Creating micro-scale surface topology to achieve anisotropic wettability on an aluminum surface

Abstract

A technique for fabricating micropatterned aluminum surfaces with parallel grooves 30 µm wide and tens of microns in depth is described. Standard photolithographic techniques are used to obtain this precise surface-feature patterning. Positive photoresists, S1813 and AZ4620, are selected to mask the surface, and a mixture of BCl 3 and Cl 2 gases is used to perform the etching. Experimental data show that a droplet placed on the micro-grooved aluminum surface using a micro-syringe exhibits an increased apparent contact angle, and for droplets condensed on these etched surfaces, more than a 50% reduction in the volume needed for the onset of droplet sliding is manifest. No chemical surface treatment is necessary to achieve this water repellency; it is accomplished solely by an anisotropic surface morphology that manipulates droplet geometry and creates and exploits discontinuities in the three-phase contact line. These micro-structured surfaces are proposed for use in a broad range of air-cooling applications, where the management of condensate and defrost liquid on the heat transfer surface is essential to the energy-efficient operation of the machine.(Some figures in this article are in colour only in the electronic version)

Droplet motion on inclined heterogeneous substrates

“…They also deduced an equation for the critical inclination angle based on energy considerations to explain qualitatively their observations, whose validity was later questioned by Roura & Fort (2002). Sommers & Jacobi (2006 performed a series of experiments with microgrooved substrates, where they observed that the motion was greatly influenced by the characteristics of the heterogeneities and their orientation relative to gravity. More specifically, they observed reduced critical angles when the groove-spacing is sufficiently small.…”

Fabrication of Bioinspired Actuated Nanostructures with Arbitrary Geometry and Stiffness

“…For example, it can lead to anisotropy in the adhesive properties [24] of gecko feet on surfaces or to anisotropy in wettability in some man-made nanostructured surfaces. [25] The elliptical cross-section of superficial neuromastsstructures that detect water flow on the body surface of fish and amphibians-provides the ability to map the direction of water flow. [13] Motivated by these considerations we have developed a technique, by which we can easily control the geometry of the nanostructures to form both tilted and twisted posts, as well as different 2D symmetries and cross-sectional shapes, using the same original master.…”

Switch isotropic/anisotropic wettability via dual-scale rods

“…Anisotropic wettability has attracted more attentions of the research community. [1][2][3][4][5][6][7][8][9][10][11][12][13] Inspired by the natural microstructure like rice leaf, artificial anisotropic wetting surfaces have been studied recently. Dual-scale micro-nano structures have been prepared by different techniques and their wettability have been studied.…”