Microrheology of a sticking transition

Condensed Matter journal club

Microrheology of a sticking transition

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The phenomenon of sticking of one object to another, which drastically reduces their relative motion, is ubiquitous in nature. We have studied the sticking process of a colloid, suspended in a fluid medium by an optical tweezer, to a rigid substrate. The evolution of the frictional coupling between the two as a function of their separation is detected by the diffusivity of the particle and also by its phase-sensitive response to an in-plane external oscillatory drive applied to the substrate. On contact, the coupling changes abruptly from viscous to elastic for a rigid silica particle, whereas it evolves slowly with time, similar to ageing in glassy systems, for a soft and deformable polystyrene particle. Depending on the relative strengths of the particle–substrate interaction, the tweezer potential and the external drive, three regimes of dynamics—stuck, ageing and non-stuck—are observed in the dynamical phase diagram.
href={http://dx.doi.org/10.1038/nphys1105}>Nature Phys. 4 960-966 (2008)


P. Sharma, S. Ghosh and S. Bhattacharya