Wick-free paradigm for high-performance vapor-chamber heat spreaders

In this study, a novel vapor chamber featuring wickless wettability-patterned components is designed, fabricated, and tested. This is the first phase-change heat transfer apparatus comprised entirely of wick-free elements that transport liquid by way of wetting forces generated by precise surface-wettability patterning. Our approach takes advantage of the phase-changing properties of water within a closed loop composed of two opposing, wickless wettability-patterned plates, one acting as an evaporator, and the other designed as a condenser. The plates feature different geometric wettability patterns, each especially designed/engineered to transform a flat rectangular copper plate to a functional component of a low-profile vapor chamber. The wettability pattern of the condenser facilitates spatially controlled dropwise and filmwise condensation and offers an optimal way to move the condensate through specifically built wedge tracks utilizing capillary forces. The wettability pattern laid on the evaporator enables the collection/accumulation and transport of the returning condensate fluid to the heatinput portion where evaporation must be strongest for maximum heat removal. Using this system, we effectively cooled a 0.9 cm2 heated area by spreading the heating power (-200 W) over a 30x larger condenser area. The best performance metrics were thermal resistance 0.18 K/W at 10 W, in-plane thermal conductivity 1.17 kW/ (m.K) at 22 W, and maximum heat flux - 2.2 MW/m2. The present wick-free vapor-chamber heat-spreader apparatus is the first of its type and the simplicity of its design along with its moderate dimensions (making it light and thin) are important advantages that make this system well-suited for a wide range of thermal management applications.