A Modular and Cost-Effective Droplet Microfluidic Device for Controlled Emulsion Production

Abstract

The droplet microfluidic device has become a widely used tool in fields such as physics, chemistry, and biology, but its complexity has limited its widespread application. This report introduces a modular and cost-effective droplet microfluidic device for the controlled production of complex emulsions, including oil and aqueous single emulsions, and double emulsions with varying numbers of encapsulated droplets. The droplet sizes can be precisely controlled by easily replacing flat needles and adjusting the needle position within an axially accelerated co-flow field. This modular device not only allows for easy repair and maintenance in case of device clogging or damage but can also be readily expanded to produce complex emulsions. The low-cost and user-friendly nature of the device greatly facilitates the widespread adoption and utilization of droplet microfluidics.

Keywords: cost-effective; droplet; emulsion; microfluidics; modular.

Figure 1

A modular microfluidic device for creating single emulsions. (a) Schematic of the needle module. (b) Schematic of the assembled device; (c) high-speed video frames of droplet formation: W represents the channel size of the continuous phase supply; D represents the outlet channel size; L represents the distance between the flat needle tip and the entry to the outlet channel; (d) all components to be assembled for creating single emulsions; (e) an assembled modular microfluidic device. Both scale bars in (d,e) are 1 mm.

Figure 2

Generation of both W/O and O/W single emulsions. (a) High-speed video frames showing the droplet formation under different flow rate ratios. Color treatment applied to enhance observation. The scale bar is 400 μm. (b) Variation in sizes of both aqueous and oil droplets under different flow rate ratios.

Figure 3

Generation of droplets via different needles. (a) High-speed video frames showing the droplet formation using flat needles of varying diameters. Color treatment applied to enhance observation. The scale bar is 400 μm. (b) Comparison of droplet sizes using different needles (34 G (60 μm) and 30 G (160 μm)) under different flow rate ratios.

Figure 4

Generation of droplets at different needle positions. (a) High-speed video frames showing the droplet formation at different flat needle positions. Color treatment applied to enhance observation. The scale bar is 400 μm. (b) Comparison of droplet sizes at different needle positions under different flow rate ratios.

Figure 5

Droplet size analysis. (a) Optical micrograph of the monodisperse aqueous droplets. Green dyes are used here for enhancing observation. The scale bar is 250 μm. (b) The coefficient of variation (CV) for droplet size distribution. All CV values for different droplet sizes are lower than 5%.

Figure 6

A modular microfluidic device for creating double emulsions. (a) Schematic of the modular microfluidic device including three modules: the inner droplet module, the outer droplet module, and the connection module. (b) All components to be assembled for production of double emulsions. (c) An assembled modular microfluidic device. Both scale bars in (b,c) are 1 mm.

Figure 7

Generation of double emulsions with varying number of encapsulated droplets. (a) High-speed video frames showing the formation of double emulsion with 1, 2, and 3 encapsulated droplets. (b) Micrograph of the double emulsions. Both scale bars are 500 μm.