Microbowl-arrayed surface generated by EBL of negative-tone SU-8 for highly adhesive hydrophobicity

A unique microbowl-arrayed surface demonstrates highly adhesive hydrophobicity similar to a rose-petal. Such a textured surface is generated by electron beam lithography on negative-tone SU-8 resist with X-Y cross-lines scanning. The microbowl array patterned surface possesses an advancing contact angle of 160° and a contact angle hysteresis of 90°, and it is capable of holding a 50 μl aqueous droplet as positioned perpendicularly. The wetting properties of adhesive hydrophobicity can be tuned by varying the exposure dosage in EBL as well as the thickness of the fluorocarbon deposition, both of which can change the curvature of microbowl array with submicron-ridges. Therefore, the contact state on such microbowl-arrayed surfaces can be varied from Cassie-Baxter's to Wenzel's model.