Fast Capillary Wicking on Hierarchical Copper Nanowired Surfaces with Interconnected V-Grooves: Implications for Thermal Management

Evaporation and boiling heat transfer on micro/nanostructured surfaces with superior wicking capability is an efficient cooling approach for high heat flux removal. The enhancement of the wicking capability has been identified as a key mechanism to enhance heat transfer efficiency and prevent thermal crisis. However, the capillary wicking capability is limited by the trade-off between the capillary pressure and the viscous resistance on the length scale of the structure feature. Here, we report a rapid capillary wicking capability on hierarchical nanowired surfaces with interconnected V-grooves, whose wicking coefficient reaches 6.54 mm/s0.5. This is attributed to the highly uniform copper nanowires which provide prominent capillary pressure while the interconnected V-grooves provide liquid film transport channels to reduce the viscous resistance. We experimentally investigated the effect of nanowire spacing, V-groove fraction, and V-groove depth on the wicking coefficient for various liquids with surface tension to viscosity ratios from 6 to 81. Larger fractions and depths of such V-grooves lead to higher wicking coefficients. Moreover, the wicking coefficient is increased as the surface tension to viscosity ratio of the liquid increases. This work offers guidelines for designing and optimizing hierarchical structures to enable ultrafast liquid film wicking, thus highlighting the thermal management potential.