Dispensing Small Droplets with Low Generating Power

Abstract

Dispensed small droplets are widely used in analyses of small organisms in various bioapplications. The generating power used to induce "flying beads" of dispensed small droplets should be sufficiently low to guarantee the safety of the organisms. In this study, we fabricated carbon nanotube (CNT) nanobundles electroplated with gold nanoparticles. Small droplets were generated by the repulsive force in an ion-concentrated zone; in this region, the droplets were generated at lower voltages due to the higher ion concentration. The generating power was examined as a function of electrode diameter (0.6, 20, and 500 μm) and decreased significantly with electrode size, specifically 0.007 mW for the 0.6-μm-diameter electrode compared with 0.017 W for the 20-μm-diameter electrode. The beads expelled from the mother droplet at 0.007 mW had an initial velocity of ~2 m min −1 . This technique is expected to be particularly useful for the analysis of very small analytes.