Colloidal particle deposition on microchannel walls, for attractive and repulsive surface potentials

Author(s)

Porto Santos, Tatiana ^{[1, 2]} ; Cunha, Rosiane Lopes ^[2] ; Tabeling, Patrick ^[1] ; Cejas, Cesare M. ^[1]

Affiliation

^[1] PSL Res Univ, ESPCI Paris, Inst Pierre Gilles Gennes IPGG, Nanostruct Lab, Microfluid, MEMS, CNRS, Chim Biol Innovat CBI, UMR 82, 6 Rue Jean Calvin, F-75005 Paris - France

^[2] Univ Estadual Campinas, Fac Food Engn, Dept Food Engn, Rua Monteiro Lobato 80, BR-13083862 Campinas - Brazil

• Document type: Journal article
• Source: Physical Chemistry Chemical Physics; v. 22, n. 30, p. 17236-17246, AUG 14 2020.
• Web of Science Citations: 1

Abstract

Surface interactions are an interplay of van der Waals adhesion forces with electrostatic charges. In colloidal deposition, at low ionic strengths, the Debye layer is sufficiently large to prevent particles from approaching the surface. It is only with the addition of higher salt concentrations, typically above 0.1 M, that surface charges are screened for interactions to take placeviavan der Waals-adhesion forces. This is true for repulsive charges, when both surfaces have similar charges and signs of the zeta potential are the same. However, with attractive charges, where zeta potential signs are opposite, the result is also opposite. By combining microfluidic experiments, theory, and numerical simulations, results show that when charges are attractive, particle deposition instead increases at low ionic strengths (at greater Debye lengths), at rates controlled by van der Waals forces but assisted by electrostatic forces. We propose a mechanism where particles approach the wall, mobilized by electrostatic attraction, up to a distance where van der Waals forces come into play, collecting the particles at the wall, which electrostatic forces alone are unable to achieve, owing to hindered diffusion. The present work thus allows us to understand the different mechanisms that govern deposition in the case where surface charges are opposite. (AU)

• FAPESP's process: 17/18109-0 - Development of an emulsion stability analyzer from microfluidics
• Grantee: Tatiana Porto dos Santos
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 19/07744-1 - Use of microfluidic devices to evaluate emulsion stability
• Grantee: Rosiane Lopes da Cunha
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/18103-4 - Systematic study of microchannels to evaluate coalescence in oil-in-water and water-in- oil emulsions
• Grantee: Tatiana Porto dos Santos
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate