Forced motion of a probe particle near the colloidal glass transitionP. Habdas, D. Schaar, A. C. Levitt and E. R. Weeks
Physics Department, Emory University - Atlanta, GA 30322, USA
(Received 22 January 2004; accepted in final form 19 May 2004)
We use confocal microscopy to study the motion of a magnetic bead in a dense colloidal suspension, near the colloidal glass transition volume fraction . For dense liquid-like samples near , below a threshold force the magnetic bead exhibits only localized caged motion. Above this force, the bead is pulled with a fluctuating velocity. The relationship between force and velocity becomes increasingly nonlinear as is approached. The threshold force and nonlinear drag force vary strongly with the volume fraction, while the velocity fluctuations do not change near the transition.
82.70.Dd - Colloids.
64.70.Pf - Glass transitions.
61.43.Fs - Glasses.
© EDP Sciences 2004