Optically Activated Core Flow Shifting Within A Focused Flow

We report on the application of an optical beam to redirect sheathed micro-fluidic flow without direct interaction with the sample. The hydrodynamic properties of the sheath are locally modified due to optical heating, resulting in a spatial shift of the sample flow. We characterize this technique for a range of flow rates and demonstrate up to 100 mu m shift at peak flow velocities of 19 mm/s. We also model the temperature and viscosity changes, as well as the flow velocity profiles for a two-fluid flow with different viscosities. The calculated shifts in the flow profile correspond well with the measured shifts. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3623443]