Bulk Electrochemical Actuators for Microscopic Robots and Microscale Medical Tools*

Actuator energy density defines their applications: a strong microscale actuator can drive microscopic robots with heavy, complex circuitry and would allow for microsurgical tools with an ability to cut through stiff human tissue. We demonstrate microscopic electrically controllable actuators fabricated using CMOS compatible methods exhibiting a larger work density than any offered actuator technology. The devices consist of a bimorph: an expanding Pd layer and passive Ti layer that resists the Pd expansion, generating a moment that results in bending. In an aqueous electrolyte, Pd expands by 3.1% via application of a voltage (~ -1V), catalyzing generation of H that diffuses into the bulk Pd and contracts at ~ 1V, driving out absorbed hydrogen. This work expands on prior actuators utilizing a surface stress, which had limited output energy. The bulk actuators achieve a very small bending radius of 3.8 um when 230 nm thick. Results relating to the measured output force and movement through a gel exhibiting electrochemical and mechanical human tissue properties will be presented.