Designing Plastrons for Underwater Bubble Capture: From Model Microstructures to Stochastic Nanostructures

Area of Science:

• Surface science
• Fluid dynamics
• Materials science

Background:

• Chemical defoamers and mechanical agitation are common methods for bubble and foam removal.
• Developing energy-passive, chemical-free bubble capture surfaces is vital for industrial applications like mineral flotation, wastewater treatment, and electrolysis.
• Super-liquid-repellent surfaces, termed plastrons, utilize textured topographies with gas domains to capture bubbles via coalescence.

Purpose of the Study:

• To investigate the influence of topographical feature size and gas fraction on the dynamics of bubble capture by plastrons.
• To elucidate the two-step mechanics of plastron-induced bubble coalescence: rupture and absorption.
• To provide design principles for efficient underwater bubble capture surfaces.

Main Methods:

• Investigated the effect of varying topographical feature sizes on bubble capture dynamics.
• Analyzed the impact of different gas fractions on bubble absorption.
• Examined bubble rupture initiation, location, and timing in relation to surface features.
• Studied the role of the liquid-solid contact line in bubble absorption post-rupture.

Main Results:

• Smaller topographical feature sizes were found to accelerate bubble rupture.
• Larger gas fractions significantly improved the absorption of bubbles.
• Bubble rupture initiates on solid domains, particularly near feature edges, but rupture time increases with higher solid fractions.
• The liquid-solid contact line dynamics post-rupture influence absorption rate and equilibrium.

Conclusions:

• Rational minimization of surface feature sizes is key for rapid bubble rupture.
• Optimizing gas fraction enhances bubble absorption efficiency.
• Understanding the interplay between feature size, gas fraction, and contact line dynamics is crucial for designing effective plastron surfaces for underwater bubble capture.