Bioinspired hairy surfacesPart of:
Nature often uses hairy surfaces to control the interaction of an organism with its environment. Examples are water repellent plant surfaces , the strong adhesion of gecko feet on surfaces  or the insulating properties of animal fur  to name only a few. Many strategies have been reported to generate such surfaces. Among these are conventional methods such as lithography  or microreplication . These techniques, however, are often limited to rather small sample areas and low aspect ratios. We have developed a template assisted method, which addresses these issues. In our process we use porous membranes as templates for microreplication and/or nanodrawing. The aspect ratio of the hairs depends on fabrication parameters such as temperature, time or pore size. In this presentation we will concentrate on conditions needed to accomplish nanodrawing and, hence, long hairs with high aspect ratio. This process requires a balance between the frictional force inside the pore during pull-out and the yield force of the polymer. A theoretical model on these two parameters will be presented and the results of these calculations fit well with our experimental results using HDPE (high density polyethylene) as substrate and a PC (polycarbonate) template (pore diameter 0.6 µm – 10 µm). Furthermore, we will show that the wetting properties of the substrate can be rendered superhydrophobic by this approach.
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