Micromachined linear brownian motor: Net-unidirectional transport of nanobeads by tamed brownian motion with electrostatic rectification

This paper reports for the first time on net-unidirectional transport of nanobeads by Brownian motion using a periodic 3-phase electrostatic rectification. The transportation of beads is performed in 1 mum deep, 2 or 3 mum wide PDMS microchannels, which constrain three dimensional random motion of nanobeads into ID fluctuation, so-called tamed Brownian motion. 3 mum wide and 2 mum separated ITO electrodes are fabricated by lift-off process on a 24 x 36 mm² coverglass, and a previously fabricated PDMS sheet with microchannels and processed for inlets is aligned and sealed with the electrodes. Diluted fluorescent nanobead, 500 nm in diameter, solution is introduced and equilibrium of the flow is awaited. Electrostatic rectification observations are performed by an inverted microscope. Rectified net- unidirectional transport of nanobeads is achieved at 200 mVpp and 400 mVpp at 1 MHz. 2 different beads are transported along the channel over 20 and 10 mum, respectively, in about 100 seconds, while other bead just wandered around in the same microchannel.