Experimental observation of current reversal in a rocking Brownian motor

A reversal of the particle current in rocking Brownian motors was predicted more than 20 years ago; however, an experimental verification and a deeper insight into the underlying mechanisms remained elusive. Here, we investigate the high frequency behaviour of a rocking Brownian motor for charged na...

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Bibliographic Details
Published in:arXiv.org 2018-07
Main Authors: Schwemmer, Christian, Fringes, Stefan, Duerig, Urs, Ryu Cho, Yu Kyoung, Knoll, Armin W
Format: Article
Language:English
Subjects:
Density
Fluidics
Fokker-Planck equation
Gold
High frequencies
Motors
Nanofluids
Nanoparticles
Spatial resolution
Time dependence
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Summary:A reversal of the particle current in rocking Brownian motors was predicted more than 20 years ago; however, an experimental verification and a deeper insight into the underlying mechanisms remained elusive. Here, we investigate the high frequency behaviour of a rocking Brownian motor for charged nanoparticles based on electrostatic interactions in a 3D shaped nanofluidic slit and electro-osmotic forcing of the particles. A sub ms temporal and \(\approx\,10\,\)nm spatial resolution of the 60 nm gold spheres allows us to measure the time-resolved and frequency dependent evolution of the particle probability density in-situ. At 250 Hz the particle current changes sign, in agreement with a theoretical model based on the time-dependent Fokker-Planck equation. From this fit-parameter free description and its excellent agreement with the observed behaviour, we trace the origin of the current reversal to the asymmetric and increasingly static probability density at high frequencies.
ISSN:2331-8422
DOI:10.48550/arxiv.1805.03993