Search Results (2,635)

In the growing field of personalized medicine, non-invasive wearable devices and sensors are valuable diagnostic tools for the real-time monitoring of physiological and biokinetic signals. Among all the possible multiple (bio)-entities, pH is important in defining health-related biological information, since its variations or alterations can be considered the cause or the effect of disease and disfunction within a biological system. In this work, an innovative (bio)-electrochemical flexible pH sensor was proposed by realizing three electrodes (working, reference, and counter) directly on a polyimide (Kapton) sheet through the implementation of CO₂ laser writing, which locally converts the polymeric sheet into a laser-induced graphene material (LIG electrodes), preserving inherent mechanical flexibility of Kapton. A uniform distribution of nanostructured PEDOT:PSS was deposited via ultrasonic spray coating onto an LIG working electrode as the active material for pH sensing. With a pH-sensitive PEDOT coating, this flexible sensor showed good sensitivity defined through a linear Nernstian slope of (75.6 ± 9.1) mV/pH, across a pH range from 1 to 7. We demonstrated the capability to use this flexible pH sensor during dynamic experiments, and thus concluded that this device was suitable to guarantee an immediate response and good repeatability by measuring the same OCP values in correspondence with the same pH applied. Full article

With the increasing need to tackle climate change, energy efficiency and reduced CO₂ emissions are proving to be one of society’s greatest challenges. Special consideration should be given to heating systems as they are prone to inefficiency due to non-optimal controller configurations and the shortage of experts or qualified technicians to optimize the operating behavior. Especially for residential heating systems, more often than not, the target metric is the achievement of specific heating and hot water temperatures by manual adjustments with limited sensor information and with little regard to efficiency. This presents potential for computer-aided optimization based on artificial intelligence techniques. In this paper, we presented a Decision Integration System that is interfaced with a data acquisition infrastructure and allows for the analysis of measured heating system data, the generation of recommended measures for efficiency improvement, and the simulative validation of recommended controller parameter changes. We presented different parts of the Decision Integration System, the interfaced data acquisition infrastructure, as well as the non-invasive sensor appliances used. We analyzed the measured data of real heating systems and evaluated our approach by generating the recommended measures based on rules created by heating system experts, which were then partially applied to the physical heating systems and partially evaluated in simulation. Finally, we compared long-term energy consumption data against the latest monitoring period after implementing the measures. Our results showed an average reduction in energy consumption of 24.52% across all considered buildings, corresponding to an approximate reduction of 8.12 tons of CO₂ emissions. Full article

Chemical nanosensors based on nanoparticles of tin dioxide and graphene-decorated tin dioxide were developed and characterized to detect low NO₂ concentrations. Sensitive layers were prepared by the drop casting method. SEM/EDX analyses have been used to investigate the surface morphology and the elemental composition of the sensors. Photoactivation of the sensors allowed for detecting ultra-low NO₂ concentrations (100 ppb) at room temperature. The sensors showed very good sensitivity and selectivity to NO₂ with low cross-responses to the other pollutant gases tested (CO and CH₄). The effect of humidity and the presence of graphene on sensor response were studied. Comparative studies revealed that graphene incorporation improved sensor performance. Detections in complex atmosphere (CO + NO₂ or CH₄ + NO₂, in humid air) confirmed the high selectivity of the graphene sensor in near-real conditions. Thus, the responses were of 600%, 657% and 540% to NO₂ (0.5 ppm), NO₂ (0.5 ppm) + CO (5 ppm) and NO₂ (0.5 ppm) + CH₄ (10 ppm), respectively. In addition, the detection mechanisms were discussed and the possible redox equations that can change the sensor conductance were also considered. Full article

This work introduces an ultraviolet (UV)-curable elastomer through the co-polymerization of aliphatic polyurethane acrylate and hydroxypropyl acrylate via UV irradiation. The UV-curable elastomer presents superior mechanical properties (elongation at a break of 2992%) and high transparency (94.8% at 550 nm in the visible light region). A robust hydrogel–elastomer stretchable sensor is fabricated by coating an ionic hydrogel on the surface of an elastomer, which enables real-time monitoring of human motion. In addition, the UV-curable elastomer can be used for 3D printing, as demonstrated by complex lattice structures using a digital light processing 3D printer. Full article

This paper presents a comprehensive holistic methodology implemented for sustainable lighting systems in educational institutions. The proposed methodology is aligned with the Sustainable Development Goals (SDGs), particularly with SDG 7 (Affordable and Clean Energy) and SDG 13 (Climate Action), and it follows international standards. The six-step process includes viability analysis, project design simulation using DIALux 4.13 software, the installation of LED lighting systems, and the redesign of some electrical circuits, followed by an analysis of return on investment and the monitorization of CO₂ and energy consumption. The proposed methodology results in significant return on investment (ROI), primarily achieved through energy savings and reduced maintenance costs. The implementation of LED tubes, combined with occupancy and natural light sensors, leads to a 66% reduction in energy consumption and a reduction of 15.63 tons (metric tons) of CO₂ annually, translating into a quick payback period of approximately 2.36 years. Additionally, the system includes Long-Term Monitoring, which ensures that energy consumption and lighting levels are continuously tracked. Full article

Manganese dioxide (MnO₂) has drawn attention as a sensitiser to be incorporated in graphene-based chemoresistive sensors thanks to its promising properties. In this regard, a rGO@MnO₂ sensing material was prepared and deposited on two different substrates (silicon and Kapton). The effect of the substrate nature on the morphology and sensing behaviour of the rGO@MnO₂ material was thoroughly analysed and reported. These sensors were exposed to different dilutions of NO₂ ranging from 200 ppb to 1000 ppb under dry and humid conditions (25% RH and 70% RH) at room temperature. rGO@MnO₂ deposited on Kapton showed the highest response of 6.6% towards 1 ppm of NO₂ under dry conditions at RT. Other gases or vapours such as NH₃, CO, ethanol, H₂ and benzene were also tested. FESEM, HRTEM, Raman, XRD and ATR-IR were used to characterise the prepared sensors. The experimental results showed that the incorporation of nanosized MnO₂ in the rGO material enhanced its response towards NO₂. Moreover, this material also showed very good responses toward NH₃ both under dry and humid conditions, with the rGO@MnO₂ sensor on silicon showing the highest response of 18.5% towards 50 ppm of NH₃ under 50% RH at RT. Finally, the synthetised layers showed no cross-responsiveness towards other toxic gases. Full article

Piezoelectric materials can realize the mutual conversion of mechanical energy and electric energy, so they have excellent application prospects in the fields of sensors, energy collectors and biological materials. The poly(vinylidene fluoride) (PVDF)-based polymers have the best piezoelectric properties in the piezoelectric polymer, but they still have a large room for improvement compared with the piezoelectric ceramics. Improving their content of the polar β phase has become a consensus to polish up the piezoelectric performance. Most available studies construct hydrogen bonds or coulomb interactions between the surface of the dopant and molecular chains by doping, which promotes the molecular chains arrangement and thus facilitates the formation of the polar β phase. Recent studies show that the ordered arrangement of molecular chains is also important for piezoelectric properties. At present, the main way to improve the piezoelectric performance of PVDF is through doping or complex heat treatment process. Here, the poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) film was treated by directional heat treatment which used a heating table. Compared with uniform heat treatment like muffle furnace heat treatment, this simple vertical temperature gradient has many advantages for the content of the β phase and the crystallinity of P(VDF-TrFE). The results of the experiment showed that the content of the β phase of films remained at about 88%. When the film thickness was limited to 100 μm and the heat treatment temperature was limited to 200 °C, its crystallinity could reach 75% and the highest piezoelectric coefficient could reach 33.5 ± 0.7 pC/N. P(VDF-TrFE) films based on the experimental methods described above that show great potential for future applications in electronic devices and biomedical applications. Full article

This paper presents the design and development of a proof of concept (PoC) open-source data logger system for wireless data acquisition via Wi-Fi aimed at bench testing and fault detection in combustion and electric engines. The system integrates multiple sensors, including accelerometers, microphones, thermocouples, and gas sensors, to monitor critical parameters, such as vibration, sound, temperature, and CO₂ levels. These measurements are crucial for detecting anomalies in engine performance, such as ignition and combustion faults. For combustion engines, temperature sensors detect operational anomalies, including diesel engines operating beyond the normal range of 80 °C to 95 °C and gasoline engines between 90 °C and 110 °C. These readings help identify failures in cooling systems, thermostat valves, or potential coolant leaks. Acoustic sensors identify abnormal noises indicative of issues such as belt misalignment, valve knocking, timing irregularities, or loose parts. Vibration sensors detect displacement issues caused by engine mount failures, cracks in the engine block, or defects in pistons and valves. These sensors can work synergistically with acoustic sensors to enhance fault detection. Additionally, CO₂ and organic compound sensors monitor fuel combustion efficiency and detect failures in the exhaust system. For electric motors, temperature sensors help identify anomalies, such as overloads, bearing problems, or excessive shaft load. Acoustic sensors diagnose coil issues, phase imbalances, bearing defects, and faults in chain or belt systems. Vibration sensors detect shaft and bearing problems, inadequate motor mounting, or overload conditions. The collected data are processed and analyzed to improve engine performance, contributing to reduced greenhouse gas (GHG) emissions and enhanced energy efficiency. This PoC system leverages open-source technology to provide a cost-effective and versatile solution for both research and practical applications. Initial laboratory tests validate its feasibility for real-time data acquisition and highlight its potential for creating datasets to support advanced diagnostic algorithms. Future work will focus on enhancing telemetry capabilities, improving Wi-Fi and cloud integration, and developing machine learning-based diagnostic methodologies for combustion and electric engines. Full article

The COVID-19 pandemic has prompted the need for the development of new biosensors for SARS-CoV-2 detection. Particularly, systems with qualities such as sensitivity, fast detection, appropriate to large-scale analysis, and applicable in situ, avoiding using specific materials or personnel to undergo the test, are highly desirable. In this regard, developing an electrochemical biosensor based on peptides derived from the angiotensin-converting enzyme receptor 2 (ACE2) is a possible answer. To this end, an impedimetric detector was developed based on a graphite electrode surface modified with an ACE2 peptide-mimic. This sensor enables accurate quantification of recombinant 2019-nCoV spike RBD protein (used as a model analyte) within a linear detection range of 0.167–0.994 ng mL⁻¹, providing a reliable method for detecting SARS-CoV-2. The observed sensitivity was further demonstrated by molecular dynamics that established the high affinity and specificity of the peptide to the protein. Unlike other impedimetric sensors, the herein presented system can detect impedance in a single frequency, allowing a measure as fast as 3 min to complete the analysis and achieving a detection limit of 45.08 pg mL⁻¹. Thus, the proposed peptide-based electrochemical biosensor offers fast results with adequate sensitivity, opening a path to new developments concerning other viruses of interest. Full article

This work reports on the assessment of a non-hydrolytic electrochemical sensor for glucose sensing that is developed using functionalized carbon nanotubes (fCNTs)/Co(OH)₂. The morphology of the nanocomposite was investigated by scanning electron microscopy, which revealed that the CNTs interacted with Co(OH)₂. This content formed a nanocomposite that improved the electrochemical characterizations of the electrode, including the electrochemical active surface area and capacitance, thus improving sensitivity to glucose. In the electrochemical characterization by cyclic voltammetry and chronoamperometry, the increase in catalytic activity by Co(OH)₂ improved the stability and reproducibility of the glucose sensor without the use of enzymes, and its concentration range was between 50 and 700 μmol L⁻¹. The sensor exhibited good linearity towards glucose with LOD value of 43.200 µmol L⁻¹, which proved that the Co(OH)₂-fCNTs composite is judicious for constructing cost effective and feasible sensor for glucose detection. Full article

In this study, we have proposed an electrochemiluminescence (ECL) signal amplification system which is based on two-dimensional (2D) flower-like CdS@Co/Mo-MOF composites as a co-reaction accelerator of the g-C₃N₄/S₂O₈²⁻ system for ultrasensitive detection of chlorpromazine hydrochloride (CPH). Specifically, the 2D flower-like Co/Mo-MOF with mesoporous alleviated the aggregation of CdS NPs while simultaneously fostering reactant-active site contact and improving the reactant–product transport rate. This allowed the material to act as a novel co-reaction accelerator, speeding up the transformation of the S₂O₈²⁻ into SO₄^•− and enhancing the cathodic ECL emission of g-C₃N₄. Moreover, the signal probe which was synthesized by coupling the 2D CdS@Co/Mo-MOF and graphitic carbon nitride (g-C₃N₄) achieved the generation of SO₄^•− in situ and reduced energy loss. The results confirmed that the ECL signal was enhanced 6.2-fold and stabilized by CdS@Co/Mo-MOF. Based on the extremely strong quenching effect of chlorpromazine hydrochloride (CPH) on this system, a “signal-off” type sensor was constructed. The sensor demonstrated excellent sensitivity and linear response to CPH concentrations ranging from 1 pmol L⁻¹ to 100 μmol L⁻¹, with a low detection limit of 0.4 pmol L⁻¹ (S/N = 3). Full article

This study intended to understand whether teachers’ perceptions of indoor air quality (IAQ) during classes aligned with the real levels of air pollutants and comfort parameters. For this purpose, an IAQ monitoring survey based on low-cost sensors using a multi-parameter approach was carried out in nine classrooms (a total of 171 monitored classes) in a Portuguese school. In each monitored class, the perception of IAQ reported by the teacher was assessed using a scale from 1 (very bad IAQ) to 10 (very good IAQ). Several exceedances regarding national legislation were found, with temperature being the parameter with a higher percentage of exceedance in all the studied classrooms (46%), followed by PM₁₀ (32%), and then CO₂ (27%). Temperature was found to be the only environmental parameter that was significantly associated with lower IAQ perception reported by the teachers, highlighting that typical pollutants such as CO₂ (which can be identified as stuffy air) did not contribute to the teachers’ perceptions. Full article

Designing and fabricating a highly sensitive non-enzymatic glucose sensor is crucial for the early detection and management of diabetes. Meanwhile, the development of innovative electrode substrates has become a key focus for addressing the growing demand for constructing flexible sensors. Here, a simple one-step laser engraving method is applied for preparing laser-induced graphene (LIG) on polyimide (PI) film, which serves as the sensor substrate. NiCo-layered double hydroxides (NiCo-LDH) are synthesized on LIG as a precursor, utilizing the zeolitic imidazolate framework (ZIF-67), and then reacted with Ni(NO₃)₂ via solvent-thermal methods. The sensitivity of the non-enzymatic electrochemical glucose sensor is significantly improved by employing NiCo-LDH/LIG as the sensing material. The porous and interconnected structure of NiCo-LDH, derived from ZIF-67, enhances the accessibility of electrochemically active sites, while the incorporation of LIG ensures exceptional conductivity. The combination of NiCo-LDH with LIG enables efficient electron transport, leading to an increased electrochemically active surface area and enhanced catalytic efficiency. The fabricated electrode achieves a low glucose detection limit of 0.437 μM and demonstrates a high sensitivity of 1141.2 and 631.1 μA mM⁻² cm⁻² within the linear ranges of 0–770 μM and 770–1970 μM, respectively. Furthermore, the NiCo-LDH/LIG glucose sensor demonstrates superior reliability and little impact from other substances. A flexible integrated LIG-based non-enzymatic glucose sensor has been developed, demonstrating high sensitivity and suggesting a promising application for LIG-based chemical sensors. Full article

The effects of air quality on health and cognition are well documented, but few studies have focused on its impact on emotions, leaving this area underexplored. This study investigates the influence of environmental factors—specifically particulate matter (PM₁, PM_2.5, and PM₁₀) and carbon dioxide (CO₂)—on students’ basic emotions in secondary school classrooms. For the collection of environmental data, we used low-cost sensors, which were carefully calibrated to ensure acceptable accuracy for monitoring air quality variables, despite inherent precision limitations compared to traditional sensors. Emotions were recorded via camera and analyzed using a custom-developed code. Based on these data, we found significant but modest correlations, such as the negative correlation between PM levels and happiness, and positive correlations of CO₂ concentrations with fear and disgust. The regression models explained between 36% and 62% of the variance in emotions like neutrality, sadness, fear, and happiness, highlighting nonlinear relationships in some cases. These findings underscore the need for improved classroom environmental management, including the implementation of real-time air quality monitoring systems. Such systems would enable schools to mitigate the negative emotional effects of poor air quality, contributing to healthier and more conducive learning environments. Future research should explore the combined effects of multiple environmental factors to further understand their impact on student well-being. Full article

This paper presents the results of a study on the characteristics of semiconductor sensors based on thin SnO₂ films modified with antimony, dysprosium, and silver impurities and dispersed double Pt/Pd catalysts deposited on the surface to detect carbon monoxide (CO). An original technology was developed, and ceramic targets were made from powders of Sn-Sb-O, Sn–Sb-Dy–O, and Sn–Sb-Dy-Ag–O systems synthesized by the sol–gel method. Films of complex composition were obtained by RF magnetron sputtering of the corresponding targets, followed by technological annealing at various temperatures. The morphology of the films, the elemental and chemical composition, and the electrical and gas-sensitive properties were studied. Special attention was paid to the effect of the film composition on the stability of sensor parameters during long-term tests under the influence of CO. It was found that different combinations of concentrations of antimony, dysprosium, and silver had a significant effect on the size and distribution of nanocrystallites, the porosity, and the defects of films. The mechanisms of degradation under prolonged exposure to CO were examined. It was established that Pt/Pd/SnO₂:0.5 at.% Sb film with optimal crystallite sizes and reduced porosity provided increased stability of carbon monoxide sensor parameters, and the response to the action of 100 ppm carbon monoxide was G₁/G₀ = 2–2.5. Full article