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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.

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.

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.

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.

Polymer-based CMUT microfabrication approaches allow low-cost fabrication of flexible transducers. However, they are characterized by processing limitations mainly related to the low glass transition temperature of polymers, reducing the possible choice of materials that can be used for electrodes and in-cavity passivation layers, the latter having a major impact on transducer performance and reliability. In this paper, we experimentally evaluate the electrical properties of these two materials in terms of dielectric dispersion and losses, and high electric field response with respect to state-of-the-art materials.

Polymer-based microfabrication approaches have been recently proposed as a low-cost alternative to traditional Capacitive Micromachined Ultrasonic Transducers (CMUT) fabrication methods. In most of the CMUT structures fabricated using such approaches, the electrodes passivation is achieved by a spin-coated polymer layer, with dielectric properties typically unsuitable to withstand the high in-cavity electrical fields. Moreover, typical layer thicknesses achievable by spin-coating bring to a significant increase of the effective gap height, inducing a very high collapse voltage and thus the need to use unpractically high operating voltages. In this paper, we investigate a process aimed at fabricating flexible CMUTs, potentially enabling high-performance, low-cost, curved, and ultra-miniaturized transducer configurations. In the proposed process, CMUT fabrication is carried out on an ultra-thin Polyimide substrate spun on a silicon wafer. The electrodes passivation is achieved by a thin SiO2 layer with excellent dielectric properties. A thin layer of SU-8 is used for the membrane fabrication and for sacrificial etch holes sealing. The devices are mechanically peeled-off from the wafer at the end of the process.