11 September 2006 Linear and nonlinear microrheology of dense colloidal suspensions
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Abstract
The length and time scales accessible to optical tweezers make them an ideal tool for the examination of colloidal systems. Embedded high-refractive-index tracer particles in an index-matched hard sphere suspension provide 'handles' within the system to investigate the mechanical behaviour. Passive observations of the motion of a single probe particle give information about the linear response behaviour of the system, which can be linked to the macroscopic frequency-dependent viscous and elastic moduli of the suspension. Separate 'dragging' experiments allow observation of a sample's nonlinear response to an applied stress on a particle-by particle basis. Optical force measurements have given new data about the dynamics of phase transitions and particle interactions; an example in this study is the transition from liquid-like to solid-like behaviour, and the emergence of a yield stress and other effects attributable to nearest-neighbour caging effects. The forces needed to break such cages and the frequency of these cage breaking events are investigated in detail for systems close to the glass transition.
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Laurence Wilson, Laurence Wilson, Rut Besseling, Rut Besseling, Jochen Arlt, Jochen Arlt, Wilson C. K. Poon, Wilson C. K. Poon, } "Linear and nonlinear microrheology of dense colloidal suspensions", Proc. SPIE 6326, Optical Trapping and Optical Micromanipulation III, 63261P (11 September 2006); doi: 10.1117/12.681569; https://doi.org/10.1117/12.681569
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