Non-invasive glucose sensing at millimetre wavelengths using impedance matching metamaterials

Abstract

Diabetes is a chronic disease that affects more than 300 million people worldwide. It is caused by abnormal glucose levels in the body. These levels are typically measured by piercing the fingers to collect blood, which is then placed on an electrochemical strip that, when inserted into a device it reads the glucose content in the blood. Nowadays, there is no commercially-established system that allows the monitoring of glucose levels without drawing blood, despite the need of millions of people that check their glucose levels on a daily basis. This thesis presents the progress towards developing a novel non-invasive glucose monitoring system that uses wireless transmission of millimetre waves (around 60 GHz) to detect glucose changes in the blood. The thesis also proposes an antireflection coating metamaterial film to enhance the diagnostic accuracy of the non-invasive glucose system. The work presented in this thesis combines theory, simulations and experiments to prove the possibility to detect glucose non-invasively. As a proof of concept, the idea is tested on controlled aqueous glucose solutions showing a nearly linear dependence between glucose levels and transmitted power. This idea is also tested in in-vivo pre-clinical experiments with a porcine subject and ten human subjects. For the in-vivo experimental campaigns, the device shows the ability to detect blood glucose spikes after the glucose is injected into the bloodstream. The last part of the thesis proposes the idea of using thin, micro-structured, metal-dielectric films in the propagation path of the signal to improve the sensitivity of the non-invasive glucose detection method. These films are antireflection coating metamaterials that match the impedance of the material that is placed behind them, thereby reducing the reflections and maximizing the transmission of the signal. Different metamaterial films are designed to operate in contact with acrylic, skin and skin-blood layers. Their performance is assessed by theory, simulations and experiments including in-vivo testing, demonstrating the antireflection effect.

Date of Award	1 May 2019
Original language	English
Awarding Institution	King's College London
Supervisor	Panos Kosmas (Supervisor)