Liquid metal-based flexible heat sink for adaptive thermal management

The deformable heat sinks are critical for flexible electronics, wearable personal thermoregulation and energy management. However, the available soft polymer materials with poor thermal characteristics face challenges in achieving efficient heat transfer. Herein, we report an excellent flexible heat sink enabled by a gallium-based liquid metal (LM) for adaptive thermal management. The flexible heat sink is prepared by embedding LM droplets and copper particles into the elastic matrix forming solid-liquid multiphase composites, achieving a considerable thermal conductivity (3.5 W/mK@300 % stretching deformation), outstanding high-temperature resistance, and excellent conformity. The cooling and hydrodynamic characteristics of the flexible heat sink with different structures, including parallel (plane), S-type (plane), and annular (three-dimensional) channels, are investigated and optimized by the thermal experiment and developing the fluid-structure coupling numerical simulation. The results show that the maximum temperature and heat flux achieved by the S-type heat sink are 36.7 degrees C and 0.68 W/cm2 respectively, due to the secondary flow enhancing convection thermal transfer intensity. The annular heat sink has outstanding advantages in suppressing temperature and improving uniformity because the thermal transfer path is optimized by stretching, especially for larger deformation. Furthermore, the annular heat sink has been proven feasible for lithium battery cooling and pre-insulation.