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arXiv · 1805.03993

Experimental observation of current reversal in a rocking Brownian motor

Christian Schwemmer·Stefan Fringes·Urs Duerig·Yu Kyoung Ryu Cho·Armin W. Knoll
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Abstract

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.

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Christian Schwemmer, Stefan Fringes, Urs Duerig, Yu Kyoung Ryu Cho, Armin W. Knoll. 2018-07-23. Experimental observation of current reversal in a rocking Brownian motor. https://doi.org/10.1103/physrevlett.121.104102

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