Simultaneous separation of polydisperse particles using an asymmetric nonperiodic optical stripe pattern

We present simultaneous separation of polydisperse particles driven by an optical gradient force in the absence of microfluidic flow. The separation mechanism involves particle-size dependence of the potential landscape generated by a one-dimensional asymmetric optical stripe pattern. The outcome is that the particles align in different stacks according to their sizes. The dynamics of Brownian particles inside the optical potential landscapes are investigated theoretically and experimentally for various optical intensities and particle sizes. By introducing sequential changes in the optical profile, we also show that this technique allows semipassive arrangement of particles in arbitrary configurations.