Mechanically Rupturing Liquid Metal Oxide Induces Electrochemical Energy

Liquid metals, such as Gallium‐based alloys, have unique mechanical and electrical properties because they behave like liquid at room temperature. These properties make liquid metals favorable for soft electronics and stretchable conductors. In addition, these metals spontaneously form a thin oxide layer on their surface. Applications made possible by this delicate oxide skin include shape reconfigurable electronics, 3D‐printed structures, and unconventional actuators. This paper introduces a new approach where liquid metal oxide serves as an electrochemical energy source. By mechanically rupturing their surface oxide, liquid metals form a galvanic cell and convert their chemical energy to electrical energy. When dispersing liquid metals into an ionically‐conductive liquid to form emulsions, this composite material can provide ∼500 mV of open‐circuit voltage and up to ∼4 μW of power. Protected by the naturally occurring oxide skin, the passivating oxide layer of the liquid metal shields it from self‐discharge over time. The device is also stable in harsh environments, such as high temperature or aquatic conditions. Future applications of this device are demonstrated by designing a strain‐activated stretchable battery and a pressure‐sensitive self‐powered keypad. These findings may unlock new pathways to design stretchable batteries and harness their inherent energy for self‐powered robust devices. Liquid metals spontaneously form protective oxide skins on their surfaces when exposed to oxygen. While the oxide layer is generally considered a nuisance, this article reports a mechanism that harnesses the electrochemical energy of the spontaneous re‐growth of liquid metal oxide after being damaged by mechanical disturbances. This discovery enables the design of strain‐activated stretchable batteries and self‐powered soft devices.