Electrostatic transfer of conductive particles for the formation of liquid marbles-charge transfer behavior

The electrostatic method for liquid marble formation has shown great promise in allowing contactless particle delivery to pendent liquid droplets. However, size has been shown to be a significant limitation in the selection of suitable particles for this transfer process. Here we overcome this size limitation using conductive copper particles as small as 6 μm diameter, delivering them to a 5 μL pendent water droplet at applied voltages between 0.5 and 3.0 kV. An electrometer in the grounding circuit enabled calculation of the average charge on an individual particle during the transfer process, accounting for the movement of particles within the bed during extraction utilizing the analytical sphere and plate model proposed by Morrison. A new constant, δ, is proposed to compensate for the dynamic charging that takes place during this process and nonuniformity in particle morphology. Using this constant a particle and mass transfer rate was calculated, demonstrating that smaller particles, once extracted from the bed, transfer at a faster rate than larger particles.