2, University of Cagliari, Cagliari, , Italy
The development of wearable chemical sensors is receiving a great deal of attention in view of achieving active, non-invasive and continuous monitoring of physiological parameters for healthcare applications. In this scenario, Organic Electrochemical Transistors (OECTs) are emerging devices displaying peculiar features that are very appealing for the design of fully integrated wearable sensors. This contribution wants to show two strategies based on OECTs with the aim to realise high throughput wearable sensors that could be comfortably worn thanks to the suitable mechanical features of the material of choice (flexibility, light weight and stretchability).
Firstly, we describe the development of a fully textile, wearable chemical sensor based on an OECTs entirely made of the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) for biomarkers detection . The active polymer patterns are deposited into the fabric by screen printing processes, thus allowing the device to actually “disappear” into it. We demonstrate the reliability of the proposed textile OECTs as platforms for developing chemical sensors capable to detect in real-time various redox active molecules (adrenaline, dopamine and ascorbic acid). To this aim their performance was assessed in two different experimental contexts: i) ideal operation conditions (i.e. totally dipped in an electrolyte solution); ii) real-life operation conditions (i.e. by sequentially adding few drops of an electrolyte solution onto one side of the textile sensor). The OECTs response has also been recorded in artificial sweat, assessing how these sensors can be reliably used for the detection of biomarkers in body fluids.
Furthermore, inspired by OECTs technology, we propose a new approach based on an innovative material that allows operating with an only two terminals device, while maintaining the amplification provided by a transistor configuration. To this end, design and synthesis of a novel composite material based on Ag/AgCl nanoparticles (NPs) and PEDOT:PSS have been carried out to integrate the transduction features of Ag/AgCl into the semiconducting polymer. We have fabricated a wearable sensor by directly depositing Ag/AgCl NPs on a cotton yarn, previously modified with PEDOT:PSS, and assessed its performance as chloride sensor. The single-fiber textile sensor exhibits a logarithmic response to increasing Cl- concentration and its reliability was assessed by comparison with a planar sensor. Finally, no interference was observed for the Cl- determination when different chemical compounds were added to the sample at their typical concentration in human perspiration.
 I. Gualandi, M. Marzocchi, A. Achilli, D. Cavedale, A. Bonfiglio, B. Fraboni, Scientific Reports, 2016, 6, 33637.