Millimeter-wave non-invasive monitoring of glucose in anesthetized rats

The realization of a non-invasive monitor for determining blood glucose concentrations in human subjects is a prescient driver for many new techniques spanning optical, chemical, electronic and radio sensors. Microwaves offer the possibility of simple, compact, non-invasive, and continuous measurement of glucose level in superficial tissue layers without significant heating, enzymatic reactions, or any short or long term deleterious effects on the tissue. This paper demonstrates the first real-time direct correlative measurements of the blood glucose concentration (using commercial blood test strips) and millimeter-wave (MMW) absorption during intraperitoneal injections of glucose, insulin, and saline in a live anesthetized animal. MMW transmission and reflection in the Ka band (27-40 GHz) was measured with a commercial vector network analyzer and non-invasive waveguides positioned on the ear. The data shows strong correlation between the blood glucose levels and MMW absorption during the experimentally induced hyper- and hypoglycemia.