New Microchannel Device Measures Blood Viscosity

An innovative optical device can measure blood viscosity at the point of care, providing an early warning sign of a potential cardiovascular event.

Developed by researchers at the University of Connecticut (UConn; Storrs, USA), the whole blood rheometer measures blood viscosity by extrapolation of the time it takes blood to travel through a disposable transparent microchannel card. To perform the test, a droplet of blood is placed on the card; blood then wicks into the microchannel under capillary pressure. The microchannel card is then placed between a light source and a photodiode detector, with the velocity of the wicking blood converted into a viscosity reading that indicates elevated risk for cardiac events.

Once the test is completed, the used microchannel card is discarded and replaced with a new one. Since the device itself never comes in contact with the biological sample, practitioners don’t need to sterilize it in between patients or worry about cross-contamination. According to the researchers, current blood viscosity tests involve a mechanical rheometer, which requires large samples, takes much longer, and needs to be sterilized between tests. In addition, the travel time between the medical office and the test facility means that samples are often no longer reliable.

“We were very surprised that there is no commercial option to quickly and simply check this critical piece of information,” said George Lykotrafitis, PhD, an associate professor of mechanical engineering and co-inventor of the device. “The research shows there is a connection between blood viscosity and cardiac events, and the equipment exists to test it, but not in a practical or efficient way. We decided to try to solve the problem.”

“Our technology really is plug-and-play, but the impact is significant. With this information, doctors can suggest simple life-style changes on the spot to prevent their patients from having a stroke or heart attack,” concluded co-inventor Kostyantyn Partola, MSc, who added that they are in early discussions with physicians at UConn Health and Yale University School of Medicine (Yale; New Haven, CT, USA) to conduct clinical trials.

Blood behaves as a non-Newtonian fluid (a fluid that does not follow Newton's Law of Viscosity). In a Newtonian fluid, the relation between the shear stress and the shear rate is linear, with the constant of proportionality being the coefficient of viscosity. In a non-Newtonian fluid, the relationship between shear stress and shear rate shifts, and a constant coefficient of viscosity cannot be defined. Since the velocity of blood differs when pumping and at rest, it’s viscosity also changes. Other examples of non-Newtonian fluids include paint, ketchup, toothpaste, starch suspensions, and shampoo.

Related Links:
University of Connecticut
Yale University School of Medicine