Wirelessly Powered Micro Soft Bellows Actuator with 3D Helix Coils

Micro inductors for wireless power transfer, which had only been built in 2D spiral structures, are realized in 3D helix structures to receive more power, and applied to a thermopneumatic soft micro bellows actuator to demonstrate untethered actuation. Although the 3D helix inductor can acquire more magnetic flux linkage than the 2D spiral inductor, the conventional microfabrication technique inherently produces elements on 2D planes, thus limiting the achievement of complete 3D structures. In this study, the 3D micro helix coils are fabricated using the 3D-printed soluble mold technique to produce the 3D Joule heaters with a larger heating area than the 2D heaters as well as the 3D receiving inductors for improved wireless power transfer. The 3D helix inductor receives more power than the 2D spiral inductor, heating the Joule heater up to 176.1% higher temperature. Eventually, the wireless actuator with the 3D helix coils operates repeatedly up to a stroke of 484 µm. Therefore, the 3D micro inductors can provide an excellent approach to the untethered soft micro robots without heavy payloads such as batteries.