A modular approach for the generation, storage, mixing, and detection of droplet libraries for high throughput screening

Abstract

The desire to make microfluidic technology more accessible to the biological research community has led to the notion of "modular microfluidics", where users can build a fluidic system using a toolkit of building blocks. This paper applies a modular approach for performing droplet-based screening, including the four integral steps of library generation, storage, mixing, and optical interrogation. Commercially available cross-junctions are used for drop generation, flexible capillary tubing for storage, and tee-junctions for serial mixing. Optical interrogation of the drops is achieved using fiber-optic detection modules which can be incorporated inline at one or more points in the system. Modularity enables the user to hand-assemble systems for functional assays or applications. Three examples are shown: (1) a "mix and read" assay commonly used in high throughput screening (HTS); (2) generation of chemically distinct droplets using microfractionation in droplets (microFD); and (3) in situ encapsulation and culture of eukaryotes. Using components with IDs ranging from 150 microm to 1.5 mm, this approach can accommodate drop assays with volumes ranging from 2 nL to 2 microL, and storage densities ranging from 300 to 3000 drops per metre tubing. Generation rates are up to 200 drops per second and merging rates are up to 10 drops per second. The impact of length scale, carrier fluid viscosity, and flow rates on system performance is considered theoretically and illustratively using 2D CFD simulations. Due to its flexibility, the widespread availability of components, and some favorable material properties compared to PDMS, this approach can be a useful part of a researcher's toolkit for prototyping droplet-based assays.

Microfluidic platform for combinatorial synthesis in picolitre droplets

“…Automated robotic systems could be used to produce reagent A 1-m droplets 44 and load reagents B 1-n into nanolitre or microlitre reagent plugs separated by oil into PTFE tubing. [18][19][20][23][24][25] To mix larger libraries of A 1-m droplets (higher m value), multiple PEEK crosses or mechanical mixing 44 could be used. Furthermore, many droplets containing each reaction are produced; for the 21 member library here 10 6 droplets were produced for each reaction (at a rate of 2.3 kHz).…”

Microfluidics for cell-based high throughput screening platforms—A review

“…Trivedi et al [63] presented a hand-assembled microfluidic droplet system for cell based drug screening using polytetrafluorethylene (PTFE) tubing modules, see Fig. 11.…”

“…Reproduced with permission from Ref. [63]. liquid pipet chip, Zhou et al [69] developed a PDMS printing system controlled by pneumatic pump.…”

Progress of Microfluidics for Biology and Medicine

“…It is a generic, fast, and robust tool that can be used largescale screen and analysis of small samples. Recently, a modular approach to droplet-based screening was proposed, which included droplets library generation, storage, mixing, and optical detection [109]. …”