Microfluidic devices have been used to separate a variety of target cells and particles from samples like blood, urine or cerebral spinal fluid.
One approach to this separation uses an impressive, passive microfluidic technique called deterministic lateral displacement (DLD for short). The beauty lies in its simplicity: Once you have built your array, the sorting is basically a by-product of the sample flowing through the device. Your perfectly tailored microfluidic environment can run continuously, separating your desired targets (e.g. circulating tumour cells, parasites, marker DNA, exosomes, etc.…) from anything else in your sample.
So, why is it not widely used?
Well, it is not that simple (of course!)
First of all, even the simplified „naive model“ (as Timm Krueger and I love to call it) takes a bit time to think through there:
So, basically, your sample flows through an array, that is tilted in respect to the main flow. The smaller the tilt, the more lanes your flow is divided into. The more lanes, the smaller is each lane – especially around a post of the array. Now, if your particle is significantly bigger than the lane it travels in, it gets pushed into another layer and cannot follow the flow anymore. In this picture, it gets bumped to the right (spoiler: look at the last picture of this post. There a parasite gets bumped downward, while blood cells can continue to flow along horizontally).
Plethora of parameters
Secondly, there is a number of parameters that influence the DLD performance:
BUT: Although it is complicated, it is not impossible:
If this sounds intriguing, and you wonder whether DLD is right for you, contact us!