Controlled nucleation in evaporative crystallization using a confined-vapor driven solutal Marangoni effect

Area of Science:

• Physical Chemistry
• Materials Science
• Fluid Dynamics

Background:

• Evaporative crystallization in droplets often leads to undesirable coffee-ring effects, concentrating particles at the edge.
• Controlling nucleation site is crucial for tailoring crystalline morphology and material properties.

Purpose of the Study:

• To present a novel method for controlling surfactant crystallization nucleation location using vapor-driven solutal Marangoni effects.
• To suppress the conventional coffee-ring effect and achieve central particle accumulation.

Main Methods:

• Utilizing a binary mixture drop in a confined chamber to induce vapor-driven solutal Marangoni effects.
• Manipulating local surface tension via evaporated volatile vapors to generate inward flow.
• Testing surfactants with varying hydrocarbon chain lengths (CTAB > TTAB > DTAB).

Main Results:

• Successfully suppressed the evaporatively-driven capillary flow (coffee-ring effect).
• Achieved accumulation of suspended particles in the center of the droplet.
• Adjusted nucleation location from the droplet edge to the center for long-chain surfactants.

Conclusions:

• Vapor-driven solutal Marangoni effects offer a novel strategy for controlling evaporative crystallization nucleation.
• This method allows for precise control over particle accumulation and crystallization site.
• Potential applications in tailoring crystalline solid morphology and advanced material design.