The determination of glucose levels in the blood is painful, costly and error prone. Various attempts have been made to provide a true non-invasive measurement of blood glucose. These include efforts that either misinterpret or mis claim non-invasive (to minimally invasive) and/or blood glucose (to interstitial glucose). When the constraints above are enforced along with the criteria of a method strongly rooted in physics, the list is greatly shortened.
A transverse electromagnetic wave (We’ll call it simply light here for ease) has a plane that the electric field oscillates within. In optics this defines the plane of polarization. Further, certain materials tend to alter the optical polarization of a light beam. Some limit the transmission of polarized light (like polarizing sunglasses or LCD screens) while other materials rotate the polarization state. This property is called optical activity and has been used as a chemical detection and quantification method as early as 1849. The glucose molecule has very high optical activity for the wavelengths we are using in a general sense – and specifically within the realm of human physiology it dominates.