Graphene based wideband electromagnetic absorbing textiles at microwave bands

The design and realization of graphene based wideband electromagnetic (EM) absorbing textiles are becoming of primary interest. Hence, the development of new conductive coatings to be cast onto commercial textiles is crucial. In this article, we propose new graphene based absorbing textiles that conjugate outstanding EM absorbing properties at radiofrequency with low-weight, flexibility, cost-effectiveness, and washability. With this purpose, an innovative production process of polyvinylidene fluoride (PVDF) coatings filled with graphene nanoplatelets (GNPs) is developed for the production of radar-absorbing coated textiles, which are fully characterized in terms of morphological, electrical, and EM absorbing properties. In particular, the complex dielectric permittivity of the coated textiles including different amounts of GNPs is assessed through the measurement of the complex permittivity of a benchmark sample, the consequent estimation of the average GNP size and the prediction by simulations of the effective complex permittivity of graphene based coatings loaded with different GNP amounts. Such predicted data are crucial to design radar absorbing textiles with minimum bandwidths at −10 dB of 5 GHz and reflection coefficients below −5 dB over all the frequency range from 8 up to 18 GHz. These textiles are then produced and characterized in terms of reflection coefficient in free space against a plane wave with normal incidence. The obtained results demonstrate the full satisfaction of the design requirements. In fact, the produced samples show a reflection coefficient with a bandwidth at −10 dB up to 77% of the resonant frequency

Wearable graphene-based fabric electrodes for enhanced and long-term biosignal detection

Wearable health sensing devices are crucial and the development of multi-sensing textiles for non-invasive and continuous long-term biosignal monitoring is of primary interest. Nowadays, different wearable sensors are available but they usually lack comfort for continuous use during normal daily life activities. In this study, new graphene-based flexible dry electrodes are investigated to overcome the limitations of the currently available electrodes. Briefly, they are realized through casting PVDF (polyvinylidene fluoride)/GNP (graphene nanoplatelets) nanocomposite over commercial textiles. These electrodes are soft and flexible and adhere more easily to the skin. In terms of performance, the PVDF/GNP electrodes show lower impedance per unit area compared to commercial ones, hence they can be employed for biosignal detection. In particular, the developed electrodes are used for electrocardiogram (ECG) signal monitoring. The recorded ECG signal-to-noise ratio (SNR) reached up to 40 dB and all necessary ECG signal features and intervals are clearly distinguishable. Furthermore, the essential ECG signal intervals on each cadiac cycle show very small variations in time. Finally, the superhydrophobic property allows the electrodes to be used repeatedly after washing. As a final note, the developed dry PVDF/GNP electrodes provide reusability, biocompatibility, good skin-electrode contact, and no signs of skin irritation

Piezo-resistive properties of graphene based PVDF composite films for strain sensing

Graphene based polyvinylidene fluoride (PVDF)composite films have been produced and characterized in orderto investigate their piezo-resistive properties. To this purpose, anew production process has been developed, with the aim offabricating at low cost PVDF films filled with graphenenanoplatelets (GNPs). The produced films, having a GNPcontent of 1.5%wt and 2% wt, have been characterized frommorpholocial and chemical points of view. Moreover, theirpiezo-resistive properties have been investigated both in staticand cyclic conditions. The produced films show a stable andrepeatable response to the applied strain. A sensitivity of 15 hasbeen measured for the PVDF/GNP film filled at 1.5% wt,corresponding to an applied strain of 1.5