EFFECTS OF FEMTOSECOND LASER SURFACE PROCESSING ON HYDRODYNAMIC DRAG OVER A FUNCTIONALIZED SURFACE
Masellas, Dillan A.
Kwon, Young W.
Didoszak, Jarema M.
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Femtosecond laser surface processing (FLSP) is capable of creating several structures on a variety of metallic surfaces that change its hydrodynamic properties. This research focused on the skin friction effects of superhydrophobic and superhydrophilic surface treatments by FLSP. Each type of hydrodynamic surface treatment was studied in the below surface growth (BSG) and the above surface growth (ASG) microstructure form and compared to the performance of a control plate of identical dimensions without a treated surface. The stability of the Cassie state in a fully submerged environment was assessed using an optical microscope. The BSG superhydrophobic surface treatment was submerged in seawater to examine its resistance to biological growth. The BSG superhydrophobic surface treatment’s resistance to biofouling is limited and microstructures appear to provide for adhesion of organisms to the surface. Submerged testing in a rectangular water channel used variable flow rates to achieve Reynolds numbers ranging from 20,000 to 70,000 based on the size of the test sample. Results of these tests showed that the superhydrophilic surface treatments have the same hydrodynamic drag properties as a smooth surface. The superhydrophobic-treated surfaces are ineffective at this range of flow rate due in part to the poor integrity of the trapped Cassie state under static- and flow-induced pressures.
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