Deformable High Loading Liquid Metal Nanoparticles Composites for Thermal Energy Management

The emergence of soft electronics has led to the need for thermal management with deformable material. Recent efforts have focused on incorporating EGaIn microparticles (≈10¹ µm) into elastomer forming a thermal conductive composites. However, the shape deformation and coalescence of EGaIn particles under mechanical stress often lead to parasitic electrical conduction, imposing limitations on its utilization in thermal management. Increasing the loading of EGaIn nanoparticles (>20 vol%) often leads to brittleness of the composite. Herein, a strategy to obtain thermally conductive and soft elastomers with a high-volume ratio of EGaIn nanoparticles (44 vol%) is introduced. Surface modification of EGaIn nanoparticles with carboxylic acid terminated polydimethylsiloxane (COOH-PDMS-COOH) coupled with the in situ formation of a PDMS matrix by crosslinking with the surface-modified EGaIn nanoparticles leads to dense EGaIn nanoparticles in a PDMS matrix with effective thermal transport. Notably, despite the high-volume ratio of EGaIn nanoparticles in the elastomer, the composite maintains a low elastic modulus (6.91 kPa) and remains electrically insulating even under mechanical stress. In addition, a distinctive anisotropic thermal conductivity of the elastomer is established upon stretching. This elastomer can be utilized as a thermal interface layer for thermoelectric devices. The resulting thermoelectric performance has promise in applications such as wearable thermo-haptic or thermo-sensing devices.