Microfluidic devices are used for the storage and or manipulation of liquids with small volumes (mL to pL) in channels that are typically 10 -100 micron wide, the width of a human hair is around 100 micron or 0.1mm. Microfluidic devices can be used to carry out complicated sequences of chemical and biological operations. Their small size can offer a number of advantages including reduced costs of reagents and processes that can operate much faster than is the case at a larger scale. More profoundly the scale of microfluidic devices can be similar to biological or chemical entities and this can give rise to a whole range of wonderful devices and applications. Microfluidic devices can also be automated and this gives an advantage of higher reproducibility of operations.
There are many different types of microfluidic devices. We can categorise them in terms of: the materials that are used to make them – typically glass, silicon, polymer or some combination of these; how they are made; how liquids are moved in them; and the approaches that are used to detect chemical and biological entities that are contained within them.
The behaviour of liquids at the small scale can be very different to that at the large scale. In this video of a BioReactor-DiffusionMixer you can see that a blue and pink liquid is passed through the microfluidic device but the two liquids do not appear to mix. At this small scale the flow is laminar and any mixing is through diffusion. To create more obvious mixing, there is need to create turbulence within the microfluidic device. This can be done by introducing a mixing element within the microfluidic device where the fluids are folded over each other to create the mixing as is shown in this Intercept-MicroMixer.
A very interesting area of research is on the use of microfluidic devices for culturing of cells. This can lead to a whole range of interesting applications including for: drug discovery with the potential for replacement of animal testing; tissue engineering, and biologics or the production of therapeutics using biological approaches. You can find out more about how microfluidic devices are made and their applications for culturing of cells from this review paper.