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Development of wearable sensors to monitor human healthiness and pathological states
High sensitivity, multiparametric, potentiometric biosensors for wearable and environment monitoring applications based on chemically stable, corrosion resistant and biocompatible materials. Nanostructured materials, constituted by ternary nitride alloys for biosensors, targeted to the detections of differential biological parameters will be developed. Multi-sensor arrays will be developed to detect a) general tissue or microenviromental conditions and specific biomarkers involved in chronic pathologies and in inflammatory processes. Taking advantage of the materials and the operative configuration of the sensors employed, wearable, transdermal and implantable biosensors will be developed.
A relevant class of electrochemical devices where the possibility of obtaining flexible electrodes is fundamental is constituted by potentiometric bio-sensors. In this class of devices, the potentiometric sensing electrode responds to chemical inputs such as a reaction or (bio)chemical binding of ions on the surface of the sensing electrode or of molecules with enzymes deposited thereon with a resulting change in the surface potential . From a practical and technological point of view, the main advantages of potentiometric biosensors are twofold: (i) they do not require an external power supply and (ii) the signal is independent of the detection area. Potentiometric sensors are used in a variety of fields, including medical diagnostics, environmental monitoring, food analysis, industrial process control and biodefense. They are conceptually robust, fast, simple to use, operate on site in real time and economical. This makes them exceptionally useful for new applications such as those for wearable sensors (see figure 1), a field where the flexibility of the sensor is an important plus, being able to integrate it into plasters, bracelets etc. in contact with the body.
The non-invasive nature of potentiometric biosensors and other significant characteristics, such as simplicity and cost-effectiveness, give rise to various possibilities of use. Potentiometer biosensors are therefore a class of devices of particular relevance for the valorization of InN/InGaN solid-state sensors on flexible surfaces. In fact, a further advantage of this type of material for the sensitive part of the sensor is the possibility of integrating into the same device, through the same transfer procedure (by varying only the thicknesses and morphology of the active material), a state reference electrode solid, thus making the technology more practical and reliable.
The sensors and sensor arrays will be based on nanostructured InN quantum dots implemented on InGaN nanocolumns, a chemically stable, corrosion-resistant and biocompatible material. Furthermore, this nanostructured material allows a super-Nernstian potentiometric response in the detection of ions and biomolecules, exceeding the theoretical thermodynamic limit by almost a factor of two.
Nanostructured InN/InGaN thin films will be created by “Plasma Assisted MBE” growth on silicon and SOI surfaces. The use of the latter allows easier detachment of the active surfaces for subsequent deposition on the flexible substrate due to the thin layer of silicon oxide a few nm below the surface of the substrate. The morphology and composition of the films will be controlled to obtain surfaces for the fabrication of sensor and reference electrodes. The electrochemical characteristics of the films produced will be determined. An upgrade of the MBE growth machine will be carried out to allow better control of the characteristics of the grown films.
The active surfaces will be removed by "wet" chemical attack exploiting a different solubility of the two materials in a suitable solvent. The possibility of combining a mechanical removal for the removal of the majority of the substrate with a chemical removal for the final section will also be tested. The fragments of the active surfaces will then be deposited on flexible conductive surfaces. The fragments will be stabilized by covering with electrolytic polymer membranes (e.g. Nafion). They will also be carried out for tests to determine the electrochemical characteristics of the electrodes.
EU PATENT: Method for the fabrication of indium-gallium nitride electrodes for electrochemical devices, n. 3430659 - 08.01.2020 Published n. 3707147 del 16.09.2020.
Publications:
An InN/InGaN Quantum Dot Electrochemical Biosensor for Clinical Diagnosis, Sensors 13 (2013) 13917
Epitaxial InN/InGaN quantum dots on Si: Cl- anion selectivity and pseudocapacitor behavior. Applied Physics Express, 9 (2016) 081004.
Pilot 2.3 Smart wearable and portable sensors to monitor human healthiness and pathological states (UNIMIB, UNIBG, ATS MI). Development of cutting-edge technologies, devices and solutions to accelerate the adoption of proximity medicine, focusing on diagnosis, monitoring and treatment of chronic and frail patients. Integration of patients’ motion/interactions and biological outputs. Innovative wearable, transdermal, implantable, and portable sensors will be developed and integrated with modular web-based platforms to elaborate data for each specific application.
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