Droplet-based microfluidic systems generate, manipulate and control sub-microlitre droplets enclosed within an immiscible carrier fluid. Owing to a number of remarkable features, such as the ability to precisely control the chemical and biological payload of each droplet and to produce thousands of droplets per second, this technology is transforming how chemists and biologists perform high-throughput or massively parallel experiments. In this Primer, we initially introduce and describe the basic features of droplet-based microfluidic systems and key issues that should be considered when developing new chemical and biological workflows. We provide a critical evaluation of how droplet-based microfluidic systems should be manufactured and the importance of integrating appropriate detection technologies to probe the small analytical volumes that are representatives of the technology set. We then discuss issues related to data collection and management, providing guidelines on how large data sets should be processed and manipulated. Furthermore, we showcase some of the most successful and important applications of droplet-based systems in the biological and chemical sciences and consider issues that currently hinder progress in both technology development and application. Finally, we provide some opinion on future directions for the technology set and where its greatest impact will be felt in the coming years.
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The authors thank Y. Ding for assistance with the design and drawing of figures.
A.R.A. is a founder of Mission Bio and Fluent Bio. J.-C.B. is a founder and shareholder of Emulseo. D.D. is a founder and shareholder of Lattice Automation, Inc., Asimov Inc. and BioSens8 Inc. A.D.G. is a founder and shareholder of HiFiBiO Therapeutics, Biomillenia (now Design Pharmaceuticals), Cyprio and Minos Biosciences. All other authors declare no competing interests.
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The strength of the binding interaction between two molecules. Affinity can be described by the dissociation constant (KD) or by the standard free energy change (ΔG°): ΔG° = −RT ln KD where R is the gas constant and T is the absolute temperature.
A systematic and organized search for useful products derived from bioresources including plants, microorganisms and animals that can be developed further for commercialization or overall benefit to society.
- Capillary number
A dimensionless number used to quantify the ratio of viscous forces to capillary forces between two immiscible liquids.
A solid microcapsule formed by the self-assembly of colloidal particles at the interface of emulsion droplets.
- Interfacial tension
The force of attraction between molecules at the interface of two fluids.
- In vitro transcription
Allows template-directed synthesis of bespoke RNA molecules in microgram to milligram quantities outside the cellular environment.
- In vitro transcription translation
Coupled in vitro transcription and in vitro translation allowing protein synthesis outside the cellular environment, thus enabling rapid expression of small amounts of functional proteins.
- Lentiviral libraries
Libraries of genes cloned into vectors derived from lentiviruses, which infect by inserting DNA into the host cell genome and which can infect non-dividing cells.
An analysis approach that combines data from multiple omic sources, such as genomics, proteomics, transcriptomics, epigenomics and metabolomics, to study living systems in a concerted manner.
Opsonization is an immune process that uses opsonins (extracellular proteins) to mark foreign pathogens for elimination by phagocytes.
- Phage display
A method to select large libraries of genes encoding proteins, in which genes are inserted into a phage coat protein gene, resulting in phage particles with the protein displayed on the surface and the gene that encodes it inside the phage particle, generating a connection between genotype and phenotype.
- Poisson loading
An encapsulation strategy in which droplet occupancy follows a Poisson distribution.
An artificial vesicle in which the vesicle membrane is composed of amphiphilic block or triblock copolymers, with high stability and tunable size.
- Reynolds number
A dimensionless parameter quantifying the ratio of inertial forces to viscous forces in a system, useful in predicting whether a flow will be laminar or turbulent.
- Taylor cone
The shape of a fluid jet generated during electrospraying (such as during the sample ionization for mass spectrometry).
- Taylor dispersion
An effect in which shear acts to smear out the concentration distribution in the direction of the flow, enhancing the rate at which it spreads in that direction.
Describes the ability of a liquid to spread over a surface. It is normally quantified through measurement of the contact angle between the liquid and the surface.
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Moragues, T., Arguijo, D., Beneyton, T. et al. Droplet-based microfluidics. Nat Rev Methods Primers 3, 32 (2023). https://doi.org/10.1038/s43586-023-00212-3