Integrated Electromagnetic Heating and Fluid Cooling in SMA Actuators via Liquid Metal Circuits

Shape memory alloy-based (SMA) actuators are thermally driven and thus are limited in the frequency of their cyclic actuation responses, especially give the challenges of rapid cooling. In this research effort, liquid metal (LM) has been investigated as an electrically conductive heat transfer fluid for the first in the context of multiphysical SMA-actuators. Gallium-indium-tin eutectic liquid is introduced into complex actuator geometries via internal channels formed in the bulk SMA material. Flow of the liquid metal is effective in rapidly cooling SMA actuators. Thermo-electro-magnetic modeling has also shown that appropriately configured LM channels could be effective as a means to inductively heat the bulk SMA. This research will demonstrate the first inductively heated and fluid-cooled SMA actuator for which LM comprises both the electrical and fluid circuits. To address the critical issue of LM-induced corrosion, focused studies have shown that NiTi is relatively unaffected by this phenomenon at up to 220°C for extended periods of time. To further assesses the viability of integrating LM with SMA-actuators, this research also examines the effects of LM-induced corrosion on the surfaces of SMA bodies undergoing cyclic transformation between martensite and austenite.