Study of model superoleophobic surfaces fabricated with a modified Bosch etch method.

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Superoleophobic surfaces repel oils and other low-surface-tension liquids.
• Controlling surface topography is key to achieving stable superoleophobicity.
• Previous methods often linked geometric parameters, limiting design flexibility.

Purpose of the Study:

• To develop a novel fabrication method for superoleophobic surfaces.
• To investigate the role of overhanging cap structures on surface properties.
• To decouple geometric parameters for independent control.

Main Methods:

• Fabrication of pillar surfaces with overhanging caps using a new technique.
• Contact angle measurements using water, ethylene glycol, and hexadecane.
• Analysis of liquid behavior in relation to surface structure and Cassie fraction.

Main Results:

• The new method allows independent control over pillar diameter, separation, and Cassie fraction.
• Surfaces with caps maintained a stable Cassie state with hexadecane, unlike vertical sidewall structures.
• Advancing contact angles were high and insensitive to Cassie fraction; receding angles closely followed Cassie equation predictions.

Conclusions:

• Overhanging cap structures enhance the stability of the Cassie state for superoleophobic surfaces.
• This improved stability comes with increased drop pinning compared to similar surfaces without caps.
• The findings offer new possibilities for designing robust liquid-repellent materials.