FABRICATION AND OPTIMIZATION OF AN ORGANIC ELECTROCHEMICAL TRANSISTOR-BASED WEARABLE SENSOR FOR GLUCOSE MONITORING APPLICATIONS

Organic Electrochemical Transistors (OECTs) represent a very promising technology for biosensing applications, and flexible wearable electronics is surely a fertile field for OECTs-based devices. The purpose of this thesis project is to improve and optimize an OECT-based sensor for a flexible wearable device, able to detect the glucose level in the patient’s sweat in a non-invasive way. In fact, the glucose concentration in sweat varies depending on the health conditions of the patient, particularly for diabetic ones. OECTs are widely exploited in this sector due to the significant amplification and capability of transduction of the signal, the low operating voltages and the biocompatibility. The device was developed thanks to the collaboration between ChiLab-Materials and Microsystems Laboratory (Politecnico di Torino) in Chivasso and the Institute of Materials for Electronics and Magnetism (IMEM) of the National Research Council (CNR) in Parma. The structural basis of this device consists of a circular shape with a 16.58 mm radius and it is represented by the microfluidics, made of polydimethylsiloxane (PDMS). The PDMS layout facilitates the sweat absorption, which is captured by an adsorbent paper (Whatman Quantitative Filter Papers), whose aim consists in the transport of the liquid to the electrodes through a poly-(3,4-ethylene-dioxythiophene):poly-(styrenesulfonate) (PEDOT:PSS) channel. Such electrodes are made of 2 super-imposed layers: the gold bottom one and the silver top one. In particular, the latter results to be fundamental in order not to damage the contacts during the probe station measurements, which were performed with both silver and platinum functionalized gates. Initially, it was made the attempt to directly deposit the OECTs source and drain gold electrodes on the PDMS microfluidics. However, the gold electrodes on PDMS resulted to be cracked and irregular. Consequently, the contacts deposition was performed on a poly-oxydiphenylene-pyromellitimide (Kapton) substrate. After the design and development steps previously mentioned, measurements and characterization have been realized at the IMEM-CNR in Parma, with a specific focus on the bench top measurements at the probe station.