No abstract

Dynamic self-assembly of droplets, regular structure formation of moving deformable objects in a confinement environment is a challenging problem in nonlinear dynamics and engineering patterned structure. In the current work, we investigated how the local kinematic history affects the dynamic self-assembly of picoliter-sized droplets near the expansion regions in microfluidic devices. The local kinematic history was controlled by the shape of the expansion region and characterized using computational fluid dynamics. Sizecontrolled aqueous droplets in light mineral oil were continuously generated at T-junction microchannel and transported toward the expansion region. The fast dynamics of the droplets was tracked using high-speed video microscopy. We found three types of dynamic droplet arrays: 1D, 2D zigzag, and irregular. The orderdisorder transition was associated not only with the droplet size, but also with the controlled local kinematic history, which results in the transient deformation of droplet and droplet-droplet interactions. The present results provide us with insight into the dynamic self-assembly of droplets and could be a useful guide for practical applications of droplet-based microfluidics.