Researchers from University of Michigan designed a modular material capable of adopting several force-generating and energy-storing postures
Skeletal muscle is a muscle tissue that is actively controlled by vertebrates. It has a unique microscopic structure that enables it to generate force and regain lost tension. Replication of these characteristics of muscles can facilitate development of robust and adaptable components for robots. Now, a team of researchers led by Narayanan Kidambi of the University of Michigan, Ann Arbor, created a modular material capable of adopting multiple geometric arrangements. The material can switch between arrangements to generate force and store mechanical energy.
Muscle fibers comprise parallel filaments of proteins, which are linked by cross bridges. These cross bridges change their shape and orientation to force the filaments to slide relative to each other. This results in muscle contraction. The cross-bridge structure inspired the team to design a square of silicone rubber, which is 15 mm on a side, and is embedded with four holes. The circular holes deform when this module is compressed and adopts one of several stable configurations. For instance, the scrunched holes might show inclination toward one side. Moreover, some scrunched holes might experience flat horizontal projection while adjacent holes flatten vertically. Each configuration is capable of storing a different quantity of elastic energy. A switch between two configurations produces a shear force perpendicular to the compression direction.
The material is most efficient when multiple modules are lined up. The ensemble can cycle through the different configurations for each module to deliver a shear force with a range of magnitudes and directions. However, the team is currently depend on manually nudging the compressed material into specific configurations with a pair of tweezers. The team is focused on replacing the tweezers with actuators as such development can allow the shapes to be controlled remotely. The researchers expect that such a modular system could be a novel building block for soft robotics designs. The research was published in Physical Review E on October 09, 2018.