Abstract
In this work, we present the research carried out within the STEX (“Smart TEXtiles for monitoring muscle activity”) project, aimed at the development of wearable non-invasive sensors for real-time monitoring of muscle activity. The project's activities performed involved the design, fabrication, characterization and validation of two different sensors: (i) piezoresistive textile-based strain sensors for the detection of the breathing rate (BR) and (ii) flexible electrolyte-gated carbon nanotube field-effect transistor (EG-CNTFET)-based sensors for NH+4 detection in sweat. The piezoresistive textile-based strain sensors proved able to follow the chest movements during quiet breathing with a sensitivity of 22±2% , while a preliminary pilot study confirmed the possibility of using them to estimate the breath-by-breath BR during cycling activity. The EG-CNTFET-based NH+4 sensors showed a linear detection range for ammonium from 0.01 to 10 mM in artificial sweat, which covers the entire range of physiological concentrations of interest, with average sensitivities of 0.346 μA/decade and 96.94% coefficient of determination.