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Quantum Cascade Laser Tests Blood Sugar

PRINCETON, N.J., Aug. 25, 2014 — A new laser system could eliminate the need for conventional finger-prick tests for diabetics.

A team from Princeton University has developed the new technique, which measures blood sugar by directing an IR quantum cascade laser at a person’s palm. The laser light is partially absorbed by sugar molecules in the patient’s body; the amount of absorption is used to measure the level of blood sugar.

The light’s target is not the blood, the researchers said, but dermal interstitial fluid, which has a strong correlation to blood sugar. The researchers employed mid-infrared laser light because it is harmless and largely unaffected by other chemicals in the body.


Members of the research team test the new laser system. Images courtesy of Frank Wojciechowski/Princeton University.


MIR radiation requires relatively high power and stability to penetrate the skin, making it difficult to harness with standard lasers. The quantum cascade laser produces the desired frequency, power and stability.

In the study, the researchers used the laser to measure the blood sugar levels of three healthy people before and after they each ate 20 jellybeans. Measurements were also taken with the conventional finger-prick test. These tests were repeated over several weeks.

According to the researchers, the results indicated that the laser measurement readings produced average errors that were somewhat larger than standard blood sugar monitors, but remained within the clinical requirement for accuracy. In measuring blood glucose levels, readings must be within 20 percent of the patient’s actual blood sugar level. The new system has demonstrated 84 percent accuracy.


The new monitor uses a quantum cascade laser, instead of a blood sample, to read blood sugar levels.


“We are working hard to turn engineering solutions into useful tools for people to use in their daily lives,” said Dr. Claire Gmachl, a professor of electrical engineering at Princeton. “With this work we hope to improve the lives of many diabetes sufferers who depend on frequent blood glucose monitoring.”

The new laser system originally filled up a moderate-sized workbench, they said, and also needed an elaborate cooling system to function properly. With further work, the laser now operates at room temperature. Next they plan to shrink the laser system to a portable size, which would help diabetics to check their own condition.

The work was funded by the Wendy and Eric Schmidt Foundation, the National Science Foundation, Daylight Solutions Inc. and Opto-Knowledge Systems. The research was published in Biomedical Optics Express (doi: 10.1364/boe.5.002397). 

For more information, visit www.princeton.edu.


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