Thermomechanics of Picoliter Liquids Encapsulated in Metal Microarchitectures

Probing the mechanical behavior of liquids at the nanoscale-especially under hydrostatic stress with various strain rates and extreme temperature conditions-holds significant potential for advancing microfluidic, biomedical, and energy systems. However, it remains experimentally challenging due to the inherent difficulties in encapsulation of liquid at micro/nanoscale and in accurately applying and measuring stress within confined microscale environments. In this work, we present a novel single-step method for liquid encapsulation at the microscale and subsequent in situ micromechanical testing at extreme dynamic thermomechanical conditions. Localized electrodeposition in the liquid process enables the direct formation of hollow copper microarchitectures containing picoliters of liquid. The presence of the encapsulated liquid was verified via structural analysis at cryogenic and elevated temperatures. We investigated the mechanical role of the confined liquid through compressive tests, demonstrating its incompressibility at room temperature and its enhanced load-bearing capacity in the ice phase at -160°C. These results reveal enhanced energy dissipation due to the size-dependent strength of ice. Additionally, we evaluated the tensile response of copper-ice composites at -160°C using microfabricated push-to-pull structures. Our findings outline a new pathway for encapsulation of liquids in metal microarchitectures that could aid and impact fields of microelectronics, pharmaceuticals, and energy storage.