preprints.org > engineering > chemical engineering > doi: 10.20944/preprints202401.1459.v1

Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Version 1 : Received: 18 January 2024 / Approved: 19 January 2024 / Online: 19 January 2024 (06:28:59 CET)

Chemical instability of liquid-repellent surfaces is one of the nontrivial hurdles that hinders their real-world applications. Although much efforts have been made to prepare chemically durable liquid-repellent surfaces, few attentions have been paid to exploit the instability for versatile use. Herein, we propose to create hydrophilic patterns on superhydrophobic surface by taking advantage of its chemical instability induced by acid solution treatment. Superhydrophobic Cu(OH)2 nanoneedles covered Cu plate that shows poor stability towards HCl solution (1.0 M) is taken as an example. Results show that 2.5 min of HCl solution exposure leads to the etching of Cu(OH)2 nanoneedles and partial removal of self-assembled fluoroalkyl silane molecular layer, resulting in the wettability transition from superhydrophobocity to hydrophilicity, and the water contact angle decreases from ~160° to ~30°. Hydrophilic dimples with different diameters are then created on the superhydrophobic surfaces by depositing HCl droplets with different volumes. Afterwards, the hydrophilic dimple patterned superhydrophobic surfaces are used for water droplet manipulations, including controlled transfer, merging and nanoliter droplets deposition. The results thereby verify the feasibility of creating wettability patterns on superhydrophobic surfaces by using their chemical instability towards corrosive solutions, which broadens the fabrication methods and applications of functional liquid-repellent surfaces.

Superhydrophobic surface; chemical instability; wettability pattern; droplet manipulation

Engineering, Chemical Engineering

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