Reciprocating Oscillation of a Floating Ferrofluid Marble Triggered by Magnetic Fields

Liquid marbles have the potential for microfluidic transport,
medical
diagnostics, and chemical analysis due to their negligible stickiness,
environmental independence, and excellent mobility. Here, we report
a non-contact manipulation strategy to arouse a reciprocating oscillation
of ferrofluid marbles floating on the water surface, which can be
used as microreactors. We experimentally investigated the quantitative
relationship between the oscillation behavior, the applied magnetic
field parameters, and the field regulation mechanism. The variables,
including the magnetic field strength, marble volume, and switching
period, are vital in determining the final state. The oscillation
can be separated into three stages: transitional movement, compressive
deformation, and rebound, before entering the next cycle. Accordingly,
we created a manipulation technique for improving the mixing of inner
reactants inside this marble container by remote-controlled shaking
after optimizing with an oscillation model.