Condensation and Wetting Behavior on Hybrid Superhydrophobic and Superhydrophilic Copper Surfaces

Abstract

A novel hybrid superhydrophobic and superhydrophilic copper surface was fabricated using a lift-off process to integrate the benefits of dropwise and filmwise condensation together. The superhydrophilic surface was comprised of microflower like CuO and nanorod Cu(OH)2 with a diameter in the range of 200–600 nm and the superhydrophobic surface was fabricated by chemical modification with Cytop on the hierarchically structured surface of CuO/Cu(OH)2. Wetting condition effect on the hybrid surface was investigated experimentally with a high-speed camera attached to a microscope and an environmental scanning electrical microscope (ESEM). Out-of-plane droplet jumping motion on superhydrophilic region and gravity effect on the droplet motion were examined. Experiment results showed that effective heat transfer coefficients of hybrid superhydrophobic and superhydrophilic surfaces were improved as compared with those of pure superhydrophobic surface. Comparison results between two hybrid surfaces with 2 and 4 mm pattern pitches indicated that the distance reduction between two neighboring superhydrophilic areas can enhance the condensation performance because short distance can promote the microcondensate coalescence and droplets removal.