Manipulation of Micrometer-Scale Adhesion by Tuning Nanometer-Scale Surface Features

Abstract

This article demonstrates how the adhesion rates of micrometer-scale particles on a planar surface can be manipulated by nanometer-scale features on the latter. Here, approximately 500-nm-diameter spherical silica particles carrying a substantial and relatively uniform negative charge experienced competing attractions and repulsions as they approached and attempted to adhere to a negative planar silica surface carrying flat 11-nm-diameter patches of concentrated positive charge. The average spacing of these patches profoundly influenced the particle adhesion. For dense positive patch spacing on the planar collector, the particle adhesion was rapid, and the fundamental adhesion kinetics were masked by particle transport to the interface. For patch densities corresponding to a planar surface with net zero charge, particle adhesion was still rapid. Adhesion kinetics were observably reduced for patch spacings exceeding 20 nm and become slower with increased patch spacing. Ultimately, above a critical or threshold average patch spacing of 32 nm, no particle adhesion occurred. The presence of the threshold average patch spacing suggests that more than one positive surface patch was needed for particle capture under the particular conditions of this study. Furthermore, at the threshold, the length scales of the patch spacing and of the interactive surface area between the particle and the surface become similar: The concept of adhesion dominated by the matching of length scales is reminiscent of pattern recognition, even though the patch distribution on the collector is random in this work. Indeed, fluctuations play a critical role in these adhesion dynamics, hence the current behavior cannot be predicted by a mean field approach.

Deposition of colloid particles at heterogeneous and patterned surfaces

“…As can be seen, there was significant deposition of particles even in the case when the averaged zeta potential of the surface was of the same sign as the particle zeta potential. Similar observations were done in case of PAH covered mica [40] and the deposition of silica particles onto quartz sand modified to various degrees by the silanization procedure [39]. These observations contradict theoretical predictions stemming from the classical DLVO theory depicted by the dashed line in Fig.…”

“…15 seems quite universal, because it has also been observed in other polyelectrolyte/substrate systems, for example, for the PAH/mica system [40] or pDMAEMA/ silica system [39]. Because of similarities in chemical composition, it can be expected that analogous particle adsorption mechanism will appear in the case of surfaces covered by proteinous layers.…”

“…Especially reliable results have been obtained for quasi homogeneous surfaces, mostly mica modified by adsorption of silanes, aluminum compounds [16,17,23,25,27] or polyelectrolytes [35][36][37][38][39][40][41][42][43] using the diffusion [21,[24][25][26][44][45][46] or impinging-jet cells [11][12][13][14][15][16][17]23,25,27]. This was so because adsorbed particles can be ennumerated in real time using videomicroscopy or image analyzing systems allowing one to measure coordinates of thousands of particles at a prescribed time [19,23,25,27,40,41,[44][45][46].…”

“…From a practical point of view, however, especially interesting seems the problem of particle deposition at heterogeneous surfaces, covered by adsorption sites such as polyelectrolytes and polymers [35][36][37][38][39][40][41], proteins [42,43] or colloid nanoparticles [44][45][46][47].…”

Hydrogen-Bonding-Driven Self-Assembly of PEGylated Organosilica Nanoparticles with Poly(acrylic acid) in Aqueous Solutions and in Layer-by-Layer Deposition at Solid Surfaces

“…[10][11][12] The typical size of organosilica particles synthesized using Stöber conditions is often greater than 500 nm. 6,7,9 The Stöber method was also used to generate mesoporous materials, where homo-or co-condensation of TEOS with other functional silanes was conducted in the presence of low molecular weight or polymeric surfactants as a template. 1,10,13 Fewer studies have reported the development of organosilica nanoparticles with sizes smaller than 200 nm.…”