Tunable coffee-ring effect on a superhydrophobic surface.

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• The coffee-ring effect (CRE) typically results in particle deposition at the edge of a drying droplet.
• Controlling CRE for patterned nanoparticle (NP) deposition remains a challenge.

Purpose of the Study:

• To achieve a tunable coffee-ring effect for patterned nanoparticle deposition.
• To design and investigate composite surfaces for controlled NP assembly.

Main Methods:

• Fabrication of a composite surface with superhydrophilic and superhydrophobic regions on a titanium substrate.
• Utilizing picosecond laser-induced periodic surface structures and micro-nano hierarchical structures to create low-adhesion superhydrophobic areas.
• Investigating nanoparticle deposition from suspension turbid liquid.

Main Results:

• Achieved tunable CRE on the designed composite surface.
• Demonstrated NP deposition in significantly reduced areas (0.045 mm², 265.56x smaller than hydrophilic surface).
• Obtained various deposition patterns including triangular, rectangular, and elliptical shapes, in addition to the traditional circular shape.
• Showcased controllable morphology of CRE with NPs in suspension liquid up to 1 mg/mL concentration.

Conclusions:

• The developed composite surface enables controllable morphology of the coffee-ring effect for patterned nanoparticle deposition.
• This technique offers maneuvering capability for nanoparticles in liquid suspension.
• The findings hold promise for applications in nanoparticle-printed circuit boards and site-specific drug delivery.