Collection of suspended particles in a drop using low frequency vibration

Particle collection at low frequencies has been erstwhile demonstrated with dry particles and particles floating on the liquid surface. Nevertheless, the ability to collect suspended particles in a fluid offers arguably wider usage in the context of microfluidic or "lab-on-a-chip" systems. This is demonstrated here via an approach of vibrating a droplet to form resonant shapes on the liquid-gas interface. This results in particles ranging in size from 40 to 120 mu m being collected predominantly at the solid-liquid interface due to a hydrodynamic focusing mechanism that develops through multiple cycles.