title: Brownian motion: absolute negative particle mobility.
abstract: Noise effects in technological applications, far from being a nuisance, can be exploited with advantage - for example, unavoidable thermal fluctuations have found application in the transport and sorting of colloidal particles and biomolecules. Here we use a microfluidic system to demonstrate a paradoxical migration mechanism in which particles always move in a direction opposite to the net acting force ('absolute negative mobility') as a result of an interplay between thermal noise, a periodic and symmetric microstructure, and a biased alternating-current electric field. This counterintuitive phenomenon could be used for bioanalytical purposes, for example in the separation and fractionation of colloids, biological molecules and cells.
authors.affiliation: Experimental Biophysics & Applied Nanosciences, Bielefeld University, 33501 Bielefeld, Germany. dra.ros@physik.uni-bielefeld.de
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ros
authors.forename: Ralf
authors.initials: R
authors.lastname: Eichhorn
authors.forename: Jan
authors.initials: J
authors.lastname: Regtmeier
authors.forename: Thanh Tu
authors.initials: TT
authors.lastname: Duong
authors.forename: Peter
authors.initials: P
authors.lastname: Reimann
authors.forename: Dario
authors.initials: D
authors.lastname: Anselmetti