Dynamics of high viscosity contrast confluent microfluidic flows

Abstract

The laminar nature of microfluidic flows is most elegantly demonstrated via the confluence of two fluids forming two stable parallel flows within a single channel meeting at a highly stable interface. However, maintenance of laminar conditions can become complicated when there is a large viscosity contrast between the neighbouring flows leading to unique instability patterns along their interface. Here, we study the dynamics of high viscosity contrast confluent flows – specifically a core flow made of highly viscous glycerol confined by sheath flows made of water within a microfluidic flow focusing system. Our experiments indicate the formation of tapered core structures along the middle of the channel. Increasing the sheath flow rate shortens the tapered core, and importantly induces local instability patterns along the interface of core-sheath flows. The dynamics of such tapered core structures is governed by the intensity of instability patterns and the length of the core, according to which the core structure can experience stable, disturbed, broken or oscillated regimes. We have studied the dynamics of tapered core structures under these regimes. In particular, we have analysed the amplitude and frequency of core displacements during the broken core and oscillating core regimes, which have not been investigated before.

Isolation of nuclei and downstream processing of cell-type-specific nuclei from micro-dissected mouse brain regions – techniques and caveats

“…The underlying reason is that microfluidics’ laminar nature is necessary to adequately detect particles during flow cytometry (as mentioned in EP1242804A2, Thermo Fisher). However, this is disturbed when the viscosity contrast between adjacent laminas is large (Kurdzinski et al, 2017), as in our case. Like other studies using sucrose gradient centrifugation methods, before sorting, the nuclei have to be re-centrifuged and resuspended in a less viscous solution like PBS (Dammer et al, 2013).…”

Mode Transition of Droplet Formation in a Semi-3D Flow-Focusing Microfluidic Droplet System

“…Three breakup modes will occur by adjusting pressure ratio and surfactant concentration. The interface becomes complicated when there is a large viscosity contrast between these two phases’ flows [ 18 ]. Comparing the droplet generation processes under the jetting mode, the droplet uniformity clearly worsens with increasing surfactant concentration.…”

Microscale hydrodynamic confinements: shaping liquids across length scales as a toolbox in life sciences

“…8). 83,113 For flow between parallel plates, lateral walls, if present, are spaced far apart compared to the distance between the bottom and top walls, and their impact on the flow pattern can be neglected. Furthermore, for flat parallel plates, the flow pattern in the z-direction (perpendicular to the parallel plates) is parabolic.…”

“…82 The situation can become complex for distinct fluids with large viscosity differences. 83 For confinements as depicted in Fig. 6a and b, theoretical models are also available to predict the inter-particle spacing for a sample being focused.…”