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Particle Dispersion at Air-Water Interfaces: Role of Cleaning and Wettability
Khá-Î Tô1,2, R K Vishwakarma1, M M Bandi1
1Nonlinear and Non-Equilibrium Physics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan.
The Journal of Physical Chemistry. B
|April 22, 2026
Summary
The rapid spreading of powders on water is caused by impurities, not particle properties. Cleaning particles stops spreading, while adding surfactants restores it, revealing impurity-mediated Marangoni stresses.
Area of Science:
- Physical Chemistry
- Interface Science
- Fluid Dynamics
Background:
- Powders spread rapidly at air-water interfaces due to complex physicochemical mechanisms.
- Understanding particle dispersion is crucial for various applications.
Purpose of the Study:
- To experimentally investigate the driving forces behind rapid powder spreading at air-water interfaces.
- To elucidate the role of impurities and surface tension gradients in particle motion.
Main Methods:
- Utilized floating submillimetric particles to study dispersion dynamics.
- Conducted experiments with cleaned and impurity-reintroduced particles.
- Controlled surfactant concentrations to observe their effect on spreading.
Main Results:
- Rapid spreading (cm/s) was suppressed in cleaned particles, irrespective of wettability.
- Marangoni stresses from trace impurities were identified as the primary cause of fast spreading.
- Reintroducing surfactants restored the rapid dispersion, confirming impurity mediation.
Conclusions:
- The collective dispersion of powders at interfaces is primarily driven by impurity-induced Marangoni stresses.
- This clarifies the transport mechanism for particles at interfaces.
- Provides a basis for studying Marangoni-mediated particle motion.
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