An inverse opal complex wick for high-performance ultrathin heat pipes

Ultrathin heat pipes (UHPs) have attracted tremendous attention in recent years. However, fabricating UHPs with high heat-transfer efficiency and low thermal expansion remains a challenge. Here, we report a design of an inverse opal complex wick for UHPs. The design enables the wick to have abundant random micropores for the transportation of vapor and ordered nanopores for the return of condensate. With the assistance of a Cu/MoCu/Cu shell, the UHP with a thickness of 0.985 mm can maintain a low coefficient of thermal expansion (7.3E−6 /K) and allow a gallium nitride (GaN) chip to work at a heat flux of 208 W/cm². When the liquid filling ratio reaches 54%, a lower thermal resistance of 0.8 K/W and a higher thermal conductivity of 11,076 W/(m⋅K) are realized. This study demonstrates the successful fabrication of high-performance UHPs, promoting the development of inverse opal wicks from materials to devices.