Particle capture via discrete binding elements: systematic variations in binding energy for randomly distributed nanoscale surface features.
This work examines how the binding strength of surface-immobilized "stickers" (representative of receptors or, in nonbiological systems, chemical heterogeneities) influences the adhesion between surfaces that are otherwise repulsive. The study focuses on a series of surfaces designed with fixed average adhesive energy per unit area and demonstrates quantitatively how a redistribution of the adhesive functionality into progressively larger clusters (stronger stickers) increases the probability of adhesive events. The work employs an electrostatic model system: relatively uniform, negative 1 μm silica spheres flow gently over negative silica flats. The flats contain small amounts of randomly positioned nanoscale cationic patches. The silica-silica interaction is repulsive; however, the cationic patches (present at sufficiently low levels that the overall surface charge remains substantially negative) produce local attractions. In this study, the attractions are relatively weak so that multiple patches engage to capture flowing particles. Experiments reveal an adhesion signature characteristic of a renormalized random distribution when the sticker strength is increased at an overall fixed binding strength per unit area of surface. The form of the particle capture curves are in good quantitative agreement with a simple model that assumes only a fixed adhesion energy needed for particle capture. Aside from the quantitative details that provide a simple formalism for anticipating particle adhesion, this work demonstrates how increasing the heterogeneities in the surface functionality can cause a system to go from being nonadhesive to becoming strongly adhesive. Indeed, systems containing small amounts of discretized adhesive functionality are always more adhesive than systems in which the same functionality is distributed uniformly over the surface (the mean field scenario).
Department of Polymer Science and Engineering, University of Massachusetts, 120 Governor's Drive, Amherst, Massachusetts 01003, United States.
Surachate
S
Kalasin
Surangkhana
S
Martwiset
E Bryan
EB
Coughlin
Maria M
MM
Santore
D000269:Adhesives / Q000737:chemistry; D000327:Adsorption; D008689:Methacrylates / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry*; D009757:Nylons / Q000737:chemistry; D011336:Probability; D013499:Surface Properties; D013816:Thermodynamics
D000269:Adhesives; D008689:Methacrylates; D009757:Nylons; C407037:poly(2-(dimethylamino)ethyl methacrylate)