Breaking one into three: surface-tension-driven droplet breakup in T-junctions

Abstract

Droplet breakup is an important phenomenon in the field of microfluidics to generate daughter droplets. In this work, a novel breakup regime in the widely studied T-junction geometry is reported, where the pinch-off occurs laterally in the two outlet channels, leading to the formation of three daughter droplets, rather than at the center of the junction for conventional T-junctions which leads to two daughter droplets. It is demonstrated that this new mechanism is driven by surface tension, and a design rule for the T-junction geometry is proposed. A model for low values of the capillary number Ca is developed to predict the formation and growth of an underlying carrier fluid pocket that accounts for this lateral breakup mechanism. At higher values of Ca, the conventional regime of central breakup becomes dominant again. The competition between the new and the conventional regime is explored. Altogether, this novel droplet formation method at T-junction provides the functionality of alternating droplet size and composition, which can be important for the design of new microfluidic tools.

High precision, high throughput generation of droplets containing single cells

“…In this paper, we presented an extremely simple method for deterministic single-cell encapsulation in droplets. Based on a newly discovered droplet instability, 34 we developed an automatic workflow using a cell triggered splitting phenomenon (CTS) to create smaller satellite droplets containing single cells, for downstream separation of the positive droplets. Also for the post-encapsulation droplet size-based sorting, Chabert et al 40 reported a different mechanism for inducing droplet size difference.…”

“…The proposed method is based on a recent observation of a new droplet splitting instability in microfluidic T junctions. 34 Due to this splitting instability that occurs naturally in microfluidic junctions of specific geometries, a concept of cell-triggered splitting (CTS) is developed to achieve the passive and deterministic single-cell encapsulation in droplets without synchronization. A high throughput, labelfree, cost-effective, and robust single-cell encapsulation method will be demonstrated in this paper.…”

High precision, high throughput generation of droplets containing single cells

“…At the start, a random cell encapsulation is performed using a standard flow focusing geometry with low cell density (λ = 0.1 − 0.2), producing mother droplets that are mostly empty or contain a single cell [12]. These droplets then flow through a T junction designed to implement droplet splitting instability conditions [34]. In this T junction, empty mother droplets are split in two, but mother droplets containing a cell induce a lateral splitting instability as described in [34], which creates one additional small satellite droplet containing the cell.…”

“…These droplets then flow through a T junction designed to implement droplet splitting instability conditions [34]. In this T junction, empty mother droplets are split in two, but mother droplets containing a cell induce a lateral splitting instability as described in [34], which creates one additional small satellite droplet containing the cell. As a result, two types of droplets are obtained after splitting: large empty droplets and small cell-loaded satellite droplets.…”

“…We recently reported the observation of a new droplet splitting instability in microfluidic T junctions [34]. Based on this droplet splitting instability phenomenon, we propose here a passive and deterministic single-cell droplet encapsulation method with high specificity and no cell loss.…”