Europhys. Lett.
Volume 67, Number 3, August 2004
Page(s) 477 - 483
Section Interdisciplinary physics and related areas of science and technology
Published online 01 July 2004
Europhys. Lett., 67 (3), pp. 477-483 (2004)
DOI: 10.1209/epl/i2004-10075-y

Forced motion of a probe particle near the colloidal glass transition

P. 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 $\phi_{\ab{g}}$. For dense liquid-like samples near $\phi_{\ab{g}}$, 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 $\phi_{\ab{g}}$ 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