High-Throughput Parallelized Droplet Production with a Microfluidic System

By AZoNano.com Staff Writers

Topics Covered

Introduction
System Configuration
Test Performance
Analysis
Summary
About Dolomite Microfluidics

Introduction

This article describes the performance and operating procedure of Dolomite's Telos system for the production of monodisperse water-in-oil emulsions using 35 droplet junctions in parallel. This modular ground-breaking concept combines the unrivalled size distribution control of microfluidics with production rates comparable to those achieved by conventional batch methods.

The experiment was performed with a system comprising five Telos modules, each having a seven-junction, two-reagent droplet chip. Droplet size measurements were made by imaging droplet formation at each junction using Dolomite’s image analysis software. The size measurements were repeated over a period of 48 hours to evaluate droplet size consistency.

It is possible to run the Telos system with 10 modules in parallel, each supplying a chip from common fluid inputs. Each module has independent valving, enabling control of input streams, chip replacement and inspection without interrupting droplet production. A wide range of channel geometries may be implemented, allowing the system to be customized for many different applications.

System Configuration

Five Telos Clamp Modules were used to set up the system, each supplying a 7-junction, hydrophobic Telos 2 Reagent Chip. For generating water-in-oil emulsions, hydrophobic chips were used. The carrier phase was Decane with 1% Span 80 (surfactant) and the droplet (dispersed) phase was water.

The water phase was held in two 400ml Mitos P-Pump Remote Chambers, and the oil phase was held in a 3.8l Telos Remote Chamber. A 10µm pore size PEEK Bottom-of-the-Bottle Filter was used in each remote chamber.

The 3.8l remote chamber and the two 400ml remote chambers were pressurised using a Mitos P-Pump and a Mitos P-Pump with 3-way accessories respectively, as shown in Figure 1.

Using a two-stage regulator and a pneumatic connector kit, helium was supplied from a cylinder to the P-Pumps at a pressure of 8 bar. Three flow sensors were used to measure the flow rates with a range of 1-50µl/min for the water phase and a range of 30-1000 µl/min for the oil phase.

Figure 1. System setup

Test Performance

The system was run for 48 hours and droplet size measurements taken at each junction at intervals. Pressures of 1200mbar and 200mbar for oil and water respectively were applied by the P-Pumps. Resulting flow rates were initially 1049µl/min and 101µl/min for the oil and the water inputs respectively.

Figure 2 shows the images that were captured during droplet generation for all 35 junctions.

Figure 2. Images captured during droplet generation for all 35 junctions

The initial mean diameter of the samples measured at all 35 junctions was 102.4µm with standard deviation 2.2 µm (2.2%). The range of diameters measured at this time step was 96.6 to 106.7µm with 80% of junctions producing droplets between 99.4 and 104.9µm. Size measurements over 48h are summarized below.

Another test was done to determine the maximum droplet rate achievable by the Telos system. The maximum droplet rate achieved using 5 modules without jetting occurring at any junction was 156kHz, or 4.46kHz per junction. This occurred at flow rates of 12600µl/min for the oil phase and 2400µl/min for the water phase.

Over 48h there was no overall trend observed in droplet diameter with respect to time over 48h. Mean diameter across 35 junctions varied over time between 101.7 and 103.2µm with an overall average across the 48 hours of 102.3 µm.

Minor variations are attributed to changes in room temperature since decane viscosity is significantly affected by temperature. Ambient temperature was found to vary by ± 2.5°C over a 24 hour period while oil flow rates varied correspondingly between 970 and 1237µl/min at constant pumping pressure.

Analysis

There was no overall trend observed in droplet diameter with respect to time over 48h. Mean diameter across 35 junctions varied over time between 101.7 and 103.2µm with an overall average across the 48h of 102.3µm.

Minor variations are attributed to changes in room temperature, since decane viscosity is significantly affected by temperature. Ambient temperature was found to vary by ± 2.5°C over a 24 hour period while oil flow rates varied correspondingly between 970 and 1237µl/min at constant pumping pressure. Measurement uncertainty is also a significant source of error.

Figure 3. Emulsion generated by the Telos system over 2 hours

Summary

The following points are noted from the analysis:

  • The Telos system from Dolomite is capable of producing large volumes of droplets with narrow size distribution.
  • 40l of water-in-oil emulsion can be produced in 24h using 10 Telos modules.
  • Mean droplet diameter varied between 101.7 and 103.2µm across all 35 junctions over 48 hours. This variation is most likely due to changes in ambient temperature environment.
  • The standard deviation of droplet diameter across the 35 junctions was 1.4 at best and 2.3µm at worst during the 48 hour run.

About Dolomite Microfluidics

Dolomite is a world leader in Productizing Science™ and an innovator in creating microfluidic devices and solutions. We sell the coolest microfluidic products around the world, often working with partner companies to extend the range of technology available to our customers. Productizing Science™ means creating marketable and commercially successful products from scientific discovery, and Dolomite excels in commercialising microfluidic products which exceed expectations.

We offer modular, standard microfluidic systems benefiting a wide range of applications, always adhering to the principles of having multiple functionalities, scalability, user-friendly design and a cost-effective, flexible solution for our customers.

Moreover, we offer Productizing Science™ as a service, which is a product development & manufacturing partnership creating microfluidic solutions for problems which span an extremely wide range of applications. Customers come to Dolomite with their technical challenges, and Dolomite helps solve these problems using its extensive background technology.

Dolomite also designs & manufactures a wide range of world leading standard components such as OEM products, microfluidic connectors & interfaces, chips, pumps, valves, detectors, sensors & accessories. Finally, we offer design consultancy to create customized chips or connectors and/or a prototyping service for the supply of glass, metal or polymer devices, and custom microfluidic connectors.

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

For more information on this source, please visit Dolomite Microfluidics.

Date Added: Apr 18, 2014 | Updated: Apr 24, 2014
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