A research team led by Professor Il-Kwon Oh (Korea Advanced Institute of Science and Technology) announced that they have developed a wearable prosthetic hand that can perform various tasks and a biomimetic robotic inspired by the unique structure of a cat's claws, using artificial muscles.

The artificial muscle that the research team developed is a shape memory alloy (SMA) spring which contracts to its memorized shape upon heating it. Similar to the skeletal muscle of our body, the artificial muscle contracts when electrical signal for Joule heating is applied and relaxes during cooling. However, due to sluggish cooling of the SMA, its actuation speed was severly limited by its cooling speed.

To accelerate the actuation speed of SMA artificial muscle, the research team grew a copper (Cu) nanowire forest on the surfaces of SMA spring to increase the surface area by 15 times and boost thermal convection. As a result, the Cu nanowire grown SMA spring showed 2 times faster actuation speed compared to a bare SMA spring. With such faster actuation speed, the Cu nanowire grown SMA artificial muscles were employed in a versatile prosthetic hand to bend and flex fingers. Moreover, the cat’s unique retractable claws were mimicked by accelerated SMA artificial muscle to demonstrate a fully tunable frictional force just like how cats do.

Prof. Oh said that “Our approach to accelerating the actuation speed of SMA artificial muscle will open up more possibilities for applications of SMA artificial muscle in various engineering applications such as soft robotics, assistive robotics, biomimetics, and wearable power suit, in near future”.

[Reference] Oh et al. (2022) “Cooling-Accelerated Nanowire-Nitinol Hybrid Muscle for Versatile Prosthetic Hand and Biomimetic Retractable Claw” Adv. Funct. Mater.

[Main Author] Saewoong Oh (Korea Advanced Institute of Science and Technology), Il-Kwon Oh (Korea Advanced Institute of Science and Technology)* Contact : Professor Il-Kwon Oh, ikoh@kaist.ac.kr