Single step fabrication and characterization of PDMS micro lens and its use in optocapillary flow manipulation

We report single-step fabrication and characterization of PDMS microlens and demonstrate its use in optocapillary flow manipulation. Mixed PDMS droplets are dispensed over a thermally controlled Si substrate and cured to obtain microlenses. The spreading characteristics of sessile PDMS droplets are measured with time and substrate temperature. The gel-time of PDMS drops is studied for various substrate temperatures. The micro lenses are characterized based on the numerical aperture, focal length, f/number, optical transparency and spot size. Finally, micro lenses are used for focusing light from a low power IR laser for the manipulation of capillary flow in a microchannel.