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Fluoride-based mouthwashes and gels are preventive measures in countering demineralization and caries but, modifying environmental acidity, can reduce the wet corrosion resistance of orthodontic alloys. To evaluate chemical stability, in vitro experiments were conducted on stainless steel and nickel–titanium wires, weighed before and after immersion in household fluorinated mouthwashes and gels, measuring weight variations and elution of metal ions from acid corrosion phenomena. Elution samples were analyzed by inductively coupled plasma mass spectrometry, detecting residual ion concentration, while surface changes were analyzed under scanning electron microscopy. Results showed stainless steel wires do not undergo significant erosion when exposed to most fluorinated mouthwashes but, at prolonged exposure, alloys elute gradually greater amounts of metals and Ni–Ti wires become more sensitive to some mouthwashes. Ions’ elution varies considerably, especially for Ni–Ti wires, if exposed to household fluorinated gels, for which significant negative values were obtained. Changes, affecting wires’ outer layer, negatively act on shiny appearance and luster, reducing corrosion resistance. Although examined orthodontic wires showed good chemical stability and low toxicity, surface corrosion from exposure to fluorinated agents was observed. Home use must be accompanied by clinician prescription and, for household dental gels, must follow manufacturers’ recommendations, ensuring prophylactic action without damaging alloys surfaces.

Silicon-based digital electronics have evolved over decades through an aggressive scaling process following Moore’s law with increasingly complex device structures. Simultaneously, large-area electronics have continued to rely on the same field-effect transistor structure with minimal evolution. This limitation has resulted in less than ideal circuit designs, with increased complexity to account for shortcomings in material properties and process control. At present, this situation is holding back the development of novel systems required for printed and flexible electronic applications beyond the Internet of Things. In this work we demonstrate the opportunity offered by the source-gated transistor’s unique properties for low-cost, highly functional large-area applications in two extremely compact circuit blocks. Polysilicon common-source amplifiers show 49 dB gain, the highest reported for a two-transistor unipolar circuit. Current mirrors fabricated in polysilicon and InGaZnO have, in addition to excellent current copying performance, the ability to control the temperature dependence (degrees of positive, neutral or negative) of output current solely by choice of relative transistor geometry, giving further flexibility to the design engineer. Application examples are proposed, including local amplification of sensor output for improved signal integrity, as well as temperature-regulated delay stages and timing circuits for homeostatic operation in future wearables. Numerous applications will benefit from these highly competitive compact circuit designs with robust performance, improved energy efficiency and tolerance to geometrical variations: sensor front-ends, temperature sensors, pixel drivers, bias analog blocks and high-gain amplifiers.

Symmetry-protected resonances can be made to couple with free space by introducing a small degree of geometric asymmetry, leading to controllably-sharp spectral response. Here, we experimentally demonstrate a broken-symmetry metasurface for the technologically important low millimeter wave spectrum. The proposed metasurface is fabricated on an ultrathin polyimide substrate, resulting in a low loss and flexible structure. Measurements inside an anechoic chamber experimentally verify the theoretically predicted sharp spectral features corresponding to quality factors of several hundreds. The demonstrated sharp response is also observed with the complementary structure which responds to the orthogonal linear polarization (Babinet's principle). The designed metasurfaces can be exploited in diverse applications favoured by a controllably-sharp spectral response, e.g., filtering, sensing, switching, nonlinear applications, in either reflection or transmission mode operation. More generally, the demonstrated fabrication process provides a generic platform for low-cost, large-scale engineering of metasurfaces with minimal substrate-induced effects., 5 pages, 4 figures

IXPE scientific payload comprises of three telescopes, each composed of a mirror and a photoelectric polarimeter based on the Gas Pixel Detector design. The three focal plane detectors, together with the unit which interfaces them to the spacecraft, are named IXPE Instrument and they will be built and calibrated in Italy; in this proceeding, we will present how IXPE Instrument will be calibrated, both on-ground and in-flight. The Instrument Calibration Equipment is being finalized at INAF-IAPS in Rome (Italy) to produce both polarized and unpolarized radiation, with a precise knowledge of direction, position, energy and polarization state of the incident beam. In flight, a set of four calibration sources based on radioactive material and mounted on a filter and calibration wheel will allow for the periodic calibration of all of the three IXPE focal plane detectors independently. A highly polarized source and an unpolarized one will be used to monitor the response to polarization; the remaining two will be used to calibrate the gain through the entire lifetime of the mission., 11 pages, 8 figures

Background In fixed orthodontics, fluoride-based mouthwashes and gels are effective preventive oral devices in counteracting demineralisations and dental caries onset but, modifying environmental acidity, they can reduce the resistance to wet corrosion of orthodontic alloys. Methods To evaluate the effective chemical stability of these products, a series of in vitro experiments were performed on thirty-two preformed rectangular orthodontic wires, (twenty-four in stainless steel and eight in nickel-titanium), cut in sections, obtaining ninety-six samples. They were weighed before and after immersion in five mouthwashes and two fluorinated dental gel, at three time-points, to measure weight variations and metal ions elution by acid corrosion phenomena. Elution samples, including control group of normal saline, were analysed by inductively coupled plasma mass spectrometry, to detect metal ions residual concentration. Results Minimal variations in loss from initial weight were recorded. Metallic ions release was quantified, at all time-points, for all wires and it was considered in correlation with alloys composition, pH and Fluor concentration of mouthwashes and gels, and time-exposition. Conclusions Acidic pH substances, like fluorinated agents and normal saline considered, cause metal ions dissolution from orthodontic wires. Dissolution depended by chemical nature of the elements, alloys composition, and Fluor concentration in mouthwashes and gels. This study helps in proposing timing and methods for the usage of fluorinated agents to guarantee the prophylactic action without damaging orthodontic alloys superficial structure.

Summary Within a project co-funded by the Italian Ministry of Foreign Affairs, the final aim of which is to develop a WSN for smart monitoring of pesticides on agricultural land, the Italian and Serbian researchers have developed a hardware section of an electronic nose for pesticides. Since there are no specialized sensors which can smell the presence or absence of pesticides in the air, the electronic nose has been designed starting from an array of commercial gas sensors developed for other environmental applications. These sensors have a great advantage as they are COTS components. A measurement bench for testing the performance of the system has also been developed. Experimental tests have been conducted and the results have demonstrated the appropriateness of the idea. A test for calibration has been designed, as well, and it will be performed in the near future.

In many activities in space, astronauts need to wear pressurized spacesuits. This equipment can protect the astronaut from the hostile external environment, but at the same time impede a series of movements causing discomfort and fatigue. To monitor these limitations in the usage of spacesuits, specific sensors need to be tailored. Among the different types of devices, wearable sensors can be a promising candidate to provide this information without adding further discomfort. The success of wearables relies on the possibility to integrate multifunctional components in the textile providing almost transparent sensing of the human body. In this scenario, physical sensors play a crucial role since they offer a fast and reliable feedback of the human motion, even for fine gestures, and can detect vital physiological parameters too. Among wearable physical sensors, thermoplastic materials are interesting for their sensitivity, softness and high stretchability. Moreover, these materials exhibit a good chemical resistant and implement low cost manufacturing processes. In this work, we report an exhaustive characterization of a new thermoplastic nanocomposite material with a gauge factor better than 100. The properties of the sensing material have been tested for increasing strain (up to 40%) and for different speed, providing also procedure to increment stability of the sensor response.

Silicon Carbide based electronics remains the most suitable choice to replace silicon in power electronics. Especially in avionics SiC devices represent a reliable solution for reducing weight and size of aircraft power switching technology. However, some issues need to be solved to unleash the full potential of this kind of electronics. The most important challenge is related to the quality of the dielectric/SiC interface and to the techniques implemented to fabricate this interface. In this work, we investigate the morphological and electrical properties of low temperature dielectric films deposited on SiC substrate by using ECR-PECVD. To this end, we fabricated capacitors with silicon dioxide layer, deposited at low temperature, studying their performance with and without surface pretreatments and considering post-annealing effects at different temperatures and times.

Background The purpose of the in vitro study is to investigate and compare the morphological features and the chemical stability in weight of two different polyurethane-based blends, Smart Track (LD30) and Exceed30 (EX30), used for orthodontic aligners manufacture before and after the oral usage. Methods Twenty orthodontic aligners were randomly selected: 10 LD30 and 10 EX30, each group was divided in two subgroups, never used and intra-orally aged. By the employment of a Stereomicroscope, a section of 5 × 5 mm was cut from the buccal surface of the incisal region of each aligner. All samples were subjected to Scanning Electron Microscopy and Ageing tests in different solutions to simulate the hostility of the oral environment. The statistical method used was t-test. Results At SEM images, LD30 appears more homogeneous in texture respect to EX30. However, after clinical usage, both materials show significant structural alterations: findings have been supported by higher magnifications at SEM, by which it is clearly to observe many superficial cracks cross through the polymer structures of LD30U, absent in never used samples. LD30U surface becomes also smoother due to the disappearance of most of the conglomerates, but at the same time also rougher while EX30U shows a greater irregularity and porosity in which large and deep cracks are also highlighted. Although these changes occur persistently, in the aging tests no significant weight loss from both materials has been found, confirming the initial hypothesis of a good chemical stability and safety of both polyurethane mixtures even in conditions of severe hostility. Conclusion LD30 is the expression of the technological evolution of EX30, this is made evident above all by its morphological architecture, more homogeneous and defined but also by the chemical stability that can be appreciated even in evident critic situations.

Background Bond strength of orthodontic composite is strongly influenced by molecular and structural mechanisms. Aim of this in vitro study was to compare bond strength of light-cure orthodontic composites by measuring debonding forces and evaluating locations of bond failure. Investigations on chemical compositions clarified adhesive behaviors and abilities, exploring effects of ageing processes in this junction materials. Methods Twelve enamel discs, from human premolars, were randomly coupled to one orthodontic adhesive system (Transbond XT™ 3 M UNITEK, USA, Light-Cure Orthodontic Paste, LEONE, Italy and Bisco Ortho Bracket Paste LC, BISCO, Illinois) and underwent to Shear Bond Strength test. Metallic brackets were bonded to twenty-seven human premolar, with one of the adhesive systems, to quantify, at FE-SEM magnifications, after debonding, the residual material on enamel and bracket base surfaces. Raman Spectroscopy analysis was performed on eight discs of each composites to investigate on chemical compositions, before and after accelerated aging procedures in human saliva and sugary drink. Results Orthodontic adhesive systems showed similar strength of adhesion to enamel. The breakage of adhesive-adherent bond occurs in TXT at enamel-adhesive interface while in Bisco and Leone at adhesive-bracket interface. Accelerated in vitro aging demonstrated good physical–chemical stability for all composites, Bisco only, was weakly contaminated with respect to the other materials. Conclusion A similar, clinically adequate and acceptable bond strength to enamel for debonding maneuvers was recorded in all orthodontic adhesive systems under examination. No significant chemical alterations are recorded, even in highly critical situations, not altering the initial mechanical properties of materials.

Bacterial adhesion to the surface of the adhesive material is an important step in the formation of plaque and enamel demineralization. In order to correlate the material composition to the specific surface roughness of the resin and to the probable more favourable adhesion of bacteria, scanning electron microscopy, combined with focus ion bean micromachining, together with stylus profilometry analysis have been in vitro performed to reveal the structural nature of three orthodontic adhesive resins used for bracket bonding and, above all, to understand how compositional factors can influence specific pivotal properties such as material’s surface roughness and robustness. In particular, we speculated about the morphological features that determine an increase in the bacterial adhesion and we proposed focused ion beam technique as a valuable tool to compare the internal structures of the polymers and to determine the peculiar mechanical properties of the examined adhesive resins.

Capacitive micromachined ultrasonic transducers (CMUTs) represent a class of ultrasonic devices widely investigated for several applications such as medical imaging and non-destructive material inspections. Although many improvements, the possibility to successfully operate on nonplanar surfaces still remains challenging. In this respect, flexible electronics can represent a unique ally to enable the manufacturing ultra-thin highly conformable CMUTs. In this paper, we demonstrate a fully flexible fabrication process for a PI based CMUT device and a preliminary characterization. This flexible CMUT technology was conceived to achieve a final device composed of only two materials, i.e., Titanium for the electrodes and PI for the membrane and the backplate. The CMUT cavities were realized by Aluminium sacrificial release. We fabricated flexible CMUT test devices consisting of 7 membranes 50µm in diameter laying onto an 8µm-thick backplate. This configuration can allow the bending of the devices on very small curvature radii (down to 1 mm).

In avionics, safety is a crucial aspect and nondestructive testing (NDT) is a mandatory inspecting procedure to ensure the quality of materials before and during the lifetime of the aircraft, evaluating both the status of the materials and the degradation of the different parts of an aircraft. Especially in recent composites like Carbon Fibre Reinforce Plastics the presence of defects or the disbonds caused from accidental impacts can be very dangerous for the integrity of the wings, fuselage, etc. Among the different methods implemented in non-destructive testing, ultrasonic testing is the most common sub-surface technique to detect defects in welds, fittings, joints, bolts and adhesive bond quality. Capacitive Micromachined Ultrasonic Transducers (CMUTs) can be utilized to this end, thus permitting portable and potentially low-cost inspection. In this work, we present the fabrication and characterization of flexible CMUTs, and we discuss their potential use in NDT probes to be embedded directly on the aircraft to allow continuous and real-time monitoring of the different parts of an aircraft.

Research over the past four decades has highlighted the importance of certain brain cells, called glial cells, and has moved the neurocentric vision of structure, function, and pathology of the nervous system toward a more holistic perspective. In this view, the demand for technologies that are able to target and both selectively monitor and control glial cells is emerging as a challenge across neuroscience, engineering, chemistry, and material science. Frequently neglected or marginally considered as a barrier to be overcome between neural implants and neuronal targets, glial cells, and in particular astrocytes, are increasingly considered as active players in determining the outcomes of device implantation. This review provides a concise overview not only of the previously established but also of the emerging physiological and pathological roles of astrocytes. It also critically discusses the most recent advances in biomaterial interfaces and devices that interact with glial cells and thus have enabled scientists to reach unprecedented insights into the role of astroglial cells in brain function and dysfunction. This work proposes glial interfaces and glial engineering as multidisciplinary fields that have the potential to enable significant advancement of knowledge surrounding cognitive function and acute and chronic neuropathologies.

Glycated albumin (GA) is rapidly emerging as a robust biomarker for screening and monitoring of diabetes. To facilitate its rapid, point-of-care measurements, a label-free surface-enhanced Raman spectroscopy (SERS) sensing platform is reported that leverages the specificity of molecular vibrations and signal amplification on silver-coated silicon nanowires (Ag/SiNWs) for highly sensitive and reproducible quantification of GA. The simulations and experimental measurements demonstrate that the disordered orientation of the nanowires coupled with the wicking of the analyte molecules during the process of solvent evaporation facilitates molecular trapping at the generated plasmonic hotspots. Highly sensitive detection of glycated albumin is shown with the ability to visually detect spectral features at as low as 500 × 10-9 m, significantly below the physiological range of GA in body fluids. Combined with chemometric regression models, the spectral data recorded on the Ag/SiNWs also allow accurate prediction of glycated concentration in mixtures of glycated and non-glycated albumin in proportions that reflect those in the bloodstream.

Long-term space exploration requires an affordable and continuous provision of food and nutrients that need to be palatable so as not to upset the psycho-physical balance of the crewmembers. Moreover, a proper diet composed of fresh food enriched with key nutrients such as minerals and vitamins can minimize the detrimental effects due to microgravity in terms of bones weakening; in addition, the absence of direct incident light from the sun due to a safety shielding from cosmic rays can cause a significant reduction of vitamin D production in the skin. Smart greenhouses based on aeroponics or hydroponics technologies can represent a valuable solution to genuine food supply. Nevertheless, these structures require an affordable monitoring system able to detect key parameters such as nutrients concentration in the mist, gaseous products/pollutants together with relative humidity and temperature. Flexible, light and low-cost gas sensors based on laser-annealed zinc oxide nanostructures can be implemented for this specific application, using different morphologies within the same material for discriminating the different gases. Unluckily, this active material generally exhibits memory effects and significant drift. In this work, we propose a simple method to dramatically increase the reliability of nanostructured ZnO sensor response to be used at low working temperature (room temperature). The resulting devices exploit the porosity of disordered nanostructures thus monitoring CO, CO2, NOX and other gases present in the greenhouse.

Silicon nanowires (SiNWs) are attractive functional nanomaterials for biomedical applications. The ability to easily tune their size and density, potential biocompatibility, and knowledge of the chemical activation of SiNWs surface make them natural tools to interact with biological materials. We evaluated the possibility of exploiting SiNWs as carriers to introduce organic compounds into cells. The cellular toxicity and the internalization capacity of free-standing and label-free SiNWs were tested on Buffalo Green Monkey cells (BGM). Confocal fluorescent observation of SiNWs conjugated with fluorescein-polyethylene imine (PEI) confirmed the internalization of the NWs into the Buffalo Green Monkey Cells (BGM).

The NASA/ASI Imaging X-ray Polarimetry Explorer, which will be launched in 2021, will be the first instrument to perform spatially resolved X-ray polarimetry on several astronomical sources in the 2-8 keV energy band. These measurements are made possible owing to the use of a gas pixel detector (GPD) at the focus of three X-ray telescopes. The GPD allows simultaneous measurements of the interaction point, energy, arrival time, and polarization angle of detected X-ray photons. The increase in sensitivity, achieved 40 years ago, for imaging and spectroscopy with the Einstein satellite will thus be extended to X-ray polarimetry for the first time. The characteristics of gas multiplication detectors are subject to changes over time. Because the GPD is a novel instrument, it is particularly important to verify its performance and stability during its mission lifetime. For this purpose, the spacecraft hosts a filter and calibration set (FCS), which includes both polarized and unpolarized calibration sources for performing in-flight calibration of the instruments. In this study, we present the design of the flight models of the FCS and the first measurements obtained using silicon drift detectors and CCD cameras, as well as those obtained in thermal vacuum with the flight units of the GPD. We show that the calibration sources successfully assess and verify the functionality of the GPD and validate its scientific results in orbit; this improves our knowledge of the behavior of these detectors in X-ray polarimetry., Comment: 22 pages, 16 figures, published on Journal of Astronomical Telescopes, Instruments, and Systems