Paper filter to determine viscosity of solutions

Using filter paper, scientists at the Centre for Cellular and Molecular Biology (CCMB) have developed a viscometer to measure the viscosity of fluids like blood, saliva, urine and proteins in clinical diagnostics.

Paper-based viscometers are gaining prominence in affordable diagnostics because they are not only highly accureate but also smaller samples of fluids need to be collected. Viscosity is a measurement of the thickness and stickiness of solution.

A team of six scientists including students have tested the paper viscometer on saliva, which is one of the difficult solutions to test. It is not limited to medical solutions but any kind of solution can be tested.

“It can be used for anything, for viscosity measurement of any solution and molecular weight determination. The aim was to show that this device is versatile, and can be used for several things and not just fluids,” CCMB principal scientist Dr Amit Asthana

“The amount of sample needed for measurement of viscosity of saliva is very huge. With this paper viscometer only a drop of saliva just about 20 ml is needed. Likewise for blood and urine”, Dr Asthana said.

Apart from Dr Asthana, the team comprised Anirudh Rayaprolu, Saurabh Kumar Srivastava, Ketan Anand, Lavleen Bhati and Ch Mohan Rao.

Scientists found a better co-relation co-efficient using the paper viscometer than a conventional Ostwald’s viscometer. The results could be obtained much faster than the conventional methods.

Any paper can be used to make such device but the scientists have used Whatman qualitative filter paper because it more stable. A little solution will be absorbed by the paper but it won’t deform it.

“Paper has capillaries, and a solution moves in all directions. So we created directional slope by cutting it with laser. Now the solution will move within the capillary. It will absorb some liquid, to wet the surface and keep the solution inside. It is a single tube. If you fill it from one side, pressure difference will be on both sides”, Dr Asthana said. It is first paper based viscometer to measure viscosity of Newtonian and non-Newtonian fluids and for protein-stability and molecular weight determination. The results show that the paper-based viscometer could be a potential alternative for the conventional viscometers.

This device works for Newtonian fluids which include water, glycerol, and sucrose, and non-newtonian fluids like saliva and blood.