PhD defence by Lorenza Pia Foglia

Abstract

Diabetes is a chronic condition that has no cure and diabetic patients manage their condition by monitoring their blood glucose. Currently this is done either by pricking their fingersseveral times a day, which is accurate but painful, or by wearing small sensors implanted in their skin, which is inconvenient, painful and not always accurate. A truly non-invasive, reliable glucose monitor has therefore become something of a “holy grail” in medical technology.

In this thesis, I investigated two different optical approaches: the first uses terahertz spectroscopy, a technique that is relatively new in glucose detection, and the second uses Raman spectroscopy, which to-date is the most promising and well-studied technology for this application.

Terahertz light is a type of invisible light that is very sensitive to water and to how sugar molecules disturb the motion of water, or of the water-like compartments in our skin. By shining terahertz pulses onto liquid samples that mimic human tissue, I show that it is possible to quantify clinically relevant glucose concentrations. This provides a proof-of concept
of the potential of terahertz technology in this research field. On top of that, I tested terahertz measurements on pig skin samples to develop a protocol to treat the skin so that it can be used as a realistic test platform for future non-invasive glucose studies.

The Raman spectroscopy system instead uses an infrared laser that is shone on the sample and a tiny fraction of the light come back with a shifted “color fingerprint” which reveals which molecules are present. I built a simplified instrument that only looks at the most informative wavelengths making the system smaller, faster and potentially cheaper, while still detecting glucose at and below physiological levels.

Together, these results clarify what is realistically possible with terahertz and Raman techniques and suggest concrete routes towards wearable, needle-free glucose monitoring devices and, more broadly, new optical tools for sensing important molecules in complexbiological fluids.

Supervisors

• Principal supervisor: Professor Peter Uhd Jepsen, Department of Electrical and Photonics Engineering, DTU
• Co-supervisor: Associate Professor, Simon Jappe Lange, Department of Electrical and Photonics Engineering, DTU

Evaluation Board

• Examiner: Professor Emma MacPherson, University of Warwick, UK
• Examiner: Professor Martina Havenith, Ruhr University Bochum, DE

Chairman

• Senior Researcher, Lars René Lindvold, Department of Electrical and Photonics Engineering, DTU

Master of the Ceremony

• TBA, Department of Electrical and Photonics Engineering, DTU