Holographic sensors for wound healing
Author(s)
Zhang, Yihan
Type
Thesis
Abstract
Chronic wounds impose severe socioeconomic burdens, underscoring the need for continuous monitoring. Continuous wound monitoring provides personalised pathophysiological information for wound management, but traditional visual checks are unable to monitor the wound-healing process continuously and are limited by subjective errors. Continual monitoring in the wound milieu via the holographic sensors can reflect the wound-healing processes. Therefore, this thesis aims to integrate flexible multiplexed holographic bandage sensors with smartphone readout and machine learning (ML) pipeline, enabling continuous and non-invasive monitoring of wound biomarkers, pH, Ca2+ ions, and glucose in wound exudates. As the initial stage, we investigate flexible holographic pH and Ca2+ ion sensing bandages. Utilising the ball-bearing-based double photopolymerisation method, we overcome the inherently narrow viewing angle tolerance of <15°, enabling wide-angle interrogation (<53°). Polyurethane and PDMS are used as flexible substrates, and both flexible pH and Ca2+ ion sensors are resilient to bending and long-term usage. The feasibility of smartphone-camera readout for point-of-care (POC) colourimetric quantification via image processing is established. While technically feasible, integrating pH, Ca2+ ion, and glucose sensors with ML-based multi-biomarker mapping reveals critical barriers to POC translation, including significant sensitivity loss and low signal-to-noise ratio (SNR) in miniaturised flexible multiplexed holographic bandage sensors, inherently narrow viewing angle range preventing simultaneous smartphone imaging, and cross-interference limiting ML accuracy. Consequently, this thesis outlines future work to resolve the abovementioned limitations and validate bandage sensors in biological models. Nevertheless, this work establishes holographic bandage sensors as a feasible platform for continuous quantitative wound monitoring, laying a clear roadmap towards personalised chronic wound management at the POC.
Version
Open Access
Date Issued
2025-06-27
Date Awarded
01/12/2025
License URL
Advisor
Yetisen, Ali
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
EP/T013567/1
Publisher Department
Department of Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)