Search Results (17)

Energy issues, including energy generation, conversion, transmission and detection, are fundamental factors in all systems. In micro- and nanosystems, dealing with these energy issues requires novel nanostructures and precise technology. However, both concept and setup are not well established yet in the microsystems, especially for those at the nanometer scale. Here, we demonstrate electromagnetic nanocoils with 100 nm diameters based on uniform and periodic InGaN nanoring arrays grown on patterned GaN surfaces using nanoscale selective area epitaxy (NSAE). We observed stronger photoluminescence from the periodic InGaN nanoring arrays compared to the non-uniform InGaN nanorings, which indicates good crystal quality of the InGaN nanostructure with the NSAE. Based on this kind of nanostructure, electromagnetic induction from the nanorings is detected through the rebound movement of high-energy electron diffraction patterns that are influenced by a modulated external magnetic field. Our results clearly show the generation of an inductive current and internal magnetic field in the nanorings. We anticipate this kind of nanostructure to be a potential key element for energy conversion, transfer and detection in nanosystems. For example, it could be used to fabricate microtransformers and micro- and nanosensors for electromagnetic signals. Full article

Precipitation strengthening represents a crucial strengthening approach in the realm of metals, with particular significance for magnesium. In this study, a complex LPSO–precipitate structure, which is constituted of the principal secondary phases in Mg rare earth (RE) alloys, namely the Long-Period Stacking Ordered (LPSO) phase and the aging precipitate, was successfully fabricated within a Mg-11Y-1Al alloy. Subsequently, an in-depth investigation was conducted regarding the interaction between dislocations and this LPSO–precipitate structure under varying temperature conditions. The findings revealed that, at room temperature (RT), the aging precipitates effectively hindered the movement of basal dislocations, and the activation of non-basal dislocations is rather difficult, resulting in the alloy’s high strength and low plasticity. When the temperature was elevated to 200 °C, although non-basal slip could be initiated, the LPSO–precipitate structure was capable of blocking both basal and non-basal slips. Consequently, the alloy still demonstrated high strength and low plasticity. As the temperature further increased to 250 °C, dislocations could cut through the aging precipitate particles, and the interior of the grains could provide partial deformation. Hence, the tensile elongation of the alloy was significantly enhanced, increasing from 4% to 12% as the temperature was elevated from 200 °C to 250 °C. These results suggest that the LPSO–precipitate structure still exerts a remarkable strengthening effect at 200 °C. When the temperature reaches 250 °C, the plasticity of the alloy is improved but its strength decreases. The research outcomes presented in this paper offer a novel perspective for the precise tailoring of mechanical properties through precipitation strengthening within Mg-RE alloys. Full article

The movement of liquid droplets on the energy gradient surface has attracted extensive attention inspired by biological features in nature, such as the periodic spindle-shaped nodes in spider silks and conical-like barbs of cacti, and the structure–property–function relationship of multifunctional gradient surfaces. In this study, a series of specific patterns are fabricated with 3D printing technology, followed by modification via the atmospheric pressure plasma treatment and liquid phase chemical deposition, resulting in enhancing the ability of water droplets of 5 μL to travel 18.47 mm on a horizontal plane and 22.75 mm against gravity at up to a 20° tilting angle. Additionally, analysis techniques have been employed, including a contact angle analyzer, ESCA, and a laser confocal microscope to evaluate the sample performance. This work could further be applied to many applications related to microfluidic devices, drug delivery and water/fog collection. Full article

Nanocomposites are materials of special interest for the development of flexible electronic, optical, and mechanical devices in applications such as transparent conductive electrodes and flexible electronic sensors. These materials take advantage of the electrical, chemical, and mechanical properties of a polymeric matrix, especially in force sensors, as well as the properties of a conductive filler such as silver nanowires (AgNWs). In this work, the fabrication of a force sensor using AgNWs synthesized via the polyol chemical technique is presented. The nanowires were deposited via drop-casting in polyvinyl alcohol (PVA) to form the active (electrode) and resistive (nanocomposite) sensor films, with both films separated by a cellulose acetate substrate. The dimensions of the resulting sensor are 35 mm × 40 mm × 0.1 mm. The sensor shows an applied force ranging from 0 to 3.92 N, with a sensitivity of 0.039 N. The sensor stand-off resistance, exceeding 50 MΩ, indicates a good ability to detect changes in applied force without an external force. Additionally, studies revealed a response time of 10 ms, stabilization of 9 s, and a degree of hysteresis of 1.9%. The voltage response of the sensor under flexion at an angle of 85° was measured, demonstrating its functionality over a prolonged period. The fabricated sensor can be used in applications that require measuring pressure on irregular surfaces or systems with limited space, such as for estimating movement in robot joints. Full article

The integration of sensors into garments has paved the way for human activity recognition (AR), enabling users to engage in extended human motion recordings. The inherent fluidity of loose clothing allows it to mirror the wearer’s movements. From a statistical standpoint, clothing captures additional valuable insights beyond rigid body motions, improving AR. This work demonstrates how fabric’s orientation, layering and width contribute to the enhanced performance of AR with clothing in periodic motion. Experiments are reported in which a scotch yoke and a KUKA robot manipulator are used to induce the periodic motion of fabric cloth at different frequencies. These reveal that clothing-attached sensors exhibit higher frequency classification accuracy among sensors with an improvement of 27% for perpendicular-oriented fabric, 18% for triple-layered fabric, and 9% for large-width fabric, exceeding that seen with rigid attached sensors. Full article

Micromachined electric field mills have received much interest for the measurement of DC fields; however, conventional designs with lateral moving shutters could have shutter lifting in the presence of strong fields, which affects their performance. This paper presents a MEMS electric field mill utilizing a vertical movement shutter to address this issue. The sensor is designed and fabricated based on a flexible PCB substrate and is released using a laser-cutting process. The movement of the shutter is driven by an electrostatic actuator. When the driving signal is a sine wave, the shutter moves in the same direction during both the positive and negative half-periods. This facilitates the application of a lock-in amplifier to synchronize with the signal at twice the frequency of the driving signal. In experimental testing, when the vertical shutter is driven at a resonance of 840 Hz, the highest sensitivity of the sensor is achieved and is measured to be 5.1 V/kVm⁻¹. The sensor also demonstrates a good linearity of 1.1% for measuring DC electric fields in the range of 1.25 kV/m to 25 kV/m. Full article

The recent impact of COVID-19, as a contagious disease, led researchers to focus on designing and fabricating personal healthcare devices and systems. With the help of wearable sensors, sensing and communication technologies, and recommendation modules, personal healthcare systems were designed for ease of use. More specifically, personal healthcare systems were designed to provide recommendations for maintaining a safe distance and avoiding contagious disease spread after the COVID-19 pandemic. The personal recommendations are analyzed based on the wearable sensor signals and their consistency in sensing. This consistency varies with human movements or other activities that hike/cease the sensor values abruptly for a short period. Therefore, a consistency-focused recommendation system (CRS) for personal healthcare (PH) was designed in this research. The hardware sensing intervals for the system are calibrated per the conventional specifications from which abrupt changes can be observed. The changes are analyzed for their saturation and fluctuations observed from neighbors within the threshold distance. The saturation and fluctuation classifications are performed using random forest learning to differentiate the above data from the previously sensed healthy data. In this process, the saturated data and consistency data provide safety recommendations for the moving user. The consistency is verified for a series of intervals for the fluctuating sensed data. This alerts the user if the threshold distance for a contagious disease is violated. The proposed system was validated using a prototype model and experimental analysis through false rates, data analysis rates, and fluctuations. Full article

The celebration of the European Year of Architectural Heritage in 1975 in Amsterdam had a great impact on architectural debate in West Berlin, which held a similar event one year later entitled A future for our past. There was a climate of great tension in the city between the precursors of the urban development plans and the social movements in the affected neighborhoods. The article discusses the extent to which a methodological change was possible, from an approach that obliterated the existing new proposals in order to readjust the role of heritage in the urban reconstruction. The idea of declaring existing urban fabric as patrimony became the central debate of this period, in which the idea of demolition and replacement became an expression of social inequality. This article comparatively analyzes the celebration of two proposals promoted by Berlin’s architectural senator Hans C. Müller in 1976: The pilot project for Block 118 in Charlottenburg and the Symposium on Urban Structure and Urban Form in Tiergarten Süd. Two innovative and methodologically distinct approaches were to establish the principles that would regulate the internationally known reconstruction of the IBA, both the Old and the New, two years later. Full article

This study proposed an extended multi–layer heat transfer model to simulate skin burns of firefighters during firefighting. The proposed model takes into account the effect of fabric movement frequencies, fabric movement amplitudes and human body movement speeds on the heat transfer between the skin and the heat source under low–level radiative exposure. The simulation performance was validated against the simulations in the published literature in terms of the heat transfer in the multi–layer fabric system, skin temperature and skin burns. The results indicated that the fabric periodic movement caused by human body movement decreased the time to skin burns and the skin temperature increased with increasing fabric movement amplitude. During firefighting, the time to 2nd degree burn was 33.3–35.2% shorter at medium human body movement speed than at low and high movement speeds. Furthermore, at low movement speeds, the time to 2nd degree burn was negatively associated with fabric movement amplitude, whereas it was delayed by 12.9–29.8% at the fabric movement amplitude of 2.5 mm at medium and high human body movement speeds. This research provides foundational knowledge for the development of a new generation of firefighters’ protective clothing (FPC) and the assessment of skin burns in firefighters. Full article

This work proposes a mono-axial piezoelectric energy harvester based on the innovative combination of magnetic plucking and indirect impacts, e.g., impacts happening on the package of the harvester. The harvester exploits a permanent magnet placed on a non-magnetic mass, free to move within a predefined bounded region located in front of a piezoelectric bimorph cantilever equipped with a magnet as the tip mass. When the harvester is subjected to a low-frequency external acceleration, the moving mass induces an abrupt deflection and release of the cantilever by means of magnetic coupling, followed by impacts of the same mass against the harvester package. The combined effect of magnetic plucking and indirect impacts induces a frequency up-conversion. A prototype has been designed, fabricated, fastened to the wrist of a person by means of a wristband, and experimentally tested for different motion levels. By setting the magnets in a repulsive configuration, after 50 s of consecutive impacts induced by shaking, an energy of 253.41 μJ has been stored: this value is seven times higher compared to the case of harvester subjected to indirect impacts only, i.e., without magnetic coupling. This confirms that the combination of magnetic plucking and indirect impacts triggers the effective scavenging of electrical energy even from low-frequency non-periodical mechanical movements, such as human motion, while preserving the reliability of piezoelectric components. Full article

The application of tribology is not just limited to mechanical components of engineering systems. As a matter of fact, the understanding of friction and wear can be applied to everyday life. One of the important fields is skin tribology, as human skin interacts with various surfaces of different materials. This paper focuses on the friction behavior of the skin when in contact with the fabric and other materials in relative motion. The excessive friction at the fabric-skin interface may lead to discomfort, blistering, chafing, and pressure ulcers especially in athletes who experience higher friction due to rapid movement for an extended period. Other than understanding the fabric properties, it is equally important to understand the structure and properties of the skin to evaluate its function and interaction with the different fabric materials. The identification of the contributing factors of skin friction can help to design suitable fabric materials. An overview of skin functions and the factors that affect the friction on the skin–textile material interface are presented in this review article. Full article

Polyvinylidene fluoride (PVDF) and AgNO₃/PVDF composite piezoelectric fibers were prepared using near-field electrospinning technology. The prepared fibers are attached to the electrode sheet and encapsulated with polydimethylsiloxane to create an energy acquisition device and further fabricated into a dynamic sensing element. The addition of AgNO₃ significantly increased the conductivity of the solution from 40.33 μS/cm to 883.59 μS/cm, which in turn made the fiber drawing condition smoother with the increase of high voltage electric field and reduced the fiber wire diameter size from 0.37 μm to 0.23 μm. The tapping test shows that the voltage signal can reach ~0.9 V at a frequency of 7 Hz, and the energy conversion efficiency is twice that of the PVDF output voltage. The addition of AgNO₃ effectively enhances the molecular bonding ability, which effectively increases the piezoelectric constants of PVDF piezoelectric fibers. When the human body is exercised for a long period of time and the body is overloaded, the biceps muscle is found to produce 8 to 16 tremors/second through five arm flexion movements. The voltage output of the flexible dynamic soft sensor is between 0.7–0.9 V and shows an orderly alternating current waveform of voltage signals. The sensor can be used to detect muscle tremors after high-intensity training and to obtain advance information about changes in the symptoms of fasciculation, allowing for more accurate diagnosis and treatment. Full article

The paper presents an original method for the template synthesis of biomimetic porous composites using polyferrophenylsiloxane (PFPS) and the skeleton of the sea urchin Strongylocentrotus intermedius as a structuring template. The study aimed to form an organosilicon base of a composite with an inverted structure relative to the original structure of the sea urchin shell with a period of structure movement of about 20 µm and ceramic composites fabrication with the silicate base with an average pore size distribution of about 10 μm obtained by the reaction of PFPS with the inorganic base of the sea urchin test under conditions of calcination at 1000 °C followed by acid etching. The composition and morphology of the obtained composites were investigated by IR, XRD, XPS, EDX, and SEM techniques and by mercury porosimetry; the parameters of the porous structures depend on the selected methods of their synthesis. The proposed method is of fundamental importance for developing methods for the chemical synthesis of new biomimetics with a unique porosity architecture based on environmentally friendly natural raw materials for a vast practical application. Full article

The strawberry blossom weevil (SBW), Anthonomus rubi, is a well-documented pest of strawberry. Recently, in strawberry fields of Trento Province (north-east Italy), new noteworthy damage on fruit linked to SBW adults was observed, combined with a prolonged adult activity until the autumn. In this new scenario, we re-investigated SBW biology, ecology, monitoring tools, and potential control methods to develop Integrated Pest Management (IPM) strategies. Several trials were conducted on strawberry in the laboratory, field and semi-natural habitats. The feeding activity of adult SBW results in small deep holes on berries at different stages, causing yield losses of up to 60%. We observed a prolonged survival of newly emerged adults (>240 days) along with their ability to sever flower buds without laying eggs inside them in the same year (one generation per year). SBW adults were present in the strawberry field year-round, with movement between crop and no crop habitats, underlying a potential role of other host/feeding plants to support its populations. Yellow sticky traps combined with synthetic attractants proved promising for both adult monitoring and mass trapping. Regarding control, adhesive tapes and mass trapping using green bucket pheromone traps gave unsatisfactory results, while the high temperatures provided by the black fabric, the periodic removal of severed buds or adults and Chlorpyrifos-methyl application constrained population build-up. The findings are important for the development of an IPM strategy. Full article

The restriction measures linked to the COVID-19 shock suddenly highlighted the vulnerability of most socioeconomic systems, including the food sector. In a context in which the limitation to the movement of people and goods has put the longer and more structured supply chains in serious difficulty, many experiences and initiatives have emerged as viable alternatives. The aim of the research was to understand if and how the Solidarity Purchasing Groups (SPG) of Rome have contributed to the resilience of the food system of the metropolitan city during the lockdown. The research was based on the results of a questionnaire administered to the SPGs of Rome during the first period of the pandemic (April–July 2020), enriched by some in-depth interviews carried out by the authors. What emerged was that, despite the limited extent in terms of products conveyed within the whole food system, the SPGs represented an important food supply channel during the lockdown period, for two main reasons: a greater flexibility and agility in moving and in handling goods and the possibility of remunerating local farms, contributing to the resilience of the local agri-food fabric. The analysis of the results confirms the strong vitality of such Food Movements in Rome and, at the same time, allows for the identification of a series of interventions that the institutions could adopt to favor the spread of a food environment more compatible with more sustainable and fairer forms of food production and distribution. Full article