New method to measure interaction force between particle and air bubble/water droplet using a micro-Newton mechanics testing instrument

摘要

The interaction force between particle and air bubble/water droplet is the key to understand the underlying mechanism for mineral flotation. The most commonly used approach is colloidal probe atomic force microscopy (AFM), which usually operates in the nano-Newton range. This makes the quantification of the adhesion (capillary) force during retraction challenging, because the magnitude of the adhesion force is much higher than that of surface forces. In this short communication, a new instrument, the micro-mechanical testing machine (MMTM), was used to measure the interaction force between a micrometer glass bead and an air bubble/water droplet with both micro-Newton range and nano-Newton resolution. A single-axis capacitive microforce sensor based on interdigitated comb capacitors was equipped in the MMTM. Similar to the colloidal probe AFM, a hydrophilic glass bead with a diameter of 193 mu m was adhered to the end of the cantilever. The MMTM allows the simultaneous recording of the data of force, displacement, and time at a fixed velocity. The results showed that a strong jump-into contact and adhesion force were observed between the particle and water droplet. In contrast, a weaker jump-into and smaller adhesion force were observed between the bubble and particle. Based on the theoretical equation of the adhesion force, the equilibrium contact angle of the glass bead used was back calculated to be approximately 39.58 degrees, which is reasonable for its force behavior. The MMTM provides a flexible and alternative way to investigate the surface and interfacial forces in flotation systems. (C) 2020 Elsevier B.V. All rights reserved.