Dynamics of droplet formation at T-shaped nozzles with elastic feed lines

Abstract

We describe the formation of water in oil droplets, which are commonly used in lab-on-a-chip systems for sample generation and dosing, at microfluidic Tshaped nozzles from elastic feed lines. A narrow nozzle forms a barrier for a liquid-liquid interface, such that pressure can build up behind the nozzle up to a critical pressure. Above this critical pressure, the liquid bursts into the main channel. Build-up of pressure is possible when the fluid before the nozzle is compressible or when the channel that leads to the nozzle is elastic. We explore the value of the critical pressure and the time required to achieve it. We describe the fluid flow of the sudden burst, globally in terms of flow rate into the channel and spatially resolved in terms of flow fields measured using micro-PIV. A total of three different stages-the lag phase, a spill out phase, and a linear growth phase-can be clearly discriminated during droplet formation. The lag time linearly scales with the curvature of the interface inside the nozzle and is inversly proportional to the flow rate of the dispersed phase. A complete overview of the evolution of the growth of droplets and the internal flow structure is provided in the digital supplement.

Viscoelasticity of blood and viscoelastic blood analogues for use in polydymethylsiloxane in vitro models of the circulatory system

“…In fact, to choose an adequate fluid for a particular application one has to consider, in addition to the refractive index and the fluid rheology, optical transparency, density, material compatibility, chemical stability, safety, and price. 25,26 In microfluidics, polydimethylsiloxane (PDMS) is one of the most widely used polymers to manufacture channels because of its transparency at optically visible wavelengths, biocompatibility, low autofluorescence, low cost, deformability and ability to mold easily among other advantages, which make this polymer a good candidate for manufacturing model vessels to study the dynamics of vascular diseases. [27][28][29] In this work, we develop transparent non-Newtonian blood analogues that exhibit rheological behavior under shear and extension very similar to real whole blood.…”

Picoliter Well Array Chip-Based Digital Recombinase Polymerase Amplification for Absolute Quantification of Nucleic Acids

“…Thus, after dispensing the reagent effectively, there was lesser residual liquid on the surface for reducing the opportunity of cross- contamination [73]. To produce a large number of monodispersed droplets, the scraping time (~5 s) is much shorter than that of other microdroplet techniques, in which droplets are commonly produced sequentially by T-junctions or flow [37][38][39][40][41]. Current digital droplet systems take considerable time for droplet production, which leads to amplification in the bulk solution.…”

“…Current droplet-based approaches also require pumping equipment and an external rapid readout device. To ensure a homogeneous droplet size distribution, the flow rate of droplet production by T-junctions [37,38] or flow focusing [39][40][41] must be precisely controlled. Moreover, all of these dPCR methods still require thermal cycling and accurate temperature control.…”

Droplet‐based microfluidics for microtoxicological studies

“…Droplets can be generated and processed easily in microfluidic systems [6]. The volumes of droplet can be adapted between the lower microliter and the femtoliter range, which can be formed with high reproducibility and homogeneity in size and composition [7][8][9][10]. In addition, they can be stored and transported [11][12][13], monitored [14,15], and manipulated by droplet fusion [16][17][18][19], splitting [20,21], switching [21][22][23], and sorting [24][25][26].…”