Multiple equilibria enables tunable wetting of droplets on patterned liquid surfaces

Area of Science:

• Surface science
• Fluid dynamics
• Materials science

Background:

• Patterning solid surfaces with controlled wettability is crucial for microfluidics, heat transfer, and printing.
• Solid surface roughness introduces limitations like contact-line pinning and friction, hindering droplet manipulation.
• Existing methods struggle to achieve both precise wettability control and surface smoothness.

Purpose of the Study:

• To introduce a novel experimental strategy and theoretical design principles for patterned liquid surfaces (PaLS).
• To demonstrate how PaLS combine controlled wettability with the ultrasmoothness of lubricant-infused surfaces.
• To explore the rich wetting behaviors and control mechanisms offered by PaLS.

Main Methods:

• Experimental fabrication of patterned liquid surfaces (PaLS) using lubricant-infused surface technology.
• Characterization of droplet behavior and wetting states on PaLS.
• Theoretical derivation of surface-averaged laws for apparent contact angle in different wetting states.

Main Results:

• PaLS exhibit 10 distinct wetting states, offering unprecedented control over droplet behavior.
• The apparent contact angle of droplets on PaLS can be tuned across the full wettability range.
• Contact-line pinning effects, common in solid surfaces, are eliminated on PaLS.
• Derived theoretical laws accurately predict experimental and simulation data for apparent contact angles.

Conclusions:

• PaLS provide a distinct and effective approach to surface patterning for droplet management.
• The unique properties of PaLS leverage fluid interactions with lubricant-impregnated surfaces.
• This technology has significant potential for applications requiring precise droplet control and manipulation.