Generate droplets in microfluidic capillary
Introduction about droplets generation in microfluidic capillary
We describe in details what is digital microfluidic in the tutorial about microfluidic droplets and how to achieve it with a pressure controller in another Elveflow® application note (Digital microfluidics using pressure driven flow).
Fig.1: Photograph of chromatography tools
(a): a T-junction – (b): a Cross-junction
Need advice to generate droplets in capillary ?
Feel free to contact us at:
Ask me your question
(We will answer within 24 hours)
DROPLET GENERATION PACK
The droplet generation pack has been designed to fit most common droplet generation needs of researchers. Whatever you need, feel free to contact us to discuss about your exact need and if necessary we will adapt the pack and chips to your particular research application. Moreover for most common additional needs we already propose on the shelf option.
- Up to 10 000 droplets/sec
- Flow rate: from 0.1 µL/min to 5 mL/min
- Droplet size dispersion: 0.3%
- Change of droplets content : 100 ms
It is possible to make droplets with commercial tools, especially chromatography tools. Here we will focus on how to do it. One can easily make droplets using a cross or a T junction (Fig.1).
These tools are respectively the macroscopic equivalents of flow focusing and cross flowing microfluidic methods. The main difference is the needed setup time. The main drawback is the manufacturing dependence. It means that you cannot choose precisely your channels dimensions. You have to choose between the proposed dimensions (from 100 µm to 1 mm).
There is a main setup protocol. This protocol describes how to make fluid-fluid dispersion with:
A- Flow focusing method
B- Cross flowing method
The general protocol is the same; you bring two phases in a junction. One phase will be the continuous phase and the other one the dispersed phase (droplets) (Fig.2).
Fig.2: Schema of the global protocol to make droplets:
Microfluidic droplets generation at a T junction:
Microfluidic droplets moving into a capillary:
There are some details however, which differentiate the two methods.
A- Flow focusing with a cross junction (Fig.3)
1. The main channel is the channel where the droplets will flow
2. It is very important to connect the continuous phase perpendicularly to the main channel
3. The dispersed phase has to be connected to the channel in the continuity of the main channel
4. Control droplets sizes with input pressure driven flow
Fig.3: Scheme of droplets formation at a cross junction (flow focusing):
B- Cross flowing method (Fig.4)
- The main channel is the channel where the droplets will flow
- It is very important to connect the dispersed phase perpendicularly to the main channel
- The continuous phase has to be connected to the channel in the continuity of the main channel
- Control droplets size with input pressure driven flow
Fig.4: Schema of droplets’ formation at a T junction (cross flowing):
In conclusion, by connecting submillimeter tubes to submillimeter T and cross junctions, it is possible to generate droplets as in microfluidic devices. It is an easy method to manage the production of droplets. There is no simple alternative to the co-flowing method. But the two main methods used in microfluidics are easily done with chromatographic tools. As described in another Elveflow® application note (Digital microfluidics using pressure driven flow), droplets size are pre-determined by the characteristic dimensions of the tubes and junctions. There are more flexibilities on droplets size with flow focusing method (cross junction). Refer to [1,2] where the control of sizes is well described.
WORLD LEADER IN HIGH PERFORMANCE MICROFLUIDIC FLOW CONTROL
We provide the only microfluidic flow control system using Piezo technology that enables a blazing fast flow change in your microdevice.
: G. F. Christopher and S. L. Anna. Microfluidic methods for generating continuous droplet streams. Journal of Physics D: Applied Physics, 40(19): R319, (2007).
: A. R. Abate, A. Poitzsch, Y. Hwang, J. Lee, J. Czerwinska, and D. A. Weitz. Impact of inlet channel geometry on microfluidic drop formation. Phys. Rev. E, 80(2), (2009).