A Novel Evaporator Integrated with Wettability Pattern for Improving Thermal Performance of an Ultrathin Vapor Chamber

Abstract

We investigated the thermal performance of a novel multiscale evaporator of a 0.23 mm thickness ultrathin vapor chamber which combines a microstructured wettability patterned surface with a nanostructured woven mesh wick. The microstructured wettability patterned surface underneath the nanostructured woven mesh wick can pin the three-phase contact lines on the hydrophilic/hydrophobic boundaries, enlarging the area of thin-film evaporation. Besides, the nanostructured mesh not just provides a large amount of backflow water for maintaining the evaporation on the three-phase contact lines, but also gives more thin-film evaporation area owing to its needlelike nanostructure. Microstructured wettability pattern is fabricated on the inner surface of the evaporator and the wick is pressed onto the wettability patterned surface by a micropillar array to make them close contact with each other. The micropillar array fabricated by electroplating on the inner surface of the condenser is also used to support a vapor core as a vapor flow path. The horizontal and vertical thermal resistances are measured to evaluate the thermal performance of the ultrathin vapor chamber for different charge amounts of water when the input heat flux ranges from 8.59 W/cm2 to 23.91 W/cm2 and the heat sink is 22 ℃ forced air cooling with 6.875 cfm flow rate. The measurement results show that the novel evaporator not just greatly reduce the horizontal thermal resistance, but also lower the vertical thermal resistance compared with the evaporator without wettability pattern. The highest in-plane effectivity of the ultrathin vapor chamber with the novel evaporator can reach 11499.5 W/(m•K) at 23.91 W/cm2, giving a 212.7% improvement compared with the ultrathin vapor chamber without wettability pattern on its evaporator.