Pathological examination of blood requires the plasma to be separated from the red blood cells and the white blood cells.  Usually this is done by centrifugation (high speed rotation) of the blood. The disadvantage with this is that it requires a significant amount of blood and a centrifuge cannot be integrated with a microdevice for point-of-care applications. Researchers at IIT Bombay have now designed a microfluidic chip for blood separation, that can function with a very little blood. Importantly, the microfluidic chip offers almost 100% efficiency in the separation.

Usually, microfluidic chips either separate blood by force (electric, gravitational, magnetic); or rely on a passive separation by the application of the Zweifach-Fung bifurcation law. Simply put, the bifurcation law states that if a blood channel bifurcates (splits) the red blood cells will move where there is a higher flow rate. The challenge in using the bifurcation law is that if one designs larger channels, the law does not work, and if one designs smaller channels of micrometer dimensions, there are problems of clogging.

Dr. Amit Agrawal, Department of Mechanical Engineering, IIT Bombay explains that the new innovation has a channel size of around 0.1 millimetres (100 micrometers) instead of a few micrometres; yet the bifurcation law works at such large dimensions. The microfluidic chip has a T channel. When the blood is poured at one end of T channel the blood flows normally till it encounters a split; Red blood corpuscles continue along the straight channel with larger dimensions, whereas the plasma prefers to move through the perpendicular channel with smaller dimensions.  

This innovation is important due to several aspects. Firstly, since the dimensions of the channels are much larger it is easier to fabricate and manufacture. Secondly, separation efficiency is 99.7%, a respectable jump from earlier achieved efficiency levels of around 90%. Finally since the dimensions are significantly large, the chip does not encounter problems of clogging.

This innovation is not limited to the labs and already there are discussions of the innovation being commercialised. The fact that businesses are interested in this product proves that this innovation has a market and demand. There is no doubt that this innovation will improve diagnostic methods and improve health care directly. This microfluidic chip integrated with sensors will allow for a quick analysis with minimal blood and provide a real time monitoring at the site of a patient.