Material-Form-Scale Effects of Shape Memory Alloy (SMA) Actuators

Smart materials are widely used in sensors, actuators and robotics, and their multi-functional capabilities enrich engineering applications. In this presentation, material designs, form factors and scale effects of Ni-Ti SMA are discussed. As an example of material designs, soft smart composite (SSC) based on SMA and anisotropic polymer fibers embedded in soft elastomer matrix is introduced. Actuation characteristics of the SSC and its applications to various mechanical systems are presented. To extend conventional form factors, shape-memory knit actuators are developed in order to produce high actuation force and stretchable features. Scaling down to meso/micro level, 25~40 micrometer thick SMA wires in SSC show 35 Hz, and light-driven actuation of 500 nm-thin SMA frames enhance the actuation frequency up to 1,600 Hz. The actuator is applied to make a standalone microrobot actuated by remote laser beam, and several micro robots are controlled individually to form a swam activity as a group. Extending nano fabrication to SMA, meta surfaces are introduced to the micro actuator by focused ion beam to show wavelength selectivity of the SMA actuators.