Spatial Control of Heterogeneous Nucleation on the Superhydrophobic Nanowire Array

Abstract

Condensation is a common phenomenon and is widely exploited in power generation and refrigeration devices. Although drop‐wise condensation offers high heat and mass transfer rates, it is extremely difficult to maintain and control. In this study, the ability to spatially control heterogeneous nucleation on a superhydrophobic surface by manipulating the free energy barrier to nucleation through parameterizing regional roughness scale on the Si nanowire array‐coated surface is reported. Water vapor preferentially condenses on the designed microgrooves on the Si nanowire surface and continuous shedding of the drop‐wise condensate is observed on the surface. The nucleation site density can also be manipulated by tailoring the density of the microgroove on the surface. Moreover, the cycle time on the Si nanowire array with microgrooves is approximately ten times smaller than that on a plain Si surface. This suggests that potentially high heat and mass transfer rates can be achieved on the surface. The insight from this study has implications in enhancing energy efficiency in a wide range of thermal energy conversion systems.

Heterogeneous nucleation capability of conical microstructures for water droplets

“…9,10 Subsequently, the CNT model has been modied to obtain more accurate results, [11][12][13][14] and the effect of a planar substrate and the heterogeneous nucleation model were considered. 25 On the other hand, the relationship between the substrate structure and the nucleation process, [26][27][28][29][30][31][32][33] and the effect of micro particles on the nucleation rate, were also widely investigated. 25 On the other hand, the relationship between the substrate structure and the nucleation process, [26][27][28][29][30][31][32][33] and the effect of micro particles on the nucleation rate, were also widely investigated.…”

Resistant energy analysis of self-pulling process during dropwise condensation on superhydrophobic surfaces

“…The formation of nucleation embryos in nanostructure cavities and in the rst tier pillar cavities is ubiquitous since the critical nucleation radius of water is around tens of nm. The free energy barrier to condensate formation in the roughness cavity, i.e., the change in the free energy associated with embryo formation, could be calculated as: 17,18 DG ¼…”

Synthesis of superhydrophobic fluorinated polystyrene microspheres via distillation precipitation polymerization

“…There have been two ways for the preparation of superhydrophobic surface: (i) control of the topography of the hydrophobic surface to increase the surface roughness via Blotus^effect and (ii) chemical modification to lower the surface energy. The surface roughness can be increased via fabrication of hierarchical structures using different approaches, such as electrodeposition [5], electrospinnning [6], nanowire arrays [7], and hetero-coagulated self-assemble of colloidal systems [8]. It is necessary to design and synthesize prepolymer with unique structure and morphology with the subsequent techniques for the formation of rough surface.…”