Droplet on Soft Shuttle: Electrowetting-on-Dielectric Actuation of Small Droplets

Here, we introduce
the novel concept of a “soft shuttle”
for transportation, manipulation, and diffusion studies of small liquid
droplets using electrowetting on the dielectric mechanism. This method
enables manipulation of droplets several times smaller than the electrode
size and, importantly, minimizes evaporation, contamination, and exposure
of the sample to high voltages. We demonstrate various modes of droplet
loading, transporting, and unloading. Using advanced imaging processing
techniques, we obtained detailed information about the shuttle and
droplet centroids. Furthermore, varying water concentration on the
soft shuttle allows for modulation of the diffusion kinetics of samples
into the shuttle, which also can be controlled with soft shuttle actuation
velocity. We believe that this novel approach for the manipulation
of droplets will advance the field of droplet-based open microfluidics
and can be potentially useful for applications in biotechnology, diagnostics,
or analytical chemistry.