VCSEL-based spectroscopy for next generation non-invasive and wearable glucose monitoring

This project combines researchers from the Medical School and Physics with expertise in optoelectronics,
spectroscopy, and metabolic physiology, to develop advanced VCSEL-based spectroscopy aiming to provide a noninvasive
wearable sensor for glucose monitoring for patients with diabetes. A prototype will be demonstrated and
tested by the end of the project, which is the core technology for the devices to be integrated into watches. Based
on this platform, we aim to step into the research of wearable technologies for glucose monitoring in medical and
sports-performance settings.
Non-invasive wearable medical sensors capable of providing fast and continuous real-time monitoring of
physiological variables are in increasing demand. Such medical sensors are pivotal for the management of
numerous medical conditions, e.g., diabetes. Indeed, 4 million people in the UK have been diagnosed with
diabetes1 - about 10% with type 1, and the remainder with type 2, which is estimated to increase to 5 million in
20252. People with type 1 diabetes test their blood-sugar levels four to eight times a day, using invasive needleprick
methods, in order to manage blood sugar levels and maintain their health. A convenient and non-invasive
glucose monitor would revolutionise patient self-care for diabetes.
Continuous glucose monitor technology exists but sensors require subcutaneous injection (i.e. are invasive) and
have a lifespan of only one to two weeks. Constant replacement of these sensors makes the cost of these devices
prohibitively expensive (circa £3,000/year). If we are able to develop a non-invasive laser-based technology, this
would allow more patients to manage their condition continuously and thus reduce the burden on global
healthcare providers.
Laser-based spectroscopy has been proposed as one the most promising techniques for this purpose. However,
wearable technologies are influenced by movement, sweat, and temperature, which would significantly affect
laser accuracy in everyday use. This project aims to overcome these challenges through developing a technology
that uses swept operated VCSEL pairs that emit at two selective central wavelengths in near infrared band of 850-
1650 nm, which have strong absorption to water and glucose. The VCSEL emitting at 1650nm is challenging, this
will be achieved through the use of advanced quantum materials of digital alloy and antimonide quantum wells
based on GaSb substrate, which were developed recently3. With a specific algorithm, this technique is able to
provide stable and accurate measuring of the level of glucose in blood. Optimising the wavelengths, power, and
spot size of the lasers will be vital to ensure safety as a priority, while maintaining quality and effectiveness of the
device.
3-year plan
The PhD student will develop the laser-based spectroscopy technology and algorithms for analysis of glucose
levels in year one and two of the PhD. This technology will then be translated into human-based trials comparing
to (direct) venous blood glucose measurement and existing invasive continuous glucose monitor technology in
Year 3. The supervisory team consists of researchers in the Medical School and the Department of Physics and
provides an excellent basis upon which to help develop this technology and test in human trials.
The project is a collaboration with Cascade technologies (CAS), who specialise in spectroscopic instrumentation
for gas sensing and Feihong will provide the VCSELs with specified wavelengths. CAS will provide consultancy of
the design of the spectroscopy and test of our setup (Letter of Support enclosed).