Wearable Organic Electrochemical Biosensor for human Stress Monitoring

The applications of organic materials to electrochemical sensors are growing interest for their flexibility, ease of preparation, low cost and biocompatibility [1]. The use of a transistor architecture in the sensors allows a high gain in transconductance and opens to different possible configuration measurements [2]. Hence more and more applications for organic electrochemical transistor (OECT) have been exploited, such as detection of metabolites, ions, neurotransmitters, cells, antibodies and DNA [3].Here we applied organic material on a natural textile surface, realizing a wearable electrochemical transistor. In particular, a single cotton yarn organic electrochemical transistor, low cost, completely integrated e-textile is used as selective biosensor for the selective detection of adrenaline respect to saline content in human physiological fluids. The selective process of sensing is realized through an oxidation process at the Pt-gate electrode with formation adrenaline-quinone and then of adrenochrome. The detection of adrenaline in real human physiological fluids has been faced realizing an innovative device based on double OECTs with different gate metals (Ag and Pt), and used to detect independently saline concentration and adrenaline concentration in real human sweat in a selective way. Real-time measurements show the complete independence of adrenaline sensing respect NaCl [4] sensing and the simultaneous and independent real-time monitoring of both the concentrations. The oxidation of adrenaline has been studied with UV-Visible absorbance in different conditions: in air, in presence of working silver electrode and in presence of working platinum electrode. The results confirm that the oxidation reaction is driven by the presence of platinum electrode, which leads to a faster and direct production of adrenochrome. While with silver electrode the oxidation is completely similar to spontaneous oxidation in air. With an in-situ and non-invasive approach, the selective biosensor monitor human performances (hydration and stress), could find application in sports, health care and working safety