A micro particle sampler using electrowetting-actuated droplet sweeping

We report a new micro particle sampler where airborne particles can be efficiently swept from a solid surface and sampled into a liquid medium using moving droplets actuated by the electrowetting principle. We successfully demonstrate that hydrophobic (8 μm-diameter Teflon-coated glass beads) as well as hydrophilic (8 μm-diameter glass beads) particles on a solid surface are swept and sampled into electrowetting-actuated droplets. In both cases, high sampling efficiencies are obtained, especially estimated over 95% for the hydrophilic particles based on image comparison. This sampler can be highly compatible and easily integrated with lab-on-a-chip systems for follow-up biological/chemical analyses, thereby realizing handheld fast-response environmental monitoring systems capable of directly detecting airborne bio-warfare agents such as anthrax.