Snap-in dynamics of single particles to water drops

Abstract

The interaction between solid particles and gas-liquid interfaces is relevant in technological applications. Former studies did focus on detachment-dynamics of particles from thin liquid films or on attachment-dynamics of particles to gas bubbles. Here, we investigated snap-in dynamics of individual micron-sized particles to water drops by means of the colloidal probe technique. The snap-in time (∼0.1 ms) and the snap-in force of hydrophilic and hydrophobic particles were measured. The snap-in time increased with particle size regardless of wettability. The snap-in force increased with particle size and wettability. We show that the snap-in dynamics is dominated by capillarity and inertia.

Dynamic wetting: status and prospective of single particle based experiments and simulations

“…Variability may also arise from the dynamic nature of wetting. Initially, the capillary forces and hydrodynamics of a particle adsorbing to a fluid-fluid interface give wetting speeds in the order of a few m/s, while also longer timescale relaxation processes are observed with speeds as low as 10 À3 mm/s [38][39][40]. Such dynamic wetting effects should be taken into account when extracting values for the contact angle.…”

“…A description based on capillary forces and hydrodynamics results in exponential relaxation times with typical timescales of ms. Recently much longer timescales -several minutes, hours -were measured [38][39][40]. These observations call for the development of methods to quantify and model dynamic wetting effects on individual particles over a broad range of time and energy scales, and suitable for a wide range of particle types and fluid properties.…”

“…Recently it has been shown that the relaxation process of particles adsorbing into fluid-fluid interfaces can have a very long tail with contact line speeds as low as 10 À1 mm/s [38][39][40]. A description based on capillary forces and hydrodynamic friction predicts initial speeds in the order of a few m/s and relaxation times in the order of ms [38,41].…”

Detachment of particles and particle clusters from liquid/liquid interfaces

“…Later on, the dynamics of attachment (snap in) or detachment was studied in more detail. When a particle with a diameter of the order of 100 lm snaps in at the interface of a low viscosity-liquid such as water and a gas, its dynamics is usually governed by the interplay of capillary and inertial forces [14]. For particles attaching to liquid/liquid interfaces, the fast initial dynamics may be followed by an extremely slow process (on a time scale of days or even months) during which the particle assumes its final configuration at the interface.…”

Pinned down

“…Nevertheless, the results are consistent with a growing body of work showing -in the same, indirect way -that nanoscale heterogeneities do exist in colloids and are important for understanding their behaviour at fluid interfaces. In fact, recent experiments have shown that the attractive interactions between particles at interfaces 6 , as well as the relaxation rates of particles that breach an interface 7,8 , appear to be governed by surface defects. And because colloids typically have surface groups that keep the particles from aggregating, surface defects and contact-line pinning may be inherent features of colloidal systems.…”