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.