Periodic forcing of a Brownian particle

Luc P. Faucheux, Gustavo Stolovitzky, Albert Libchaber

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96 Scopus citations


We study the effect on a Brownian particle (2 μm diameter polystyrene sphere in water) of an infrared optical tweezer moving in a circle. For a given potential depth of the optical trap, three different regimes for the particle motion are observed as a function of the trap velocity. For small velocity of the tweezer (typically <100 μm/s), the particle is trapped and moves with the beam. For intermediate velocities (between 100 μm/s and 3 mm/s), the particle escapes but is caught by the returning trap: its mean angular velocity scales asymptotically as the inverse of the trap rotation frequency. For large tweezer velocities (>3 mm/s), the particle diffuses along the circle but is confined in the radial direction. We describe these observations by a simple deterministic model. We justify the use of this model solving the corresponding Fokker-Planck equation.

Original languageEnglish
Pages (from-to)5239-5250
Number of pages12
JournalPhysical Review E
Issue number6
StatePublished - 1995
Externally publishedYes


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