Simulations and experimental demonstration of three different regimes of optofluidic manipulation.

It has been demonstrated that optically controlled microcurrents can be used to capture and move around a variety of microscopic objects ranging from cells and nanowires to whole live worms. Here, we present our findings on several new regimes of optofluidic manipulation that can be engineered using careful design of microcurrents. We theoretically optimize these regimes using COMSOL Multiphysics and present three sets of simulations and corresponding optofluidic experiments. In the first regime, we use local fluid heating to create a microcurrent with a symmetric toroid shape capturing particles in the center. In the second regime, the microcurrent shifts and tilts because external fluid flow is introduced into the microfluidic channel. In the third regime, the whole microfluidic channel is tilted, and the resulting microcurrent projects particles in a fan-like fashion. All three configurations provide interesting opportunities to manipulate small particles in fluid droplets and microfluidic channels.