Deformation of double emulsions under conditions of flow cytometry hydrodynamic focusing

Abstract

Water-in-oil-in-water (w/o/w) microfluidics double emulsions offer a new route to compartmentalise reagents into isolated aqueous microenvironments while maintaining an aqueous carrier fluid phase; this enables compatibility with commercial flow cytometry systems such as fluorescence-activated cell sorting (FACS). Double emulsion (inner core) deformation under hydrodynamic focusing conditions that mimic the environment double emulsions experience in flow cytometry applications is of particular importance for droplet stability and cell viability. This paper reports on an experimental study of the dynamic deformation of aqueous cores of w/o/w double emulsions under hydrodynamic focusing, with the sheath flow directed at 45° to the sample flow. A number of factors affecting the inner core deformation and recovery were examined. Deformation was found to depend significantly on the core or shell viscosity, the droplet-to-sheath flow velocity ratio, and core and shell sizes. Core deformation was found to depend more on the type of surfactant rather concentration with high molecular weight surfactant exhibiting a negligible effect on deformation whereas low molecular weight surfactant enhancing deformation at low concentrations due to their lateral mobility at the interface.

Double emulsion flow cytometry with high-throughput single droplet isolation and nucleic acid recovery

“…enzymes, buffers, dyes, or antibodies) and surfactants to stabilize the W/O/W droplet architecture. 7,53,54 In the next stage (FACS phenotyping, Fig. 1B), DE droplets are quantitatively analyzed based on size and fluorescence and sorted via FACS into designated wells of a multi-well destination plate or other sort vessel.…”

“…7,45 Smaller droplet sizes lower DE droplet deformation during FACS and thus minimize likelihood of DE droplet breakage. 54 Devices were designed to produce W/O/W droplets significantly smaller than typical FACS nozzles (∼30 μm in diameter), with channel heights of 15 μm for the inner aqueous and oil phases (first flow focuser for W/O droplet generation) and 40 μm for outer aqueous phase (second flow focuser to wrap the oil shell with aqueous buffer and create the W/O/W droplet). Larger or smaller double emulsions can be generated with scaled versions of this device; we have generated DE droplet populations from 27.63-48.36 μm (see ESI †), all of which perform well with this workflow.…”

Mechanically activated artificial cell by using microfluidics

“…Control valve set 2 was designed to compress double emulsions inside the trapping chambers. Due to the fluid properties of the inner aqueous and middle oil phases, double emulsions deform easily when they experience different external flow fields4142. But when the external load is removed, double emulsions return to their original spherical shapes due to interfacial tension.…”

Microarrays for the study of compartmentalized microorganisms in alginate microbeads and (W/O/W) double emulsions

“…Water-in-oil single emulsions alone have several limitations that restrict their application as microcapsules for living materials. The oil carrier fluid does not allow continuous supply of nutrient or inducer molecules, and is incompatible with aqueous phase-based analysis such as flow cytometry, 30,47,48 for example. Therefore, double emulsions (W/O/W) with fluorinated oil shells (HFE7500, 3M®) were investigated as compartments for P. putida.…”