A reproducible approach to the assembly of microcapillaries for double emulsion production

Mark A. Levenstein,Ciara S. Mc Nally,William J. Marchant,Fiona C. Meldrum,Lukmaan A. Bawazer,Xiuqing Gong,Nikil Kapur

doi:10.1007/s10404-016-1806-2

Abstract

Double emulsions attract considerable interest for their utility in applications as diverse as drug delivery, contrast agents, and compartmentalizing analytes for fluorescence-activated cell sorting. Microfluidic platforms offer a particularly elegant approach to generating these structures, but the construction of devices to provide reproducible and stable production of double emulsions remains challenging. PDMS-based systems require specialized surface treatments that are difficult to implement and lack long-term stability, and current glass microcapillary systems, while offering some advantages, lack flexible and reproducible methods for capillary alignment. This article describes a microcapillary-based approach that addresses these key challenges. Our approach utilizes translational stage elements and alignment end caps that are fixed in place once configured, rather than tightly fitting capillaries. This new approach enables alignment to within ±10 µm and allows greater flexibility in choosing the dimensions of the capillary, which contributes to the size and stability of formation of the double emulsion. Importantly, it also allows the user to compensate for the deviations from ideal shape that occur in pulled glass capillaries, which has been a source of failure with previous methods. A detailed description of the critical design and operational parameters that affect double emulsion generation in these capillary microfluidic devices is provided.

Highlights

The last two decades have seen great progress in the use of microfluidic technologies to miniaturize biological, chemical, and medical processes
In an effort to improve the robustness and functionality of droplet microfluidic platforms, some devices have been constructed from nested glass microcapillaries as an alternative to more conventional materials such as polydimethylsiloxane (PDMS) (Chu et al 2007; Kim et al 2007, 2013; Shah et al 2008; Utada et al 2005)
We describe a highly controllable approach to capillary microfluidic device construction, which utilizes specially designed poly(methyl methacrylate) (PMMA) end caps to achieve capillary alignment and to present precisely defined inlet ports for all source flows

Summary

Introduction

The last two decades have seen great progress in the use of microfluidic technologies to miniaturize biological, chemical, and medical processes. In an effort to improve the robustness and functionality of droplet microfluidic platforms, some devices have been constructed from nested glass microcapillaries as an alternative to more conventional materials such as polydimethylsiloxane (PDMS) (Chu et al 2007; Kim et al 2007, 2013; Shah et al 2008; Utada et al 2005) These microcapillary devices rely on coaxial alignment of the nested capillaries and can be used to generate both single and multiple emulsion droplets depending on the number and configuration of the fluid flows (Shah et al 2008). As is true of PDMS-based devices, no standardized fluidic connections exist and syringe needles are often used as improvised inlets and outlets (Kim et al 2013) These factors, together with problems with reproducibility, may have contributed to the limited use of such capillary devices in recent years

Methods

Results

Conclusion