Wearable multi-electrode platform for ion sensing

Field: Engineering (Physical Sciences)

With the growth of personalized medicine and e-Health, there has been an increasing interest in the development of accurate sensing systems able to support this healthcare revolution for both in- and off-hospital monitoring. Remote biosensing devices can dramatically simplify the acquisition, management and exchange of clinical data and facilitate check-ups without moving the patient and/or the physician. In addition, the emerging data-driven healthcare model enables the delivery of personalized treatments, the so-called personalized medicine. This is a recent branch of medicine that tackles the low efficacy of many pharmacological treatments as it is now well-known that the response of each individual may vary significantly from person to person. Wearable devices occupy a primary role in this data-driven revolution to collect data in medicine. Despite the great research efforts, current wearable biosensors still have several issues, such as poor collection, separate sampling and analysis, low multi-sensing capabilities, and lack of data correlating sweat and blood values. Progress in materials science to enhance sensitivity, selectivity, detection range, and reduce costs is also needed. This thesis investigates and addresses some of the challenges related to wearable chemical sensors, with particular interest on sweat sensing. This field is very attractive as this biofluid is highly promising as alternative to blood in diagnostics. In fact, it is readily accessible and reproducible, it does not require invasive procedures like blood collection, it contains several recognized biomarkers with diagnostic capabilities and good correlation with blood values, and it can be easily monitored continuously. In this thesis, a wearable electrochemical platform addressing some of these challenges is fabricated. This device enables the monitoring of several ions for different applications: Li+ for Therapeutic Drug Monitoring(TDM) of people affected by psychiatric disorders, Pb2+ for the control of heavy metal contamination, K+ and Na+ for tracking of physical exercise. The sensing is based on the use of Solid-Contact Ion-Selective Electrodes(SC-ISEs) with noble metal nanostructures. These materials are efficiently deposited in a fast on-step electrodeposition process. We demonstrate the superior behavior of our sensors in terms of sensitivity, selectivity and stability both on macro and miniaturized electrodes. The sensors are successfully proposed for the first time for the monitoring of Lithium levels in sweat for applications in TDM of psychiatric disorders. Lead sensors are also fabricated and tested in sweat to propose an innovative method for the control of heavy metal contamination. In addition, the detection of sweat Potassium and Sodium for physical exercise and hydration monitoring is also demonstrated. A custom-made flexible electrochemical sensing system including a temperature sensor, a stable reference electrode and several ion-sensing channels is fabricated by lithographic techniques. The platform is integrated with a low-cost cotton fluidics that enables the collection of fresh sweat and the disposal of the already-tested sample fluid. The successful tracking of Na+ and K+ in human volunteers during physical exercise is reported. With its high accuracy, selectivity and stability, this device represents an important step towards the development of efficient and low-cost non-invasive healthcare tracking systems for e-Health.