A flexible composite heat sink embedded Ag microchannels for potential flexible electronic applications

A "folding-fan-like" composite heat sink integrating flexible materials and ductile metals is proposed and fabricated. PDMS is served as the flexible "fan surface" for sealing and deformation, and Ag-microchannel is used as the "fan bone" with a fixed end to enhance cooling effect and supporting strength. The polymer-metal-polymer structure combines the advantages of effective heat transfer in metal microchannels with the flexibility of polymer materials. The rigid-flexible composite frame features micro-gaps to enhance heat exchange at the fluid-solid interface, optimize thermal performance and achieve the conformal requirements. Furthermore, a fabrication process is developed for the proposed heat sink involving 0.1 mm micro-gap and Ag pin-fins of 150 µm in width and 300 µm in height. Thermal experiments show that a remarkable 47% increase in thermal power of the embedded Ag microchannel compared to PDMS. Additionally, the implementation of a 0.1mm micro-gap reduces thermal resistance (R) and remarkably increase coefficient of performance (COP) for pump power. Further optimization analysis is conducted on the cover plate, resulting in an increased heat flux of up to 10.3 W/cm
²
. Finally, the bendability and flexibility of the cooling system is initially demonstrated. The proposed concept offers a potential solution for flexible devices or conformal circuits.