Abstract
In this paper we provide evidence that the Cassie-to-Wenzel transition, despite its detrimental effects on the wetting properties of superhydrophobic surfaces, can be exploited as an effective micro-fabrication strategy to obtain highly ordered arrays of biological objects. To this purpose we fabricated a patterned surface wetted in the Cassie state, where we deposited a droplet containing genomic DNA. We observed that, when the droplet wets the surface in the Cassie state, an array of DNA filaments pinned on the top edges between pillars is formed. Conversely, when the Cassie-to-Wenzel transition occurs, DNA can be pinned at different height between pillars. These results open the way to the realization of tridimensional arrays of biological objects.
Highlights
In the last decades a large effort has been devoted to the realization of microstructured superhydrophobic surfaces, exhibiting both high contact angles and low roll-off angles [1,2,3,4]
In this paper we demonstrate the possibility to realize highly ordered arrays of stretched DNA bundles by using superhydrophobic patterned surfaces initially wetted in the Cassie-Baxter state
The pillars were decorated with small features resembling tips. These structures allowed us to obtain a fine control over the DNA bundles position in the plane parallel to the device surface
Summary
In the last decades a large effort has been devoted to the realization of microstructured superhydrophobic surfaces, exhibiting both high contact angles (larger than 140◦-150◦) and low roll-off angles [1,2,3,4] Thanks to their wetting properties, these surfaces are of increasing interest in a variety of fields including self-cleaning and antifouling surfaces, film coating, MEMS/BioMEMS and microfluidics [5,6,7,8]. In the Cassie-Baxter state, the droplet bridges between surface features with trapped air underneath This wetting regime competes with the Wenzel state, where the liquid wets entirely the surface and no air is trapped.
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