Low-cost optical manipulation using hanging droplets of PDMS

Abstract

We propose and demonstrate a low-cost optical micromanipulation system that makes use of simple microfabricated components coupled to a smartphone camera for imaging. Layering hanging droplets of polydimethylsiloxane (PDMS) on microscope coverslips, and curing with a 100 W bulb, creates lenses capable of optical trapping. Optically trapped 3.93 μm silica beads were imaged with a second hanging droplet lens, doped with 1400 μg mL⁻¹ Sudan II dye. Through doping, a lens with an integrated long-pass filter that effectively blocks the 532 nm trapping light was produced. Illumination was provided by shining a lamp into polystyrene foam packaging, perpendicular to the imaging path, producing a diffuse light source. We observed two dimensional trapping and report a Q value of ∼8.9 × 10⁻³. The techniques here are an addition to the growing body of work on low cost and adaptable microfluidics.