Berlin 2018 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 64: Nanostructures, Nanostructuring and Nanosized Soft Matter II
CPP 64.7: Vortrag
Donnerstag, 15. März 2018, 11:15–11:30, PC 203
Time resolved analysis of a Brownian motor — •Christian Schwemmer1, Stefan Fringes1,2, Urs Dürig1,3, and Armin Knoll1 — 1IBM Research - Zurich, Switzerland — 2Institute of Physical Chemistry, University of Zurich, Switzerland — 3SwissLitho AG, Zurich, Switzerland
Artificial Brownian motors mimic the mechanism behind intracellular transport in nature [1] and enable a controlled transport of particles in a fluid [2]. In our implementation, we use a novel approach based
on geometry induced trapping [3] to define a ratchet shaped potential landscape inside a nanofluidic slit. By applying a zero-mean AC electric field across the slit, we observed transport of 60 nm gold nano particles at drift speeds of 50 µm/s. The high temporal resolution of our experimental setup allowed us to measure the probability density in-situ and its temporal evolution with sub millisecond resolution. We observed current reversal at 250 Hz, an effect predicted more than 20 years ago [4], illustrating the nonlinear character of the motor. Comparison with a parameter-free theoretical model based on the Fokker-Planck equation shows excellent agreement. Using the model we traced the origin of the current reversal to the asymmetric, almost static probability density distribution at high frequencies, which leads to a faster increase of the backward current after switching the field direction.
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