A polyamide 6,6 (PA66) fabric pre-treated with a double barrier dielectric (DBD) atmospheric plasma in air was coated with 1 and 5 layers of an intrinsically conducting glycerol-doped PEDOT:PSS polymer (PEDOT:PSS + GLY) with the final objective of developing a cost-competitive and temperature controllable flexible-heating element to be used in clothing encapsulated between an outer and an inner separator layer in order to provide heat-reflecting properties and uniform temperature distribution, respectively. FTIR, DSC, TGA, SEM, EDS, XRD and DMA analyses show significant changes in morphology, chemistry, enthalpy, crystallinity and glass transition temperature confirming that PEDOT:PSS and glycerol are not only spread over the PA66 yarn surfaces but are dispersed in the bulk facilitating relaxation and increasing structure and chain flexibility. Electrochemical and electrical resistivity (ρ) measurements confirm that the plasma treated PA66 coated with 5 layers of PEDOT:PSS + GLY presents the highest stability, resistance and capacitive behaviour, and the best capability of storing electrical energy. This configuration needs only 7.5 V to induce a temperature change up to 38 °C at a current density of 0.3 A g⁻¹. The desired temperature is easily adjustable as a function of the applied voltage and by the number of coated layers of PEDOT:PSS + GLY. Despite the need to improve the uniformity of the coating thickness on the fabric for uniform heat generation, the observed results are quite impressive since they can be compared to the temperature obtained in carbon nanotube composites using similar voltages. This cost-competitive, safe, highly flexible and stable thermoelectric fabric has potential for use in large area textiles as a heating element in a wide range of applications such as garments, carpets, blankets and automotive seats.

A cost-effective optical sensor for continuous in-situ monitoring of turbidity and suspended particulate matter concentration (SPM), with a production cost in raw materials less than 20 €, is presented for marine or fluvial applications. The sensor uses an infrared LED and three photodetectors with three different positions related to the light source—135º, 90º and 0º—resulting in three different types of light detection: backscattering, nephelometry and transmitted light, respectively. This design allows monitoring in any type of environment, offering a wide dynamic range and accuracy for low and high turbidity or SPM values. An ultraviolet emitter–receiver pair is also used to differentiate organic and inorganic matter through the differences in absorption at different wavelengths. The optical transducers are built in a watertight structure with a radial configuration where a printed circuit board with the electronic signal coupling is assembled. An in-lab calibration of the sensor was made to establish a relation between suspended particulate matter (SPM) or the turbidity (NTU) to the photodetectors’ electrical output value in Volts. Two different sizes of seashore sand were used (180 µm and 350 µm) to evaluate the particle size susceptibility. The sensor was tested in a fluvial environment to evaluate SPM change during sediment transport caused by rain, and a real test of 22 days continuous in-situ monitoring was realized to evaluate its performance in a tidal area. The monitoring results were analysed, showing the SPM change during tidal cycles as well as the influence of the external light and biofouling problems.

Poly(vinyl alcohol) (PVA) in multifilament and braided yarns (BY) forms presents great potential for the design of numerous applications. However, such solutions fail to accomplish their requirements if the chemical and thermomechanical behaviour is not sufficiently known. Hence, a comprehensive characterisation of PVA multifilament and three BY architectures (6, 8, and 10 yarns) was performed involving the application of several techniques to evaluate the morphological, chemical, thermal, and mechanical features of those structures. Scanning electron microscopy (SEM) was used to reveal structural and morphological information. Differential thermal analysis (DTA) pointed out the glass transition temperature of PVA at 76 °C and the corresponding crystalline melting point at 210 °C. PVA BY exhibited higher tensile strength under monotonic quasi-static loading in comparison to their multifilament forms. Creep tests demonstrated that 6BY structures present the most deformable behaviour, while 8BY structures are the least deformable. Relaxation tests showed that 8BY architecture presents a more expressive variation of tensile stress, while 10BY offered the least. Dynamic mechanical analysis (DMA) revealed storage and loss moduli curves with similar transition peaks for the tested structures, except for the 10BY. Storage modulus is always four to six times higher than the loss modulus.