Anisotropic memory effects in confined colloidal diffusion.
The motion of an optically trapped sphere constrained by the vicinity of a wall is investigated at times where hydrodynamic memory is significant. First, we quantify, in bulk, the influence of confinement arising from the trapping potential on the sphere's velocity autocorrelation function C(t). Next, we study the splitting of C(t) into C_{parallel}(t) and C_{perpendicular}(t), when the sphere is approached towards a surface. Thereby, we monitor the crossover from a slow t{-3/2} long-time tail, away from the wall, to a faster t{-5/2} decay, due to the subtle interplay between hydrodynamic backflow and wall effects. Finally, we discuss the resulting asymmetric time-dependent diffusion coefficients.
Jeney
Sylvia
S
Institut de Physique de la Matière Complexe, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland. sylvia.jeney@epfl.ch
Lukić
Branimir
B
Kraus
Jonas A
JA
Franosch
Thomas
T
Forró
László
L
D016880:Anisotropy; D003102:Colloids / Q000737:chemistry*; D004058:Diffusion; D046210:Microfluidic Analytical Techniques; D008956:Models, Chemical
D003102:Colloids