The demand for high performance multifunctional wearable devices is more and more pushing towards the development of novel low-cost, soft and flexible sensors with high sensitivity. In the present work, we describe the fabrication process and the properties of new polydimethylsiloxane (PDMS) foams loaded with multilayer graphene nanoplatelets (MLGs) for application as high sensitive piezoresistive pressure sensors. The effective DC conductivity of the produced foams is measured as a function of MLG loading. The piezoresistive response of the MLG-PDMS foam-based sensor at different strain rates is assessed through quasi-static pressure tests. The results of the experimental investigations demonstrated that sensor loaded with 0.96 wt.% of MLGs is characterized by a highly repeatable pressure-dependent conductance after a few stabilization cycles and it is suitable for detecting compressive stresses as low as 10 kPa, with a sensitivity of 0.23 kPa−1, corresponding to an applied pressure of 70 kPa. Moreover, it is estimated that the sensor is able to detect pressure variations of ~1 Pa. Therefore, the new graphene-PDMS composite foam is a lightweight cost-effective material, suitable for sensing applications in the subtle or low and medium pressure ranges.

We evaluated the toxicity of graphite nanoplatelets (GNPs) in the model organism Caenorhabditis elegans. The GNPs resulted nontoxic by measuring longevity as well as reproductive capability end points. An imaging technique based on Fourier transform infrared spectroscopy (FT-IR) mapping was also developed to analyze the GNPs spatial distribution inside the nematodes. Conflicting reports on the in vitro antimicrobial properties of graphene-based nanomaterials prompted us to challenge the host-pathogen system C. elegans-Pseudomonas aeruginosa to assess these findings through an in vivo model.

The equivalent single-conductor model of a multiwall carbon nanotube (MWCNT) interconnect is derived analytically from the rigorous formulation of the complex multiconductor transmission-line propagation equations. The expressions of the per-unit-length (p.u.l.) equivalent quantum capacitance and kinetic inductance are obtained in closed form. A new accurate approximated expression of the equivalent p.u.l. quantum capacitance is proposed. It is demonstrated, through analytical derivations and numerical calculations, that the new expression is valid for the most of MWCNT interconnect configurations, whereas a more simplified formula, obtained on the basis of qualitative considerations, produces high approximation errors. The proposed model is solved in both the frequency and time domains. Transient analyses are performed in order to predict the attenuation and time delay of a pulse signal transmitted along an MWCNT as a function of the tube length and number of shells. Simulation results are also compared with measured data available in literature

The purpose of this paper is to investigate the use of equivalent-layer models for the analysis of carbon-fiber composite materials. In this paper, we present three different models for the electromagnetic characterization (effective material properties) of fiber composites that are commonly used in aircraft and EMC/EMI shielding materials. These three models represent various orders (or levels) of detail in the fiber composite structure and, hence, capture various physical aspects of the composite. These models can be used to efficiently calculate the reflection and transmission coefficients, as well as the shielding effectiveness, of these fiber composites. We compare results of the reflection coefficient and shielding effectiveness obtained from these effective-property models to results obtained from a full numerical solution based on the finite-element (FE) method of the actual periodic fiber composite. We show that, as expected, as more of the geometric detail of the fiber composite is captured with the different models, the upper frequency limit of validity increases.

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Graphite nanoplatelets (GNPs) are bidimensional carbon nanostructures consisting of stacks of graphene sheets, having thickness in the range from one up to a few tens of nanometers, and lateral linear dimension in the micrometer range. These nanostructures represent a good candidate to replace carbon nanotubes in composites for electromagnetic applications. This paper proposes a new model based on the Maxwell-Garnett approach to compute the effective complex permittivity of GNP-filled nanocomposites. The effect of the dimensional probabilistic distribution of the nanofiller is investigated. To this purpose, an extensive experimental characterization of the morphological and physical properties of the GNPs after synthesis is performed. The proposed model is validated by comparison with the measured effective permittivity of GNP-composites with different concentrations, and it is used for the design of radar-absorbing materials in the frequency range 1-18 GHz

A new model is proposed for the transient analysis of the electromagnetic field penetration through air-embedded conductive structures realized by thin multilayered composite panels. A magnetic field controlled formulation is developed in the frequency-domain to express the tangential components of the electric field on the external faces of the composite slab as a function of the tangential components of the magnetic field by means of the surface and transfer impedances of the thin panel coated on a perfect magnetic medium. The corresponding time-domain model is obtained by applying the inverse Fourier transform to the field quantities; an efficient piecewise linear convolution procedure is developed for the numerical calculation of the resulting convolution integrals. The model is implemented in one-dimensional (1-D) and two-dimensional (2-D) FDTD codes and applied to the analysis of different shielding configurations, both in the frequency and in the time domai

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