Dielectrophoretic Trapping of a Floating Liquid Marble

A liquid marble, a liquid droplet coated with hydrophobic powder, is an emerging digital microfluidic platform. It can potentially serve as a mixer or reactor for chemical and biological assays in the microscale. Automated manipulation of liquid marbles is essential for the implementation of more microfluidic functions in the technology platform of "lab in a marble". We report the analytical and experimental results of trapping a floating liquid marble using dielectrophoresis in a nonuniform electric field. Liquid marbles with volumes ranging from 5 to 50μL are effectively trapped by the dielectrophoretic force from a horizontal distance ranging from 10 to 60 mm and under an applied voltage ranging from 1.6 to 5 kV. A one-dimensional analytical model is then proposed for the trapping process and agrees well with experimental data. Finally, based on the relationship between the static friction coefficient and the Bond number of a floating liquid marble, an operation map is derived for successful trapping of the liquid marble, providing a better insight into controlled manipulation of liquid marbles.