-tunable bistable customizable for different robotic applications.
Natural bistable structures amplify force and respond swiftly to small inputs. Exploiting their inherent bistability and instability can improve robot performance. However, studies on bistable structures mainly consider stable states, neglecting intermediate states with tunable energy barriers.
A research team led by Dr. LI Yingtian from the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences have developed an ultra-tunable bistable structure that features programmable energy barriers and trigger forces with differences of several orders of magnitude. The structures are customizable for different robotic applications with varied configurations, materials, and actuation methods.
The bistable structure has developed by folding a sheet material with a specific crease pattern. It has stable, metastable, and many intermediate states. During the transition from metastable to a stable state, a critical point has been reached where stored strain energy is at its highest, causing a fast snap-through. The work reported programmable energy barriers for many intermediate states before the bistable structure reaches its critical point. Reshaping from metastable to intermediate states lowers the energy barrier, requiring smaller external stimulations to trigger snap-through. Energy barrier decrease leads to more delicate stimulation, resulting in a wide range of adjustable trigger forces for the controllable bistable structure.
The researchers showed tunability by conducting experiments that tuned trigger force to 0.1% of maximum value and achieved a 107-fold increase in lifted weight with grippers made from proposed structures with different parameters. The structure can be tuned to an ultra-sensitive state that responds to gentle or insensitive stimulation where a 110g steel ball cannot break its energy barrier. Various prototypes have been developed to showcase the structure’s potential in different applications, such as a robotic flytrap, grippers, jumper, swimmer, thermal switch, and sorting system. The prototypes demonstrate the flytrap’s sensitivity, the catcher’s high-speed capability, and the jumper’s impressive height.
The wide range of applications for the proposed structure showcases its superior performance. The researchers believe this work could expand the boundaries of bistable structure design and inspire future designs in fields such as robotics, biomedical engineering, architecture, and kinetic art.
Reference: “Ultra-tunable bistable structures for universal robotic applications” by Yongkang Jiang, Yingtian Li, Ke Liu, Hongying Zhang, Xin Tong, Diansheng Chen, Lei Wang and Jamie Paik, 18 April 2023, Cell Reports Physical Science. DOI: 10.1016/j.xcrp.2023.101365