Characterization of a Flexible Glucose Amperometric Sensor Obtained through Electroless Deposited Nip Electrodes
Authors: Costa Angeli Martina , Cattarinuzzi Emanuele , Gastaldi Dario , Vena Pasquale 
Published: February 2020

Diabetes mellitus is one of the most common chronic diseases in the world (8.5 % of the world population [1]) and current projections estimate an increase in prevalence over the coming years, especially in developing countries [2]. The management of diabetes mellitus requires frequent monitoring of blood glucose levels, using a small blood sample that is obtained through a finger prick. The traditional methods of self-testing are painful, invasive, and are associated a non-negligible risk of infection for the patient. Over the last years the technological development and market demand have led toward wearable non-invasive devices that offer considerable promise for continuous monitoring of a user’s health. Deformable electronics is a promising solution for wearable non-invasive glucose monitoring [3]. This new generation of glucose sensors would maintain the high sensing performance, achieved with the current technology of traditional rigid sensor, also under the demands of wear, which can impose mechanical deformation of the substrate, and be low cost. Flexible non-enzymatic (NEG) sensor is a low cost and simple solution to achieve these requirements for wearable glucose monitoring. In this work, a preliminary study on fabrication and characterization of flexible electrochemical glucose sensors is proposed. A Nickel Phosphorus (NiP) amperometric sensor on Polyethylene terephthalate (PET) substrate is proposed. A thin layer (166 nm) of NiP was deposited by electroless technique directly onto the polymer substrate (PET, 23 mm). Elemental and electrochemical analysis were carried on the deformable sensor. NiP electrode has proven to have good electrochemical behaviour, in accordance with literature. The background cyclic voltammogram in high alkaline medium showed a well-defined curve, with anodic peak at 0.54V vs Ag/AgCl. Voltammetric response at various concentrations of glucose (0.2 mM – 1 mM) was characterized. The sensor did show a good sensitivity, comparable to the literature [4]. The influence of mechanical stress (bending) on the electrochemical response and on the glucose sensing performance of the PET/NiP sensor was examined. As concerns the application envisaged for the NiP sensor demonstrator, this is expected to make contact with the human limbs on the concave side of the bent sheet. For this reason, the tests have been devised to induce compressive stresses on the sensing side of the electrode. Bending the PET/NiP electrode to small radii of curvature (up to 5mm) has no effect upon the electrochemical behaviour, but noteworthy it leads to an enhanced sensitivity.
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