Speed performance and control of a micromachined linear brownian motor

We report on fabrication and experimental characterization of a linear Brownian motor with a periodic 3-phase electrostatic rectification for unidirectional transport of nanobeads in microfluidic channels. The transport of the beads is performed in 1 mum deep, 2 mum wide PDMS microchannels, which constrain three-dimensional random motion of nanobeads into ID fluctuation, so-called tamed Brownian motion. 2 mum wide and 4 mum separated ITO electrodes are fabricated by lift-off process on a 24x36 mm² coverglass. After planarization of the surface, a previously fabricated PDMS sheet with microchannels is aligned and sealed with the electrodes. Diluted fluorescent nanobead suspension, 1:1000 and 500 nm in diameter, is introduced and equilibrium of the flow is awaited. Experimental results reveal the influence of electrode spacing, switching sequence (excitation time and Brownian time or diffusion time) and viscosity on the transportation and speed performance of the motor. Average speed is dependent on the switching sequence and it peaks around the expected diffusion time of the particles between electrodes.