Particle–Bubble Interactions: an Investigation of the Three-Phase Contact Line by Atomic Force Microscopy

[Image: see text] The dynamics of the three-phase contact line during particle–bubble interactions determine the stability of particle–bubble aggregates in flotation. The interaction of particles and sessile gas bubbles can be studied by colloidal probe atomic force microscopy (CP-AFM). This paper demonstrates a method to obtain the contact angle, the position of the three-phase contact line on the particle, and the bubble profile by utilizing the full information contained in AFM force–distance curves, i.e., force and CP-position information as well as the work done to move the three-phase contact line on the CP-particle. The proposed method does not require any assumption of a constant contact angle or a constant opening angle. This is achieved by the combined solution of the particle force balance and an expression for the work required to move the three-phase contact line over the colloid probe. The applicability to AFM force–distance measurements was demonstrated for the interaction of a hydrophobic SiO(2) or a hydrophobic Al(2)O(3) colloidal probe particle with sessile gas bubbles having radii between 45 and 80 μm.