Article abstract
Nature Physics
Published online: 26 October 2008 | doi:10.1038/nphys1105
Microrheology of a sticking transition
Prerna Sharma, Shankar Ghosh & S. Bhattacharya
Abstract
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.
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400-005, India
Correspondence to: Shankar Ghosh e-mail: sghosh@tifr.res.in
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