Fig. 1: Experimental set-up for inferring interparticle interactions in 2-d colloidal suspensions.
From: Chemical control of colloidal self-assembly driven by the electrosolvation force
a, b Schematic representation of a cluster of spheres of radius in a gravity-sedimented colloidal suspension, levitating above a silica coverglass, at an interparticle separation \(r\) and intersurface separation \(x\). Particles are imaged using bright field microscopy (see Experimental methods). c, d Particle coordinates are extracted from a microscope image using single particle tracking software65 and used to generate radial distribution profiles, \(g(r)\). e Digitised microscopy image where particles are represented as coloured discs of uniform diameter \(2R\) on a black background. Like-charged colloidal particles can be observed to form stable, slowly reorganising hexagonally close-packed (hcp) clusters in solution. Scale bar 10 μm. f Brownian dynamics simulations are used to infer a pair-interaction potential, \(U(x)\), characterised by an attractive minimum of depth \(w,\) and location \({x}_{\min }\), capable of reproducing the experimentally observed \(g(r)\) (see BD Simulation methods). Inferred interaction strengths \( |w| \approx 5 \, {{\rm{k}}}_{{\rm{B}}} T\) are typical for strongly clustering systems, as shown here for positively charged NH2 particles suspended in 1-octanol.
