Microstructure and micromechanics of hard spheres with short-range attraction

We study the microscopic mechanical response of colloidal gels, such as yielding, compression and~rearrangement, by manipulating single probe particles within the network. For this work,~we use fluorescent polymethylmethacrylate (PMMA)~dispersed in mixtures of decalin and cyclohexylbromide, with a refractive index and~density close to that of PMMA. The strength of attraction is controlled by the~concentration of a non-adsorbing polymer, polystyrene, which induces a depletion attraction between particles. In the presence of sufficiently strong attractive~forces, particles form a colloidal gel.~Confocal microscopy is used to~observe the structural evolution in real time.~This enables us to investigate the role of the local structure~and particle interactions in the elasticity of the network. Specifically, we identify local elastic and plastic deformations in gels, which~depend on the probe oscillation amplitude and strength of attractive interactions.