Dynamic Effects on the Mobilization of a Deposited Nanoparticle by a Moving Liquid-Liquid Interface

Abstract

Using molecular dynamics simulations, we investigate the fate of a nanoparticle deposited on a solid surface as a liquid-liquid interface moves past it, depending on the wetting of the solid by the two liquids and the magnitude of the driving force. Interfacial pinning is observed below a critical value of the driving force. Above the critical driving force for pinning and for large contact angle value we observe stick-slip motion, with intermittent interfacial pinning and particle sliding at the interface. At low contact angles we observe that particle rolling precedes detachment, which indicates the importance of dynamic effects not present in static models. The findings in this work indicate that particle mobilization and removal efficiencies originating in dynamic liquid-liquid interfaces can be significantly underestimated by static models.

Capillary Torque on a Particle Rotating at an Interface

“…To gain further insights into the implications of the capillary torque, we consider two special cases: (1) when the particle rotates about its static equilibrium position and (2) when the particle is surrounded by a small liquid meniscus on a flat surface. Recent studies have argued that rotation is a relevant factor that needs to be considered when removing particles from surfaces by liquid–air interfaces (e.g., a drop). , In the following, we quantitatively show that capillary torque is also important when describing particles in Brownian motion at an interface and when considering the rolling of wet particles on surfaces.…”

“…Recent studies have argued that rotation is a relevant factor that needs to be considered when removing particles from surfaces by liquid−air interfaces (e.g., a drop). 24,25 In the following, we quantitatively show that capillary torque is also important when describing particles in Brownian motion at an interface and when considering the rolling of wet particles on surfaces.…”

Capillary detachment of a microparticle from a liquid–liquid interface

“…36,37,68 During the detachment process, two different phenomena for a three-phase contact line may arise: Either the contact line remains stationary until a threshold force is exceeded (i.e. the contact line is pinned) 15,68 or it slides continuously over the particle (i.e. the contact line is not pinned).…”

“…Microscale particles at liquid-liquid interfaces are found in a host of applications, for example in Pickering emulsions, [1][2][3] interfacial stabilizers, [4][5][6][7] colloidal particle assemblies, [8][9][10][11][12][13][14][15] and capillary suspensions. [16][17][18] For Pickering emulsions, particles are used to stabilize two immiscible fluids, like oil and water.…”

Janus Particles at Fluid Interfaces: Stability and Interfacial Rheology

“…The field of rheology examines the deformation and flow of matter in response to applied disturbances. Interfacial rheology pertains to techniques investigating the behavior of interfaces (2D) to inform us on the role of surface-active species in the resulting properties of interfacial systems [ 99 , 100 , 101 ]. For instance, in the dilational rheology realm, particle-laden interfaces have shown a dominant elastic behavior in presence of fumed silica particles [ 102 ].…”