Multistable interaction between a spherical Brownian particle and an air–water interface. Issue 4 (17th December 2019)

• Record Type: Journal Article
• Authors: Villa, Stefano; Stocco, Antonio; Blanc, Christophe; Nobili, Maurizio
• Is Part Of: Soft matter. Volume 16:Issue 4(2019)
• Page Start: 960
• Page End: 969
• Publication Date: 2019-12-17
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c9sm01472a
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : A novel multi-stable interaction between microparticles and fluid interfaces is measured pointing out the still unaccounted role of surface heterogeneities. Abstract : We report the measurement of the interaction energy between a charged Brownian polystyrene particle and an air–water interface. The interaction potential is obtained from the Boltzmann equation by tracking particle interface distance with a specifically designed Dual-Wave Reflection Interference Microscopy (DW-RIM) setup. The particle has two equilibrium positions located at few hundreds of nanometers from the interface. The farthest position is well accounted by a DLVO model complemented by gravity. The closest one, not predicted by current models, more frequently appears in water solutions at relatively high ions concentrations, when electrostatic interaction is screened out. It is accompanied by a frozen rotational diffusion dynamics that suggests an interacting potential dependent on particle orientation and stresses the decisive role played by particle surface heterogeneities. Building up on both such experimental results, the important role of air nanobubbles pinned on the particle interface is discussed.