The need of cheap and easy to use biosensors for rapid diagnostics is a crucial challenge in medicine: indeed, devices must offer multiple properties such as fast response, high sensitivity, reduced need of sample processing, etc. In this respect, optical biosensors remain a promising class of biodevices. Here we present an extensive investigation of the surface properties of silver-coated zinc oxide disordered nanostructures as efficient biosensing platform to detect complex organic profiles via Raman spectroscopy. In particular, we combine low temperature and large area manufacturing techniques to offer a low-cost tool for rapid detection of untreated organic samples like human blood avoiding the usage of expensive manufacturing methods to grow ordered nanostructures and providing safer materials respect the implementation of metal nanoparticles thus opening the possibility to adopt these devices also in vivo. After an accurate study using rhodamine, comparing Raman response for as deposited and lasered surfaces, different metal layers (gold vs silver) and different metal thicknesses (from 25 to 150 nm), we successfully validate the performance of the silver-coated lasered platform on untreated human blood obtaining high resolved response and identifying several organic signatures attributable to hypoxanthine, glucose and lipoprotein.

The interfacial electrical properties of deposited oxide (SiO2) onto cubic silicon carbide (3C-SiC) were investigated after different post-oxide deposition annealing (PDA) by means of metal-oxide-semiconductor (MOS) capacitors and nanoscale capacitance mapping. The deposited oxides subjected to PDA at 450 °C in either nitrogen or forming gas showed a reduction of the interface and oxide traps, as well as an improved oxide field strength compared to the thermally grown insulating layer. Spatially resolved nanoscale capacitance mapping performed onto the oxide surface revealed that the density of the electrically active stacking faults (SFs) in 3C-SiC is diminished by appropriate PDA. The results pave the way to obtain an ideal SiO2/3C-SiC system suitable for power device applications.

The paper presents a wafer-level fabrication of a capacitive micromachined ultrasonic transducer (cMUT) using a wafer bonding process and interconnection technique without through silicon vias (TSV)/through glass vias (TGV) process. Anodic bonding technique is utilized for the fabrication and bottom electrode connections are taken by etching the structural layer of Silicon and silicon dioxide. The developed approach is reliable, repeatable and suitable for integration. An element having an array of 125 circular cMUT cell is reported having center frequency of 4.4 MHz.

ZnO nanorods (NRs) play a crucial role in the manufacturing of electronic and optical devices and sensors. Using complementary techniques, we explore how their optical and conductive performances can be improved by Excimer Laser Annealing (ELA) at 75 and 100 mJ/cm. Our data show that ELA induces the melting and re-crystallization of the NRs surface, resulting into the reduction of the average crystallite size and lattice parameter of the system and suggesting a partial transition towards metallic Zn. The increase of Zn and the removal of oxygen defects at the surface are compatible with photoelectron spectroscopies (UPS and XPS) data and explain the enhancement of the UV/visible emission ratio observed in photoluminescence. The ELA also affects the in-plane electrical conductivity: the carriers mobility improves up to 4 times depending on the laser energy density. Our results demonstrate that ELA is effective in tuning the surface properties of ZnO NRs affecting the Zn concentration at the surface and removing some oxygen defects. The combination of these two effects results into the improvement of the optical and electrical responses of the systems.

In almost every activity in space, a large number of parameters need to be continuously monitored to safely control a mission. If this statement is obvious for astronauts vital parameters, it is even truer for supervising the operating status in spacecrafts, satellites as well as living and working modules. To this end, a huge amount of sensors and devices have to be deployed to dynamically configure the space equipment both autonomously and on ground. In this scenario, the weight and the rigidity of all these devices still represents the major challenge, even if the cost per kg of the payload has been considerably reduced in the last few years. Flexible sensors can provide a valuable solution to this issue, offering ultra-light and wearable devices to be used as standalone system or integrated in large networks. In this work, we review the most significant flexible sensors that can potentially represent a valuable solution for the space environment for monitoring a large variety of functions from the structural integrity of a space module to the control of the fine gesture of astronauts in extravehicular activity.

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.

We report the dielectric characterization of three commercially available, high-permittivity Rogers laminates in the sub-terahertz range, by means of terahertz time-domain spectroscopy measurements in reflection mode. A transmission-line model is developed to obtain the reflectance spectra as a function of the frequency-dispersive complex relative permittivity of the substrates. The latter is fitted through optimization to a single Lorentzian term, which is shown to accurately reproduce the measured reflectance spectra. The substrates RO3010 and RT/duroid 6010.2LM exhibit significant frequency dispersion of both their relative permittivity and loss tangent. Conversely, the thermoset microwave laminate TMM10i is characterized by both a lower frequency dispersion and overall dielectric losses, thus making it a promising candidate for the design of low-profile and broadband components for novel terahertz applications. Owing to the simple Lorentzian dispersion model used for the description of the relative permittivity, the presented results can serve as a reference, and they can be directly introduced in design and optimization workflows for novel devices in emerging terahertz applications.

The imaging x-ray polarimetry explorer (IXPE) was launched on December 9, 2021, from Cape Canaveral into a low-Earth equatorial orbit. The mission, led by NASA in collaboration with the Italian Space Agency (ASI), features three identical telescopes, each with an imaging x-ray photoelectric polarimeter at the focus of an x-ray mirror assembly. Each focal-plane detector includes a set of four calibration sources powered by a 55Fe nuclide to monitor the detector's performance. Of these sources, one produces polarized x-rays at two energies and the remaining three generate unpolarized radiation. Here we present the status of this monitoring program, starting from installation of the flight nuclides before on-ground environmental testing of the observatory through recent on-orbit measurements during science operations.

Wearable electronics is now revolutionizing the world of smart sensors offering tremendous solutions to a variety of applications that span from biomedical market to gaming and fashion sectors. In this scenario, physical sensors play a crucial role since they offer fast and reliable feedback on human motion, even for fine gestures, and can detect vital physiological parameters such as breathing and heart beating, while being able to be easily integrated into textile. Among wearable physical sensors, thermoplastic materials are utilized for their sensitivity and high stretchability. Moreover, these materials exhibit a good chemical resistance and implement low-cost manufacturing processes. In this work, we report a full characterization of a new thermoplastic nanocomposite material comparing its performances with and without preconditioning for strain up to 20%. Together with a measured gauge factor (GF) of about 10, sensors without preconditioning exhibit very good stability and they result to be a good candidate for wearable applications. We demonstrate this statement by analyzing the performance of a smart wristband prototype that integrates these strain gauges, obtaining very high performance of the sensors without prestrain in gesture recognition tasks with an accuracy and F-score of about 94%.

Background: Relationships between reflectivity, hardness and chemical composition of the dispersed phase, included in orthodontic composites Transbond XT (Trans), Light-Cure Orthodontic Paste (Leone) and Bisco Ortho Bracket Paste LC (Bisco), were investigated in vitro to evaluate whether reflectivity results can be useful in internal material composition interpretation, thus obtaining information on mechanical behaviours. Methods: Light transmission through 36 resin discs was measured with a UV/Vis spectrophotometer, evaluating the spectral range from 190-1100 nm. To have a benchmark of material hardness and internal composition, Vickers measurements and Cross-Sectional Focus Ion Beam Scanning Electron Microscopy (FIB/SEM) analysis were provided. Results: Bisco has the highest reflectivity, Leone shows an absorption pattern in the UV region similar to Bisco and Transbond has the lowest reflectivity compared to the others. This trend is confirmed by FIB/SEM imaging, showing a more similar induced roughness and internal composition for Bisco and Leone, with respect to Transbond. Higher filler presence in the composition of Bisco and Leone justifies a higher hardness of these two materials, with respect to Transbond, as confirmed by Vickers measurements. Conclusions: Bisco and Leone show similar optical responses and similarities in mechanical performance. This statement is explained by the lower and similar filler content as confirmed also by FIB/SEM analysis. The inner composition of Bisco and Leone provides a higher value of microhardness, as demonstrated by Vickers measurements. Therefore, this study confirms that the UV-Vis analysis can also offer a significant overview on the internal material composition, thus indirectly providing information on the mechanical properties of orthodontic composites.

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.

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.

In this work we present a WSN architecture for precision agriculture. The network is built on a star configuration with two protocols of connectivity: NB-IoT for the gateway and LoRa for sensor nodes. Sensor node owns solar harvesting and radio communication capabilities, low power MCU for simple edge computing, I2C and analog interface for sensors. The hardware has been designed to enable deep-sleep current <1?A. Communication protocol between nodes and the gateway has been optimized to allow synchronization of the transmission/reception window while maximizing the sleep time, contributing to further reduce the power budget of the node. We demonstrate that all these features enable battery-less operativity in specific scenarios.

BackgroundBond 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.MethodsTwelve enamel discs, from human premolars, were randomly coupled to one orthodontic adhesive system (Transbond XT (TM) 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.ResultsOrthodontic 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.ConclusionA 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.

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.

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 favored by a controllably sharp spectral response, e.g., filtering, sensing, switching, and 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.

We experimentally investigate the photothermal conversion in disordered silicon nanowires (SiNWs) grown on a glass substrate by plasma-enhanced chemical vapor deposition. The temporal and spatial response under illumination of a 532 nm laser has been measured by means of an infrared (IR) thermocamera. Fast heat generation and adjustable temperature increase from a few tens up to ?600 °C have been observed in a confined small region around the laser spot. The performing photothermal conversion is related to the efficient light trapping in SiNWs, providing enhanced absorption in the visible spectrum, and nonradiative recombination of the photogenerated carriers, typically occurring in Si. These findings combined with a lowcost, low-temperature, and large-area fabrication technology promote the disordered SiNWs as a flexible heat source well suited for applications in multiple fields including biology, precision medicine, gas detection, and nanometallurgy.

Abstract: Bacterial adhesion to the surface of orthodontic materials is an important step in the formation and proliferation of plaque bacteria, which is responsible for enamel demineralization and periodontium pathologies. With the intent of investigating if adhesive resins used for bracket bonding are prone to bacteria colonization, the surface roughness of these materials has been analyzed, combining information with a novel methodology to observe the internal structures of orthodontic composites. Scanning electron microscopy, combined with focus ion bean micromachining and stylus profilometry analyses, were performed to evaluate the compositional factors that can influence specific pivotal properties facilitating the adhesion of bacteria to the surface, such as surface roughness and robustness of three orthodontic adhesive composite resins. To confirm these findings, contact angle measurements and bacteria incubation on resin slide have been performed, evaluating similarities and differences in the final achievement. In particular, the morphological features that determine an increase in the resins surface wettability and influence the bacterial adhesion are the subject of speculation. Finally, the focused ion beam technique has been proposed as a valuable tool to combine information coming from surface roughness with specific the internal structures of the polymers.

The demand for a continuous increment of crop production reducing at the same time the impact on the used resources is a challenge that can be solved only exploiting the full potential of sensors technology applied in precise agriculture. In this review, we present the most recent advances in remote sensing technologies to be deployed in field and in greenhouses to monitor multiple key parameters such as air temperature, solar radiation, vegetative index, plant microclimate, soil feature, etc.