Prof Mahesh Tirumkudulu from the Indian Institute of Technology in Bombay has developed a unique method to measure the viscosity of a drop of liquid based on the fluid mechanics of thin films.
A drop of liquid is spread over a substrate by contacting a blade with the drop and moving the blade across the substrate. The thickness of the film is determined by the competition between the viscous force that smears the liquid and the surface tension that resists the deformation of the interface. The length of the smear for a fixed sample volume can be used as a reliable measure of fluid viscosity (read more here).
This technique is especially suitable for detecting small changes in the viscosity of biological fluids such as blood, where sample sizes are small. It can be used as a non-specific screening tool for diseases and therapeutic interventions. Prof Tirumkudulu has investigated how to target Anaemia and Sickle-cell disease using the blood-smearing technique.
Anaemia affects nearly a quarter of the world population, mostly concentrated in low-income countries, while Sickle-cell disease (SCD), which is genetically inherited, is widely prevalent in sub-Saharan Africa and central India. Existing screening devices for these diseases are often expensive and require fully-equipped healthcare centres. Conversely, the analysis of a smeared blood sample enables a rapid, cost-effective screening assay that measures blood viscosity from a single blood drop.
Viscosity below a threshold due to low hematocrit indicates severe Anaemia, while a significant viscosity increase due to hardening of red blood cells upon blood deoxygenation signals SCD. Prof Tirumkudulu anticipates that the viscosity measurement technique could be useful in screening and monitoring various other disease conditions affecting blood viscosity, such as atherosclerosis, hypertension and diabetes.