Internal dynamics and elasticity of confined entropic gels

The internal dynamics and elasticity of colloidal gels formed via depletion in confined nearly hard-sphere mixtures are studied via particle-tracking measurements of the self part of the van Hove correlation function, which is found to decay exponentially in space and exhibit a scaling in terms of its first moment. The second moment, or mean-square particle displacement, exhibits a stretched-exponential decay to a plateau and provides a measure of the weak elastic modulus of the gel. A Fourier analysis of the real-space probability distribution yields the intermediate scattering function, which at fixed wave vector exhibits a stretched exponential decay to a nonzero plateau, reminiscent of dynamic behavior observed in a broad class of disordered systems.