Particle Surface Roughness as a Design Tool for Colloidal Systems

Abstract

Control over the surface roughness of colloidal particles offers exciting opportunities to tailor the properties and the processing of a broad range of soft matter systems. Moreover, identifying surface roughness as a design parameter reveals the possibility to connect seemingly distinct phenomena and materials via the role played by roughness effects. In this feature article, we concisely review some approaches to synthesize and characterize rough colloidal particles, with a focus on model spherical colloids. We then discuss the impact that surface roughness has on both the high-shear rheology of dense suspensions and the stabilization of Pickering emulsions. Commenting on developments of our own research, we aim to offer an original perspective for a property-oriented development of colloidal particles that transcends classical divisions between materials and processes toward innovative solutions.

Generalized Analysis Approach of the Profile Roughness by Electron Microscopy with the Example of Hierarchically Grown Polystyrene–Iron Oxide–Silica Core–Shell–Shell Particles

“…[32] Roughness has been extensively used as a parameter for surface characterization when employing atomic force microscopy (AFM). [33][34][35][36] In contrast, the literature that addresses this issue for nonplanar particles using SEM or TEM imaging is scarce and only qualitative. [37,38] Moreover, reported research in the literature on roughness analysis shows large differences in terms of methodology and reported results.…”

Flower‐Like Colloidal Particles through Precipitation Polymerization of Redox‐Responsive Liquid Crystals

“… [8] Shape‐anisotropy affects particle interaction with light, [9] leading to advances in plasmonic nanosensors, [10] opacifiers, [11] and switchable, full‐color reflective dispersions. [12] The shape and surface roughness [13] of colloidal particles alters their wetting characteristics, with applications in fluid repellent coatings,[ 14 , 15 , 16 ] and Pickering emulsions. [ 17 , 18 ] Particle geometry is also emerging as an important factor in biological cell interactions and uptake.…”

Synthesis of Rough Colloidal SU-8 Rods and Bananas via Nanoprecipitation

“…Controlling the surface roughness of colloidal particles is a powerful tool for designing materials with engineered rheological, wetting, and self-assembly properties . For instance, dense suspensions of rough colloidal spheres show shear thickening, i.e., a viscosity increase upon increasing shear rate, at lower shear rates than suspensions of colloidal spheres with a smooth surface. , This mechanical effect is explained in terms of interparticle frictional forces and finds applications in shock-absorbing materials .…”

“…The presence of surface asperities with a typical size larger than that of the depletant reduces the depletion attraction between particles or parts of the particles, leading, for example, to the selective formation of clusters depending on the particle roughness . To date, most of the studies addressing the relationship between microscopic surface roughness and macroscopic properties of soft matter systems have been performed with colloidal spheres. , However, the impact of surface roughness on materials formed by anisotropic colloidal particles, and therefore the interplay between surface roughness and shape, remains unexplored due to the lack of rough anisotropic colloidal particles.…”