We tracked the adsorption of clay particles on an optically trapped Latex bead and showed that the adsorption mechanism, which is driven initially by non-electrostatic dispersion forces, is  eventually dominated by screened electrostatic interactions with increase in age of the clay suspension 

We applied oscillatory shear strains to a Latex bead trapped in an aging clay gel and showed that the frequency-dependent elastic and viscous moduli extracted from these microrheology experiments are much smaller than the moduli extracted from bulk rheology experiments