Biomimetic Approach for Preparation of pH Responsive Water Droplet Adhesion on Superhydrophobic Surface. (English)

In nature, many functional superhydrophobic surfaces have been observed, e.g. on lotus leaves, rose petals and morpho butterflies. We focused on the function of rose petals with nano-micro structured surfaces, showing not only strong water repellency but also size-selective adhesion of water microdroplets. Our group has reported that superhydrophobic surfaces composed of polymer pillar arrays are obtained by peeling off the top layer of self-organized honeycomb-patterned porous films. Furthermore, high adhesive superhydrnphobic hydrophilic-dorne and hydrophobic-pillar hybrid structures are obtained by deposition of hydrophilic domains into several pores of the honeycomb film before the peeling process. In this report, we describe the fabrication of a superhydrophobic structured surface showing pH-responsive water microdroplet adhesion prepared from a polystyrene honeycomb film. Adhesion of water microdroplets on the surface is controlled by the pH of the water droplets; pinning is found at low pH and rolling at high pH. This surface is expected to facilitate novel applications in microfluidic devices in order to manipulate water droplets under various environments by facile external stimuli. [ABSTRACT FROM AUTHOR]

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