Advanced Sensors / Materials- Development of wearable sensors for clinical parameter monitoring

The convergence of global health trends, including ageing populations, the rinsing prevalence of chronic neurological and psychiatric disorders, and the growing imperative for sustainable healthcare systems, has catalysed a fundamental shift in medical practice. The vision of personalised medicine, which tailors’ therapeutic strategies to the individual patient, has moved from a theoretical ideal to an operational necessity. However, its realisation is critically hampered by a technological gap: the lack of tools for frequent, unobtrusive, and quantitative monitoring of key physiological and pharmacological parameters outside of clinical settings. Indeed, conventional diagnostic methods, reliant on centralised laboratory analysis of blood samples, provide high accuracy but are inherently incompatible with the demands of continuous, longitudinal health management. Their invasiveness, cost, and logistical complexity create a significant burden for patients and clinicians alike, often leading to suboptimal therapeutic outcomes. This persistent challenge has defined the central ambition of this doctoral thesis: to contribute to bridging this gap by advancing the frontier of wearable electrochemical sensors. These devices promise to transform episodic measurements into continuous data streams, offering a dynamic window into an individual’s health status. The journey documented in this thesis is rooted in the conviction that for such sensors to transition from promising prototypes to integral components of daily healthcare, their development must be guided by a holistic framework that transcends mere analytical performance. The REASSURED criteria, encompassing Real-time connectivity, Ease of specimen collection, Affordability, Sensitivity, Specificity, User-friendliness, Rapid and robust operation, Equipment free, and Deliverability, served as the foundational compass for this research, constantly reminding us that a sensor’s ultimate value is determined not in buffer solution, but in the complex, variable context of a patient’s life. This work is structured to reflect a logical progression from establishing the clinical and technological foundations to the integration of functional prototypes and the exploration of novel sensing paradigms.  Chapter 1 introduces the clinical context, outlining the imperative for continuous and personalised monitoring in modern healthcare. It traces the evolution from centralised laboratory analysis to Point-of-Care and, ultimately, wearable technologies, positioning electrochemical sensors as a key enabler within the Healthcare 4.0 paradigm.  Chapter 2 provides the essential material science toolkit, detailing the biocompatible substrates, fabrication techniques, and surface modification strategies that form the physical and chemical backbone of any wearable sensor. It discusses materials such as polyimide, polydimethylsiloxane (PDMS), and paper, alongside techniques including screen-printing, 3D printing, and laser induced graphene, as well as the critical role of nanomaterials and polymers in crafting the sensing interface.  Chapter 3 details the development of a Point-of-Care potentiometric sensor for monitoring lithium in bipolar disorders. It demonstrates how a graphite screenprinted electrode, modified with a bimetallic nanostructured and a lithiumselective membrane, can achieve sensitive and selective detection in synthetic sweat and saliva, offering a viable route for non-invasive therapeutic drug monitoring.  Chapter 4 addresses the need for greater biocompatibility in long-term wearables by developing a sweat-based sensor for the neurotransmitter dopamine. This work centres on an electrochemical platform constructed from the biocompatible polymer poly-L-cysteine and electrodeposited gold nanoparticles, validating its performance in undiluted artificial sweat for potential neurological health monitoring.  Chapter 5 represents a significant step towards system integration, presenting a wearable therapeutic drug monitoring platform for levodopa in Parkinson’s disease. This work combines a plasma-treated carbon sensor with a hydrophilic PDMS-based microfluidic patch for passive sweat sampling. The single-step plasma treatment serves the dual purpose of activating the sensor and sealing the microfluidic system, resulting in an integrated device capable of quantifying levodopa in a complex sweat matrix.  Chapter 6 undertakes a paradigm shift in affinity sensing by exploring the integration of fully synthetic, peptide-imprinted nanoMIPs with flexible laserinduced graphene electrodes. This “nanoMIP-on-LIG” approach aims to overcome the limitations of biological receptors, demonstrating preserved molecular recognition and enhanced signal transduction on a durable, scalable substrate suitable for next-generation wearable diagnostic.