Generating Monodisperse Water-in-Oil Droplets for Microfluidic Applications

By AZoNano

Table of Contents

Introduction to Monodisperse Droplet Formation
Significance of Monodispersity
Monodispersity Test Procedure
P-Pump Results
Syringe Pump Results
Conclusions
About Dolomite

Introduction to Monodisperse Droplet Formation

The formation of droplets of water-in-oil or oil-in-water has found use in a myriad of applications in science and industry. Size consistency or monodispersity is crucial to make droplet microfluidics a robust instrument for performing accurate and repeatable analyses.

Significance of Monodispersity

Various droplet application examples and corresponding requirement for monodispersity are listed in the following table:

Table 1. Monodispersity requirements for droplet applications

Droplet Application Example Requirement for Monodispersity
Emulsion production in food or cosmetics Consistent texture and performance of sample
Droplets as mini chemical reactors Known chemical make-up of droplets to achieve a reaction
Drug delivery Controlled dispersion of active ingredients
Performing biochemical assays or screens Ability to keep conditions inside droplet constant and measure the effect of a single parameter

Monodispersity Test Procedure

To compare the Mitos P-Pump pressure pump technology from Dolomite (Figure 1) and syringe pump technology, droplets were created utilizing each pump type, followed by the measurement of the droplet size distribution. A high speed video was taken to yield a data sample and processed utilizing image analysis software. The carrier liquid used was mineral oil with 1% v/v Span 80, which is a surfactant for optimizing droplet stability, while the droplet liquid was water with 10% v/v blue dye.

Figure 1. Mitos P-Pump

The experimental set-up for monodispersity test of droplets created by the Mitos P-Pump is shown in Figure 2.

Figure 2. Experimental set-up for monodispersity test of droplets generated by the Mitos P-Pump

The experimental set-up for monodispersity test of droplets created by the syringe pump is depicted in Figure 3.

Figure 3. Experimental set-up for monodispersity test of droplets generated by the syringe pump

P-Pump Results

Water-in-oil droplets generated with the Mitos P-Pump and Mitos Droplet Junction Chip – Hydrophobic are shown in Figure 4.

Figure 4. Image of water-in-oil droplets formed with the Mitos P-Pump and Mitos Droplet Junction Chip

Histogram of water droplet size distribution with oil flow rate of 8.4 µl/min and water flow rate of 1 µl/min is shown in Figure 5. Sample data acquired with Mitos P-Pump and Mitos Droplet Junction Chip – Hydrophobic and analyzed utilizing image analysis software.

Figure 5. Histogram of water droplet size distribution with water flow rate of 1 µl/min and oil flow rate of 8.4 µl/min.

Measure of distribution and corresponding values are listed in Table 2, demonstrating the variation in the size of droplets generated with Mitos P-Pump.

Table 2. Properties of droplets generated with Mitos P-Pump.

Measure of Distribution Value
Mean Droplet Diameter 99.7 μm
Standard Deviation 0.6 μm
Minimum Droplet Diameter 98.5 μm
Maximum Droplet Diameter 1Q2.2 μm
Coefficient of Variation 0.6 %

Syringe Pump Results

Water-in-oil droplets generated with the syringe pump and Mitos Droplet Junction Chip – Hydrophobic are shown in Figure 6.

Figure 6. Image of water-in-oil droplets formed with a market leading syringe pump and Mitos Droplet Junction Chip

Histogram of water droplet size distribution with oil flow rate of 10 µl/min and water flow rate of 1 µl/min is depicted in Figure 7. Sample data acquired using the syringe pump and Mitos Droplet Junction Chip – Hydrophobic and analyzed with image analysis software.

Figure 7. Histogram of water droplet size distribution with water flow rate of 1 µl/min and oil flow rate of 10 µl/min.

Measure of distribution and corresponding values are given in Table 3, showing the variation in the size of droplets generated with the syringe pump.

Table 3. Properties of droplets generated with market-leading syringe pump

Measure of Distribution Value
Mean Droplet Diameter 93.4 μm
Standard Deviation 5.1 μm
Minimum Droplet Diameter 76.8 μm
Maximum Droplet Diameter 101.2 μm
Coefficient of Variation 5.5 %

Conclusions

From the results, it is evident that the Mitos P-Pump provides a better solution for generating highly monodispersed droplets when compared to a market leading syringe pump. The coefficient of variation in the droplet diameter provided by the Mitos P-Pump is 0.6% when compared to the value of 5.5% for the syringe pump.

This clearly demonstrates the difference in flow smoothness between these two pump technologies. The Mitos P-Pump’s accurate pressure-driven pumping mechanism delivers with a smooth and constant flow, when compared to the syringe pump featuring the finest motor drives and mechanics, which have slight nonlinearities, thus causing unwanted pulsation. Hence, the Mitos P-Pump technology is suitable for microfluidic applications as it delivers optimum flow smoothness.

About Dolomite

Microfluidics, also known as “lab-on-a-chip”, enables small scale fluid control and analysis, and is an emerging technology that is changing the future of instrument design. Connecting microfluidic devices to macro-scale systems presents many challenges. To help ensure success, Dolomite provides several microfluidic solutions including chips, pumps, flow sensors and other microfluidic accessories.

In addition to the wide range of standard components, Dolomite also offers the design, development and manufacturing of bespoke solutions, including custom devices, turnkey solutions and fully automated systems.

By combining specialist glass, quartz and ceramic technologies with knowledge of high performance microfluidics, Dolomite is able to provide solutions for a broad range of industries enabling manufacturers to develop more compact, cost-effective and powerful instruments.

This information has been sourced, reviewed and adapted from materials provided by Dolomite.

For more information on this source, please visit Dolomite.

Date Added: Jun 3, 2013 | Updated: Jun 11, 2013
Comments
  1. Amer El-Hage Amer El-Hage United States says:

    Very impressive test results, but will these be different if there were for example variable obstructions (i.e. beads, cells or even particulates) in the droplet liquid flow?

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of AZoNano.com.
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