We report an on-chip in-plane particle manipulator that utilizes a tunable Liquid gradient Refractive Index (L-GRIN) optofluidic microlens to optically control the pushing the particles/cells. We demonstrate light focusing within liquid medium via control of flow rates of CaCl2 and De-ionized (DI) water in a side-by-side co-injected fluid configuration thus controlling the focal length of the L-GRIN lens. Furthermore, refractive index profile can also be tailored by meticulous control of flow conditions thus causing the laser to swing. Utilizing these two degrees of freedom for laser, we demonstrate particle pushing mechanism by optical scattering force in these two modes. In the focusing mode, polystyrene beads (PS) are pushed within a chamber, thus devoiding a region free of beads, pushing them along optical axis direction away from the focal point, within a chamber. Utilizing the argon laser, particle velocity is controlled via laser input power. The swing mode, in a similar fashion, has been demonstrated to devoid a region in a chamber filled with PS beads, in sweep mode. Such work provides a new aspect of LGRIN lens to optically manipulate and push particles as well as cells thus providing a versatile patterning technique for a variety of biological and lab-on-chip applications.

© 2011 Optical Society of America

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