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The aim of this paper is to characterize dielectric properties of polylactic acid, one of the most commonly used materials for 3D-printing, at microwave frequencies, specifically at X-band. The knowledge of the complex permittivity of this plastic material is important for many applications. The manufacturing process of the printed object also requires to investigate the possible material anisotropy. Moreover, using polylactic acid doped with carbon nanotubes it is possible to manufacture conductive materials that can be used to realize electronic devices and microwave components. 3D-printed samples, based on the polylactic acid filament and polylactic acid filament doped with carbon nanotubes, were designed and manufactured by fused deposition modeling along three different axes, in order to characterize the material and examine also its possible anisotropic effect at microwave frequencies. Complex permittivity results were obtained from the scattering parameter data using the transmission line method and a suitable measurement model.

The study of the interaction between electromagnetic waves and matter plays a crucial role in detecting materials under test (MUTs). Recently, radiofrequency (RF) planar resonator probes have been used to characterize MUTs by evaluating their dielectric properties. Many studies proposed these devices as biosensors, especially for dielectric measurement of living cellular suspension or even single cell. However, even though these cellular applications represent a starting point for medical diagnostic improvement, they do not consider cell interaction and adhesion. We proposed a preliminary study to design a circular patch resonator to detect adherent cell cultures in this work. Different configurations comprising a patch smaller, equal and greater than that of a standard culture Petri dish have been analyzed. The simulation results were then compared with the theoretical ones obtained applying the circular microstrip antenna’s empirical equation. Results showed that the simulation outcomes differed from the theoretical ones less than 1.5%. Finally, once the best patch diameter was identified, two other simulation sets were carried out to evaluate the antenna’s sensitivity. In the first set, we simulated the antenna response to four different volumes of culture medium (from 1.50 ml to 6.00 ml), while in the second one, we simulated the antenna response to different levels of C2C12 cell confluence in a fixed volume (1.5 ml) of culture medium. The results showed that the designed probe could discriminate between medium and C2C12 culture cells based on their permittivity change.

Electrical stimulation (ES) highly influences the cellular microenvironment, affecting cell migration, proliferation and differentiation. It also plays a crucial role in tissue engineering to improve the biomechanical properties of the constructs and regenerate the damaged tissues. However, the effects of the ES on the neuromuscular junction (NMJ) are still not fully analyzed. In this context, the development of a specialized microfluidic device combined with an ad-hoc electrical stimulation can allow a better investigation of the NMJ functionality. To this aim, we performed an analysis of the electric field distribution in a 3D neuromuscular junction microfluidic device for the design of several electrode systems. At first, we designed and modeled the 3D microfluidic device in order to promote the formation of the NMJ between neuronal cells and the muscle engineered tissue. Subsequently, with the aim of identifying the optimal electrode configuration able to properly stimulate the neurites, thus enhancing the formation of the NMJ, we performed different simulation tests of the electric field distribution, by varying the electrode type, size, position and applied voltage. Our results revealed that all the tested configurations did not induce an electric field dangerous for the cell vitality. Among these configurations, the one with cylindrical pin of 0.3 mm of radius, placed in the internal position of the neuronal chambers, allowed to obtain the highest electrical field in the zone comprising the neurites.

Monitoring spatio-temporal parameters of gait, such as Stride Length, Gait Time and Gait Speed, through inertial measurement units is a research topic of great interest in clinics. Despite the high interest in the field, the development of a high accuracy wearable solution for spatio-temporal parameters assessment in a clinical scenario, suitable for both normal and pathological gait, is still an open challenge. In this study we proposed a novel solution to estimate spatio-temporal parameters through Inertial Measurement Units and an optimized strap-down approach for drift reduction. For the accuracy evaluation three healthy subjects were enrolled. Each subject was equipped with two inertial sensors placed on feet. Subjects were asked to repeat seven walking trials, through the calibration volume of an optoelectronic system, used as a reference. As a clinical application, we used the solution to assess fatigue effects on healthy and pathological subjects considering the 6-Minute Walking Test. Results showed high accuracy in the estimation of spatio-temporal parameters for each subject. The mean relative error of the Stride Length estimation among subjects was 1.1±0.7% and 0.8±0.5% for the left and right side. The clinical application was conducted on a cohort of ten patients with Systemic Sclerosis and ten age-matched healthy adults. Statistical differences were observed between populations in the Stride Length and in the Gait Speed. Moreover, all subjects experienced fatigue effect reporting lower values of spatio-temporal parameters in the last minute, compared to the first one. The excellent results in the accuracy evaluation encourage application of this methodology in normal and in pathological gait monitoring where a low error in the estimation of spatial gait parameters is required.

Monitoring physiological parameters under stress conditions – i.e., heart rate, breath frequency or heart rate variability - through non-invasive and comfortable wearable devices was a research topic of great interest in many medical fields. In the last decade, several wearable devices and methods have been developed for stress monitoring, showing suitable performance in estimating the stress indicator. In spite of the interest in the field, the development of wearable solutions suitable for child neuropsychiatry applications was still an open challenge. In this study, we evaluate the cardiac activity in children - with and without neurodevelopmental disorders - through a novel wearable solution in order to compare the stress response in different structured activities and games. Each subject was equipped with a 3-lead electrocardiograph device and a piezoelectric respiratory sensor embedded into a thoracic belt. Subjects were asked to carry out five different activities previously chosen from a subset of specific behavioral tests (three different free-games and two structured activities). All experimental sessions were video-recorded. Results highlighted how wearable devices could help in estimating stress indicators for long-tests (over twenty-five minutes). The clinical application was conducted on a cohort of 32 children so divided: 13 with Specific Language Disorder, 15 with Autism Spectrum Disorder, and 4 control children without neurodevelopmental disorders. Statistical differences were observed between populations in the heart rate. Moreover, all subjects experienced stress effects evidenced by variation of heart rate and standard deviation, which are supported by the video analysis.

Recent studies show how air quality monitoring activities are fundamental because the environment has always played a vital role in the life-cycle of an artwork/monument, due to interaction with the materials. For this reason, we propose and present a measuring device able to detects different parameters. The device is instrumented with a microcontroller that detects signals from an inertial sensor with nine degrees of freedom, a sensor for climate parameters, four gas sensors (SO 2 , O 3 , NO, NO 2 ), a lux-meter and particles matter analyzer. The goal of this study is to realize a small-size and low-cost sensor system able to evaluate and classify the effects of different factors in an original way: through a global Risk Index. The proposed and projected system allows monitoring: (a) daily thermal variations; (b) the vibrations that occur on the structure and (c) pollutant – both reductant, oxidant and depositing agents. In this paper, the structure (hardware and software) of the environmental monitoring device is presented and expounded in detail. A Risk Analysis Algorithm is proposed and evaluated. It shows how the global degrading risk is always lower than the threshold level, even if the single compound could exceed the own threshold.

Dielectric permittivity-based measurement techniques are establishing themselves as attractive solutions for assessing moisture content of historic masonry materials. The relative simplicity of the measurement principle and the inherent adaptability to diverse operating conditions are two of the most notable features of these techniques. In spite of these specific advantages, however, there are still some aspects that hinder the widespread use of permittivity-based moisture content measurement systems, and make their standardization difficult. In particular, the density of the sample under test may affect the estimation of permittivity, thus possibly leading to inaccurate moisture content measurements. As a result, the measurement system should be re-calibrated even when the same type of material is being investigated (e.g., two samples of the same type of stone, but extracted from different quarries).To circumvent this problem and to fully exploit the potential of permittivity-based moisture content measurements, in this work, a strategy for compensating for the effect of density is addressed. In order to verify the suitability of this strategy, moisture content measurements were carried out on samples of two type of stones typical of historic masonry, namely gentile stone and red-clay brick.