  We report the breakup dynamics of a magnetically active droplet (ferrofluid
droplet) in a T-shaped LOC device under the modulation of a non-uniform
magnetic field. We adhere to high-speed imaging modalities for the experimental
quantification of the droplet splitting phenomena in the presence of a
non-uniform force field gradient, while the underlying phenomena is supported
by the numerical results in a qualitative manner as well. On reaching the
T-junction divergence, the droplet engulfs the intersection fully and
eventually deforms into the dumbbell-shaped form making its bulges to move
towards the branches of the junction. We observe that the asymmetric
distribution of the magnetic force lines, acting over the T-junction
divergence, induces an accelerating motion to the left moving bulge (since the
magnet is placed adjacent to the left branch). We show that the non-uniform
force field gradient allows the formation of a hump-like structure inside the
left moving bulge which triggers the onset of augmented convection in its flow
field. We reveal that this augmented internal convection developed in the left
moving volume/bulge, on getting coupled with the various involved time scales
of the flow field, lead to the asymmetric splitting of the droplet into two
sister droplets. Our analysis establishes that at the critical strength of the
applied forcing, as realized by the critical magnetic Bond number, the flow
time scale becomes minimum at the left branch of the channel, leading to the
formation of larger sized sister droplet therein. Inferences of the present
analysis, which focuses on the simple, wireless, robust and low-cost droplet
splitting mechanism, will provide a potential solution for rapid droplet
breakup, typically finds significant importance in point-of-care diagnostics.
