Autonomous and 3D real-time multi-beam manipulation in a microfluidic environment.

The Generalized Phase Contrast (GPC) method of optical 3D manipulation has previously been used for controlled spatial manipulation of live biological specimen in real-time. These biological experiments were carried out over a time-span of several hours while an operator intermittently optimized the optical system. Here we present GPC-based optical micromanipulation in a microfluidic system where trapping experiments are computer-automated and thereby capable of running with only limited supervision. The system is able to dynamically detect living yeast cells using a computer-interfaced CCD camera, and respond to this by instantly creating traps at positions of the spotted cells streaming at flow velocities that would be difficult for a human operator to handle. With the added ability to control flow rates, experiments were also carried out to confirm the theoretically predicted axially dependent lateral stiffness of GPC-based optical traps.