Contact Angle Distribution of Particles at Fluid Interfaces

Abstract

Recent measurements have implied a distribution of interfacially adsorbed particles' contact angles; however, it has been impossible to measure statistically significant numbers for these contact angles noninvasively in situ. Using a new microscopy method that allows nanometer-scale resolution of particle's 3D positions on an interface, we have measured the contact angles for thousands of latex particles at an oil/water interface. Furthermore, these measurements are dynamic, allowing the observation of the particle contact angle with high temporal resolution, resulting in hundreds of thousands of individual contact angle measurements. The contact angle has been found to fit a normal distribution with a standard deviation of 19.3°, which is much larger than previously recorded. Furthermore, the technique used allows the effect of measurement error, constrained interfacial diffusion, and particle property variation on the contact angle distribution to be individually evaluated. Because of the ability to measure the contact angle noninvasively, the results provide previously unobtainable, unique data on the dynamics and distribution of the adsorbed particles' contact angle.

Interfacial Activity and Contact Angle of Homogeneous, Functionalized, and Janus Nanoparticles at the Water/Decane Interface

“…29 We assume that this scattering is due to the dependence of the CA upon the details of the different nanoparticles and their kinetics as they reach the interface. Furthermore, the narrower distribution of CAs for the PMMA-HPs might point to less CA variation of the homogeneous nanoparticles rather than the heterogeneous nanoparticles.…”

A non-equilibrium state diagram for liquid/fluid/particle mixtures

“…It must be acknowledged however, that it is difficult to quantify contact angles of small particles. 22,23 Thus, in this paper, contact angles are taken as a measure of relative wettability; y o 901 implies preferentialwetting of the particles by B, y 4 901 implies preferential wettability by the A fluid, and y = 901 indicates equal-wetting by A and B. 1 (a) Schematic of ternary composition diagram marking various regions.…”

Contact angle variation on single floating spheres and its impact on the stability analysis of floating particles

“…These findings display the complexity of the practical condition and demonstrate the CA hysteresis in a new perspective. A CA distribution is accepted to exist for different particles of the same size [26]. However, for a single particle, researchers do not consider the significance of the CA distribution and just take an average CA to characterize surfaces and their interactions instead of taking the surface heterogeneity and CA distribution into account.…”