In this work, we demonstrate an integrated microfluidic/photonic architecture for performing dynamic optofluidic trapping and transport of particles in the evanescent field of solid core waveguides. Our architecture consists of SU-8 polymer waveguides combined with soft lithography defined poly(dimethylsiloxane) (PDMS) microfluidic channels. The forces exerted by the evanescent field result in both the attraction of particles to the waveguide surface and propulsion in the direction of optical propagation both perpendicular and opposite to the direction of pressure-driven flow. We use a combination of theoretical and numerical analysis to calculate the particle trapping stability on a straight waveguide under microfluidic flow and provide estimates for the steady-state propulsion velocities. Velocities of 28 μm/s were achieved for 3 μm diameter polystyrene spheres with an estimated 53.5 mW of guided optical power at the trapping location. The particle-size dependence of the optical forces in such devices is also characterized.
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