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In this paper, we present superhydrophobic micro/nano dual structures (MNDS). By KOH-etching of silicon, well-designed microstructures, including inverted pyramids and V-shape grooves, are first fabricated with certain geometry sizes. Nanostructures made of high-compact high-aspect-ratio nanopillars are then formed atop microstructures by an improved controllable deep reactive ion etching (DRIE) process without masks, thus forming MNDS. Resulting from both the minimized liquid-solid contact area and the fluorocarbon layer atop deposited during the DRIE process, the MNDS show a reliable superhydrophobicity. The contact angle and contact angle hysteresis are -165 degrees and less than 1 degrees, respectively. This superhydrophobicity of MNDS is very stable according to squeezing and dropping test, even in high voltage conditions with the electrowetting threshold voltage of -300 V. Therefore, this micro/nano dual-scale structure has strong potential applications to the self-cleaning surface and superhydrophobic micro/nano fluidics.

Abstract. Electrowetting displays (EWD) is a novel technology, based on the variation in coverage of a colored oil film in pixels via application of an electrostatic force. These pixels are usually fabricated by photolithography, which seriously limits materials selection and large area fabrication. In this paper, we demonstrate the feasibility of a novel method, nanoimprint lithography (NIL), to fabricate EWD pixels. Controllable contraction and recovery of oil film in single EWD pixels was realized. Compared with conventional lithography, NIL provides a cost-and time-saving technique that generates comparable display properties and is able to be easily extended to the mass production.

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