London-van der Waals Force Field of a Chemically Patterned Surface To Enable Selective Adhesion

Abstract

The London-van der Waals (L-vdW) force between a particle and a surface strongly depends on the topography and the chemical properties of the interacting surfaces. Although a great deal of work has been done to understand the effect of topographical heterogeneity on the L-vdW adhesion, the role of chemical heterogeneity has been discussed only rarely. This study makes an attempt to quantify the magnitude and range of the L-vdW force acting on a spherical particle in the vicinity of a chemically patterned surface. Specifically, an ideal system of a smooth spherical particle approaching a surface composed of parallel stripes of chemically distinct materials with different Hamaker constants is considered. The L-vdW forces for such systems are determined by solving the London dispersion potential for the entire volumes of the adhering bodies from first principles, using Hamaker's microscopic approach. The computational results elucidate that a chemical interface can apply a tangential L-vdW force, in addition to the normal L-vdW force, on nearby particles. This can cause lateral motion of particles neighboring a chemically inhomogeneous surface. The magnitude of the tangential L-vdW force is found to be maximum when the particle is centered at the interface and shows a gradual drop as it moves away from this location. The magnitude and range of the tangential L-vdW force can be large for large colloidal particles in close contact with a chemically patterned surface whose materials have distinct Hamaker constants. This study suggests that the tangential L-vdW force field generated by a chemical interface can be utilized as a tool to manipulate the path of an approaching particle to facilitate selective adhesion.

Particle dispersion through porous media with heterogeneous attractions

“…Heterogeneous physicochemical attractions are challenging to characterize experimentally, [55][56][57] but commonly arise in practical settings in which the transported particles and porous medium exhibit spatial variations in composition and surface charge. 55,[58][59][60][61][62][63][64] Theoretical studies suggest that such variations can strongly influence the effective interactions between particle pairs and between particles and solid surfaces. 55,62,[65][66][67] Additionally, they have been shown to influence transport properties near 2-D or quasi-2-D surfaces.…”

“…55,[58][59][60][61][62][63][64] Theoretical studies suggest that such variations can strongly influence the effective interactions between particle pairs and between particles and solid surfaces. 55,62,[65][66][67] Additionally, they have been shown to influence transport properties near 2-D or quasi-2-D surfaces. 56,68,69 Nonetheless, the effects of heterogeneous interactions on the microscopic transport processes of particles through more complex 3-D porous media remain incompletely understood.…”