Nanofluids Evaporation Kinetics on Microstructured Superhydrophobic Surfaces

In this paper, we experimentally studied the evaporation kinetics of sessile droplets of nanofluids with systematically varying particle sizes on superhydrophobic surfaces of well-defined micro-post structures. The superhydrophobic surface patterns were fabricated on a silicon wafer by photolithography and deep reactive ion etching (DRIE) at cryogenic temperature followed by Teflon coating. The 0.01 wt% suspensions of gold (Au) nanoparticles with varying sizes (5, 50, and 250 nm in diameter) were tested as nanofluids for the evaporation kinetics including the contact angle, base diameter, height, volume and evaporation rate by using a goniometer. The dryout patterns were investigated by using scanning electron microscopy (SEM). The results show that the surface topography and nanoparticle sizes have significant effects on the initial contact angle, profile evolution, wetting transition, evaporation rate, and dryout deposition pattern of the nanofluid droplets.