Biomedical subjects

Ralf Eichhorn

Publications and source records attributed to Ralf Eichhorn.

4 recordsLinked to original sources

PubMed2005

Brownian motion: absolute negative particle mobility.

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.

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PubMed2004

Paradoxical nonlinear response of a Brownian particle.

We consider a Brownian particle in a "meandering" periodic potential when the ambient temperature is a periodically or stochastically varying function of time. Though far from equilibrium, the linear response of the particle to an external static force is exactly the same as in the equilibrium case, i.e., for constant temperature. Even more surprising is the nonlinear response: the particle slows down and then even starts to move in the direction opposite to the applied force.

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PubMed2002

Paradoxical motion of a single Brownian particle: absolute negative mobility.

We consider a single, classical Brownian particle in a spatially symmetric periodic system far from thermal equilibrium, which can be readily realized experimentally. Upon application of an external static force F, the average particle velocity is negative for F>0 and positive for F<0 (absolute negative mobility). The various physical mechanisms responsible for such a paradoxical effect are identified, leading to analytical approximations that are in good agreement with numerical simulations.

Journal Article↗

PubMed2002

Brownian motion exhibiting absolute negative mobility.

We consider a single Brownian particle in a spatially symmetric, periodic system far from thermal equilibrium. This setup can be readily realized experimentally. Upon application of an external static force F, the average particle velocity is negative for F>0 and positive for F<0 (absolute negative mobility).

Journal Article↗