In this paper, a woven textile containing temperature and humidity sensors realized on flexible, plastic stripes is presented. The authors introduce two different sensors fabrication techniques: the first one consists of a conventional photolithography patterning technique; the second one, namely inkjet-printing, is here presented as an effective, lowcost alternative. In both cases, we obtain temperature and humidity sensors that can be easily integrated within a fabric by using a conventional weaving machine. All the sensors are fully characterized and the performances obtained with the two different fabrication techniques are compared and discussed, pointing out advantages and drawbacks resulting from each fabrication technique. The bending tests performed on these sensors show that they can be successfully woven without being damaged. A demonstrator, consisting of a mechanical support for the e-textile, a read-out electronic circuit, and a graphical PC interface to monitor the acquisition of humidity and temperature values, is also presented and described. This paper opens an avenue for real integration between printed electronics and traditional textile technology and materials. Printing techniques may be successfully used for the fabrication of e-textile devices, paving the way for the production of large area polymeric stripes and thus enabling new applications that, at the moment, cannot be developed with the standard lithography methods.Index Terms-E-textiles, humidity and temperature sensors, inkjet-printing, plastic and flexible substrates, wearable electronics. Manuscript

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This work presents the simultaneous fabrication of ambient relative humidity (RH) and temperature sensors arrays, inkjet-printed on flexible substrates and subsequently encapsulated at foil level. These sensors are based on planar interdigitated capacitors with an inkjet-printed sensing layer and meander-shaped resistors. Their combination allows the compensation of the RH signals variations at different temperatures. The whole fabrication of the system is carried out at foil level and involves the utilization of additive methods such as inkjet-printing and electrodeposition. Electrodeposition of the printed lines resulted in an improvement of the thermoresistors. The sensors have been characterized and their performances analyzed. The encapsulation layer does not modify the performances of the sensors in terms of sensitivity or response time. This work demonstrates the potential of inkjet-printing in the large-area fabrication of light-weight and cost-efficient gas sensors on flexible substrates.

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Conducting polyaniline-based chemiresistors on printed polymeric micro-hotplates were developed, showing sensitive and selective detection of ammonia vapor in air. The devices consist of a fully inkjet-printed silver heater and interdigitated electrodes on a polyethylene naphthalate substrate, separated by a thin dielectric film. The integrated heater allowed operation at elevated temperatures, enhancing the ammonia sensing performance. The printed sensor designs were optimized over two different generations, to improve the thermal performance through careful design of the shape and dimension of the heater element. A vapor-phase deposition polymerization technique was adapted to produce polyaniline sensing layers doped with poly(4-styrenesulfonic acid). The resulting sensor had better thermal stability and sensing performance when compared with conventional polyaniline-based sensors, and this was attributed to the polymeric dopant used in this study. Improved long-term stability of the sensors was achieved by electrodeposition of gold on the silver electrodes. Response to sub-parts-per-million concentrations of ammonia even under humid conditions was observed.