Order and Chaos: Collective Behavior of Crowded Drops in Microfluidic Systems

Collective Behavior of Crowded Drops in Microfluidic Systems

Droplet microfluidics, in which micro-droplets serve as individual reactors, has enabled a wide range of high-throughput biochemical processes. Unlike solid wells typically used in current biochemical assays, droplets are subject to instability and can undergo breakup, especially under fast flow conditions. Although the physics of single drops has been studied extensively, the flow of crowded drops or concentrated emulsions, where droplet volume fraction exceeds 80 percent, is relatively unexplored in microfluidics. In this article and the related invited lecture from the 74th Annual Meeting o…

Eelectrokinetic turbulence and chaos in ionic migration and in microfluidic convection

Turbulence in the ionic migration and in the microfluidic electro-hydrodynamic convection (mixing) under constant and low-frequency external electric field has been studied using distributed chaos approach and notion of effective (turbulent) diffusivity. Results of corresponding laboratory experiments have been also used for this purpose. It is shown that for the migration and convection (mixing) under constant and low-frequency external electric field the turbulent power spectra have stretched exponential form $E(k) \propto \exp-(k/k_β)^{2/3}$. In the case of the microfluidic convection the d…

Origins of periodic and chaotic dynamics in microfluidic loop devices

Droplets moving in a microfluidic loop device exhibit both periodic and chaotic behaviors based on the inlet droplet spacing. We propose that the periodic behavior is an outcome of a dispersed phase conservation principle. This conservation principle translates into a droplet spacing conservation equation. Additionally, we define a simple technique to identify periodicity in experimental systems with input scatter. Aperiodic behavior is observed in the transition regions between different periodic behaviors. We propose that the cause for aperiodicity is the synchronization of timing between th…

非顺应性微流控网络中的涌现振荡与混沌

Emergent oscillations and chaos in non-compliant microfluidic networks

本文通过直接数值模拟与模态分析简化模型，证明非顺应性微流控网络在时间无关驱动压力下可因流体惯性自发产生流速振荡与混沌，并揭示了振荡起始、分岔、频率和振幅对驱动压力的依赖关系。

Simulation of Droplet Trains in Microfluidic Networks

In this work we show that in a microfluidic network and in low Reynolds numbers a system can be irreversible because of hysteresis effects.The network, which is employed in our simulations, is taken from recent experiments. The network consists of one loop connected to input and output pipes. A train of droplets enter the system at a uniform rate, but they may leave it in different patterns, e.g. periodic or even chaotic. The out put pattern depends on the time interval among the incoming droplets as well as the network geometry and for some parameters the system is not reversible.

微织构弹性流中共存的混沌与有序

Coexisting chaos and order in micro-textured elastic flows

本研究结合数值模拟与微流控实验，发现粘弹性流体在微柱阵列冠层上方流动时，弹性湍流与弹性波可共存，二者是粘弹性流动的互补表现，为生物和工程环境的运输调控提供了新机制。