Abstract
In this article, we report a simple approach to generate micropillars (whose top portions are covered by sub-micron wrinkles) on the inner surfaces of polystyrene (PS) microchannels, as well as on the top surface of the PS substrate, based on strain-recovery deformations of the PS and oxygen reactive ion etch (ORIE). Using this approach, two types of micropillar-covered microchannels are fabricated. Their widths range from 118 μm to 132 μm, depths vary from 40 μm to 44 μm, and the inclined angles of their sidewalls are from 53° to 64°. The micropillars enable these microchannels to have super-hydrophobic properties. The contact angles observed on the channel-structured surfaces are above 162°, and the tilt angles to make water drops roll off from these channel-structured substrates can be as small as 1°.
Highlights
It is observed that the leaf surfaces of some lotuses have dual-size roughnesses, i.e., micropillars are covered by sub-micron pillars [1,2]
Part of the PS located underneath the hollow channel was partially etched by the oxygen reactive ion etch (ORIE) using the stencil as a mask
In the third step (Figure 1c), using Ag microdots as masking patterns, micropillars were generated on the PS block using oxygen reactive ion etch (RIE)
Summary
It is observed that the leaf surfaces of some lotuses have dual-size roughnesses, i.e., micropillars are covered by sub-micron pillars [1,2]. Their focus is on the generation of dual-size roughnesses on flat surfaces, while little work has been done to create such structures on the non-flat inner surfaces of microchannels Existing photolithographic approaches, such as ultra-violet (UV), electron-beam, X-ray, and ion-beam, employ vertical light exposure to transfer patterns. Ag dots and lines are thin (their thicknesses are less than 1 μm), water is easy to have contact with the bottoms of the grooves located between these patterns, making the micropatterns losing their function of reducing f SA To avoid this contact problem for further decreasing f SA , in this work, we modify the fabrication approach of our previous work [24], and make it suited at generating micropillars on the inner surfaces of a microchannel.
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