A fully reconfigurable two-dimensional (2D) rocking ratchet system createdwith holographic optical micromanipulation is presented. We can generateoptical potentials with the geometry of any Bravais lattice in 2D and introducea spatial asymmetry with arbitrary orientation. Nontrivial directed transportof Brownian particles along different directions is demonstrated numericallyand experimentally, including on-axis, perpendicular and oblique with respectto an unbiased ac driving. The most important aspect to define the currentdirection is shown to be the asymmetry and not the driving orientation, and yetwe show a system in which the asymmetry orientation of each potential well doesnot coincide with the transport direction, suggesting an additional symmetrybreaking as a result of a coupling with the lattice configuration. Ourexperimental device, due to its versatility, opens up a new range ofpossibilities in the study of nonequilibrium dynamics at the microscopic level.
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