For years, research has been conducted on the use of lasers to measure blood glucose levels in diabetic patients instead of painful pricks in the finger. Japanese scientists from Tohoku University have developed their own original technique based on the use of infrared light.
Prior to these, non-invasive glucose monitoring methods used low to medium intensity infrared light. By relying on the property of glucose in the blood to "absorb" light of certain wavelengths and by measuring the amount of absorbed light, it becomes possible to determine the glucose level.
After analyzing this method, Japanese scientists came to the conclusion that it is very inaccurate, since in addition to glucose, water, protein and hemoglobin are involved in the absorption of light. To solve this problem, they decided to use more intense infrared light with a wavelength of 10 microns, which is better absorbed by glucose.
To implement their method, the researchers used flexible hollow optical fibers with small prisms at the end as light sources. In this case, the scanning was carried out not on the finger, where there is a rather thick layer of subcutaneous fat, but in the oral cavity on the mucous membrane of the lips, which is much thinner.
As a result, glucose measurements had an error of no more than 20%, which is accurate enough for clinical use.