Search Results (845)

Capacitive ECG sensors in automobiles enable unobtrusive heart rate monitoring as an indicator of a driver’s alertness and health. This paper introduces a capacitive sensor with textile electrodes and provides insights into signal quality and RR duration accuracy. Electrodes of various shapes, sizes, and fabrics were integrated at various positions into the seat back of a driving simulator car seat. Seven subjects completed identical driving circuits with their cardiac signals being recorded simultaneously with textile electrodes and reference Ag-AgCl electrodes. Capacitive ECG signals with observable R peaks (after filtering) could be captured with almost all pairs of textile electrodes, independently of design or placement. Signal quality from textile electrodes was consistently lower compared with reference Ag-AgCl electrodes. Proximity to the heart or even contact with the body seems to be key but not enough to improve signal quality. However, accurate measurement of RR durations was mostly independent of signal quality since 90% of all RR durations measured on capacitive ECG signals had a percentage error below 5% compared to reference ECG signals. Accuracy was actually algorithm-dependent, where a classic Pan–Tompkins-based algorithm was interestingly outperformed by an in-house frequency-domain algorithm. Full article

This study reviews the scientific use of chest-strap wearables, analyzing their advantages and limitations, following PRISMA guidelines. Eligible studies assessed chest-strap devices in adults and reported physiological outcomes such as heart rate, heart rate variability, R–R intervals, or electrocardiographic waveform morphology. Studies involving implanted devices, wrist-worn wearables, or lacking validation against reference standards were excluded. Searches were conducted in PubMed, Scopus, Web of Science, and ScienceDirect for studies published in the last 10 years. The quality of the studies was assessed using the Mixed Methods Appraisal Tool, and results were synthesized narratively. Thirty-two studies were included. The most frequently evaluated devices were the Polar H10 and Zephyr BioHarness 3.0, which showed strong correlations with electrocardiography at rest and during light-to-moderate activity. Reported limitations included motion artefacts, poor strap placement, sweating, and degradation of the skin–electrode interface. None of the devices had CE or FDA approval for clinical use, and most studies were conducted in controlled settings, limiting generalizability. Ergonomic concerns such as discomfort during prolonged wear and restricted mobility were also noted. Overall, chest-strap sensors showed good validity and were widely used in validation studies. However, technical refinements and large-scale field trials are needed for broader clinical and occupational application. This review is registered in PROSPERO and is part of the SIREN project. Full article

This work demonstrates the use of SUS316L stainless steel as a new material for the fabrication of quasi-reference electrodes (QREs) intended to replace conventional reference electrodes (REs) in electrochemical sensors. The present study examined the potentials generated by SUS316L specimens annealed in air at 400 °C and above for 1 h or more. Annealing above 500 °C increased the proportion of Cr in surface oxide films, hence reducing the stability of the potential. Samples annealed at 400 °C for 5 h produced the most stable electrode potential, which was attributed to a higher concentration of Fe in the oxide layer. The potential of such specimens increased by only 28.3 mV between test durations of 24 and 168 h, and potential data acquired at 30 s intervals had a standard deviation of less than 2 µV. Applying a surface treatment prior to immersion in the simulated tap water evidently stabilized the electrode potential, as a consequence of the formation of an inner oxide layer together with an outer layer consisting primarily of iron oxides. Full article

Recent literature reports have shown that individual HEAs, especially those of the AlCoCrFeNi composition system alloyed with appropriately selected elements, exhibit excellent mechanical properties and corrosion resistance, making them promising candidates for replacing conventional materials such as austenitic steels in corrosive environments. Therefore, in the present study, the high-entropy alloy AlCoCrFeNiMo_0.25 was examined and compared with AISI 304L steel and the reference alloy AlCoCrFeNi. The HEA was produced by arc melting in vacuum. The effect of molybdenum addition (5% at.) on the structure, mechanical properties, and corrosion resistance was evaluated. Potentiodynamic polarization and electrochemical impedance spectroscopy tests were carried out in a 3.5% NaCl solution in a three-electrode electrochemical system. The addition of molybdenum to AlCoCrFeNiMo_x alloy additionally caused, along with the BCC phase, the formation of σ phase and FCC phase (less than 1%), as well as changes in the microstructure, leading to the fragmentation of grains and the formation of a mosaic structure. On the basis of nanoindentation tests, it was established that the addition of Mo increases hardness and elastic modulus and improves nanoindentation coefficients H/E and H³/E², as well as an increase in the elastic recovery index while decreasing plasticity index (vs. the reference equiatomic HEA). This indicates the improvement of anti-wear properties with impact loading resistance. In turn, electrochemical tests have shown that the addition of Mo improves corrosion resistance. Corrosion pitting develops in Al- and Ni-rich areas of HEA alloys, as a result of galvanic microcorrosion related to Cr chemical segregation. In general, the addition of 5% Mo results in a fine-grained mosaic structure, which primarily translates into favorable nanoindentation and corrosion properties of the AlCoCrFeNiMo_0.25 alloy. Full article

Intrinsically stretchable polymer ionic conductors (PICs) hold significant application prospects in fields such as flexible sensors, energy storage devices, and wearable electronic devices, serving as promising solutions to prevent mechanical failure in flexible electronics. However, the development of PICs is hindered by an inherent trade-off between mechanical robust and electrical properties. Cellulose, renowned for its high mechanical strength, tunable chemical groups, abundant resources, excellent biocompatibility, and remarkable recyclability and biodegradability, offers a powerful strategy to decouple and enhance mechanical and electrical properties. This review presents recent advances in cellulose-based polymer ionic conductors (CPICs), which exhibit exceptional design versatility for flexible electrodes and strain sensors. We systematically discuss optimization strategies to improve their mechanical properties, electrical conductivity, and environmental stability while analyzing the key factors such as sensitivity, gauge factor, strain range, response time, and cyclic stability, where strain sensing refers to a technique that converts tiny deformations (i.e., strain) of materials or structures under external forces into measurable physical signals (e.g., electrical signals) for real-time monitoring of their deformation degree or stress state. Full article

Intracellular oxidation–reduction (redox) potential is a key factor regulating various physiological phenomena in the cell. Monitoring this potential change is therefore important for understanding physiological homeostasis in cells. Herein, we propose a new approach for the real-time, non-invasive estimation of the redox potential impacting biological metabolism and reactive oxygen species generation. Enzymes, specifically oxidoreductases, play a crucial role in catalyzing redox reactions by facilitating the transfer of electrons and hydrogen atoms between molecules. The redox potential of substrates, such as nicotinamide adenine dinucleotide, is determined by the ratio of its oxidized and reduced forms, while that of enzymes, such as succinate dehydrogenase, is determined using the reference electrode in protein-film voltammetry. Although the standard hydrogen electrode potential is defined as zero under standard conditions, the electrode potential of a reversible hydrogen electrode changes according to the ratio of the hydrogen ions (H⁺) and hydrogen gas (H₂) in the biological fluids, as a reference electrode. The pH is maintained at 7.4 ± 0.1 in the arterial blood and the H₂ that produced by the gut microbiota is measured in the endo-tidal breath for clinical diagnosis. The H₂ in the endo-tidal breath equilibrates arterial blood during gas exchange in the lungs, as well as in whole-body tissues, due to the systemic circulation. In this study, H₂ can be measured in the environmental gas compared to the atmosphere, and may serve as a novel factor for redox potential changes in redox enzymes, impacting biological metabolism and reactive oxygen species generation. Full article

Phase molybdenum disulfide (1T-MoS₂) holds significant promise as an anode material for sodium-ion batteries (SIBs) due to its metallic conductivity and expanded interlayer distance. However, the practical application of 1T-MoS₂ is hindered by its inherent thermodynamic metastability, which poses substantial challenges for the synthesis of high-purity, long-term stable 1T phase MoS₂. Herein, a synergetic ethanol molecule intercalation and electron injection engineering is adopted to induce the formation and stabilization of 1T-MoS₂ (E-1T MoS₂). The obtained E-1T MoS₂ consists of regularly arranged sphere-like ultrasmall few-layered 1T-MoS₂ nanosheets with expanded interlayer spacing. The high intrinsic conductivity and enlarged interlayer spacing are greatly favorable for rapid Na⁺ or e⁻ transport. The elaborated nanosheets structure can effectively relieve volume variation during Na⁺ intercalating/deintercalating processes, shorten transport path of Na⁺, and enhance diffusion kinetics. Furthermore, a novel sodium reaction mechanism involving the formation of MoS₂ nanoclusters during cycling is revealed to produce the higher surface pseudocapacitive contribution to Na⁺ storage capacity, accelerating Na⁺ reaction kinetics, as confirmed by the kinetics analysis and ex-situ structural characterizations. Consequently, the E-1T MoS₂ electrode exhibits an excellent sodium storage performance. This work provides an important reference for synthesis and reaction mechanism analysis of metastable metal sulfides for advanced SIBs. Full article

Wearable electroencephalography (EEG) enables brain monitoring in real-world environments beyond clinical settings; however, the relaxed constraints of the acquisition setup often compromise signal quality. This review examines methods for artifact detection and for the identification of artifact categories (e.g., ocular) and specific sources (e.g., eye blink) in wearable EEG. A systematic search was conducted across six databases using the query: (“electroencephalographic” OR “electroencephalography” OR “EEG”) AND (“Artifact detection” OR “Artifact identification” OR “Artifact removal” OR “Artifact rejection”) AND “wearable”. Following PRISMA guidelines, 58 studies were included. Artifacts in wearable EEG exhibit specific features due to dry electrodes, reduced scalp coverage, and subject mobility, yet only a few studies explicitly address these peculiarities. Most pipelines integrate detection and removal phases but rarely separate their impact on performance metrics, mainly accuracy (71%) when the clean signal is the reference and selectivity (63%), assessed with respect to physiological signal. Wavelet transforms and ICA, often using thresholding as a decision rule, are among the most frequently used techniques for managing ocular and muscular artifacts. ASR-based pipelines are widely applied for ocular, movement, and instrumental artifacts. Deep learning approaches are emerging, especially for muscular and motion artifacts, with promising applications in real-time settings. Auxiliary sensors (e.g., IMUs) are still underutilized despite their potential in enhancing artifact detection under ecological conditions. Only two studies addressed artifact category identification. A mapping of validated pipelines per artifact type and a survey of public datasets are provided to support benchmarking and reproducibility. Full article

Bio field-effect transistors (BioFETs) have attracted attention for their ability to rapidly detect physiological data with a simple structure. While conventional BioFETs offer high sensitivity, they often require reference electrodes or involve complex fabrication processes. A recently proposed bulk junctionless BioFET (Bulk JL-BioFET) features a simple fabrication process to address these issues. This structure utilizes a depletion region formed by a p-n junction, as the active layer is directly in contact with a substrate of the opposite type. As a result, the device can operate effectively with only two terminals—drain and source—without the need for a reference electrode. In this study, we propose a novel Bulk JL-BioFET, incorporating a doped field stop layer and an asymmetric source/drain structure, and verify its performance through simulations. The doped field stop layer blocks the electric field expansion, enhancing channel modulation, while the asymmetric source/drain structure promotes electron injection, reducing the on-off swing voltage and turn-on voltage. This improves the electrical performance, enabling lower power consumption and higher sensitivity. Simulation results show that the combination of these two novel features results in a sensitivity increase of approximately 30-fold. Moreover, high sensitivity was observed below the turn-on voltage region for all the structures when analyzing the sensitivity with overdrive voltage, identifying the optimal operating conditions. This study suggests that the combination of the doped field stop layer and asymmetric source/drain structure is an effective design strategy to maximize the sensing performance of BioFETs while minimizing power consumption. Full article

The complex interference created by several sources for pipelines has not been sufficiently studied. In this study, four types of interference sources were monitored and analyzed. AC voltage monitoring, DC potential monitoring, current density monitoring, and excavation observation and measurement for test pieces and the decouplers were employed to assess the AC/DC interference of one real buried pipeline in situ. The peak value obtained from the second measurement at Pile 33 decreased from 1341.8 V to 143.7 V, indicating that the 1341.8 V in the first measurement may be caused by a sudden grounding of the electrode, while the 143.7 V may be caused by the normal induced voltage. The most negative DC interference potential between the pipeline and the Cu/CuSO₄ reference electrode was −11.946 V. The most positive DC interference potential between the pipeline and the Cu/CuSO₄ reference electrode was 4.862 V. Pile 3 had a maximum DC current density of 240 mA/m², and Pile 4 had a maximum AC current density of 0.615 A/m². After excavating the test piece at Pile 3, the point with maximum DC interference, there were obvious pitting corrosion characteristics, and the corrosion products were mainly γ-FeOOH and Fe₃O₄. It indicated that the coupling of long-term higher positive DC current density or (DC potential) and short-term higher transient AC voltage or (AC current density) may lead to corrosion. After excavating the test piece at the point with maximum AC interference, namely, Pile 4, there were no significant AC or DC corrosion characteristics. This finding suggested that the combination of long-term low AC current voltage or (low AC current density) and long-term more negative low DC current density or (DC potential) did not result in obvious corrosion. The decouplers in this measurement significantly reduced AC interference above 2 V, but the isolation of transient AC shocks and AC interference below 2 V were not significant. During analysis of AC and DC interference, in addition to considering the value of the interference, the duration time of the interference was also an important factor. Instantaneous sharp peaks cannot represent the long-term average voltage or potential current density. The average value should be used as the main basis for judgement, and the instantaneous value should be used as the secondary basis for judgement. Full article

Background: Intuitive inquiry meditation (Can-Hua-Tou) is a unique mental practice which differs from relaxation-based practices by continuously demanding intuitive inquiry. It emphasizes the doubt-driven self-interrogation, also referred to as Chan/Zen meditation. Nonetheless, its electrophysiological signature remains poorly characterized. Methods: We recorded 128-channel EEG from 20 male Buddhist monks (5–28 years Can-Hua-Tou experience) and 18 male novice lay practitioners (<0.5 year) during three counter-balanced eyes-closed blocks: Zen inquiry meditation (ZEN), a phonological control task silently murmuring “A-B-C-D” (ABCD), and passive resting state (REST). Power spectral density was computed for alpha (8–12 Hz), beta (12–30 Hz) and gamma (30–45 Hz) bands and mapped across the scalp. Mixed-design ANOVAs and electrode-wise tests were corrected with false discovery rate (p < 0.05). Results: Alpha power increased globally with eyes closed, but condition- or group-specific effects did not survive FDR correction, indicating comparable relaxation in both cohorts. In contrast, monks displayed a robust beta augmentation, showing significantly higher beta over parietal-occipital leads than novices across all conditions. The most pronounced difference lay in the gamma band: monks exhibited trait-like fronto-parietal gamma elevations in all three conditions, with additional, though sub-threshold, increases during ZEN. Novices showed negligible beta or gamma modulation across tasks. No significant group × condition interaction emerged after correction, yet only experts expressed concurrent beta/gamma amplification during meditative inquiry. Conclusions: Long-term Can-Hua-Tou practice is associated with frequency-specific neural adaptations—stable high-frequency synchrony and state-dependent beta enhancement—consistent with Buddhist constructs of citta-ekāgratā (one-pointed concentration) and vigilance during self-inquiry. Unlike mindfulness styles that accentuate alpha/theta, Chan inquiry manifests an oscillatory profile dominated by beta–gamma dynamics, underscoring that different contemplative strategies sculpt distinct neurophysiological phenotypes. These findings advance contemplative neuroscience by linking intensive cognitive meditation to enduring high-frequency cortical synchrony. Future research integrating cross-frequency coupling analyses, source localization, and behavioral correlates of insight will further fully delineate the mechanisms underpinning this advanced contemplative expertise. Full article

Sulfides are frequently encountered in natural mineral water and different wastewater streams, and their presence significantly impedes subsequent water treatment or utilization. Sulfide removal, or at least its reduction, can be accomplished in different ways, but there is one straightforward method where sulfide is captured on a carbon-based sorbent, with the consequent sorbent regeneration producing electricity in liquid fuel cell mode. This multi-functional approach combines sulfide removal, energy generation, and water pre-treatment for various applications. The present work aims to show sulfide removal from sulfide-containing wastewater streams from alcohol and beverage manufacturing. The clean water could be used for biogas production. Sorbent regeneration was performed in fuel cell mode and was accompanied by electricity production. The experiments, conducted in a liquid-phase fuel cell, used electrode compartments that were separated by an anion-exchange membrane. Electroconductive charcoal, produced via the pyrolysis of residues from tire production and doped with zinc oxide, was used as a sorbent. The experimental treatments of vinasse, whey, and stillage for sulfide removal by this method show the sustainable performance of the sorbent for up to twelve consecutive runs. The biogas yield produced from vinasse was increased more than three times for the treated substrate compared to the reference case. Full article

Self-healing is imperative for the restoration of the insulation state of metallized film capacitors following breakdown during operation, thereby ensuring the safe and reliable functioning of the capacitors. Temperature is an important factor affecting the self-healing behavior of film capacitor dielectrics, but the mechanism is currently unclear. To investigate the effects of temperature and dielectric matrix on self-healing behavior, polyetherimide (PEI), cycloolefin copolymer (COC), and biaxially oriented polypropylene (BOPP) were selected as research subjects. A systematic study was conducted to examine the self-healing performance at 80, 120, and 150 °C, as well as the effect of self-healing on insulation and energy storage performance. The results showed that as the temperature increased, the capacitance of PEI decreased by 11.90%, 23.00%, and 37.88%, respectively. COC decreased by 11.76%, 7.63%, and 12.18%, respectively, while BOPP decreased by 8.75% and 9.67%, respectively. The accumulation of breakdown holes formed by self-healing decreases, the area of evaporated electrodes decreases, and the boundaries between the evaporated electrode areas formed by self-healing and the surrounding electrodes become more distinct. Furthermore, COC exhibits high dielectric strength, low dielectric loss, and self-healing properties comparable to BOPP at 150 °C, suggesting significant application potential. This research work is of great reference value for establishing the theoretical relationship between the chemical composition of dielectrics and their self-healing ability, and is of great significance for ensuring the safe and reliable operation of capacitors. Full article

Motor impairments significantly affect individuals’ ability to perform activities of daily living, reducing autonomy and quality of life. In response to this, robot-assisted rehabilitation has emerged as an effective and practical solution, enabling controlled limb movements and supporting functional recovery. This study presents the development of an upper-limb exoskeleton designed to assist rehabilitation by integrating neurophysiological signal processing and real-time control strategies. The system incorporates a proportional–derivative (PD) controller to execute cyclic flexion and extension movements based on a sinusoidal reference signal, providing repeatability and precision in motion. The exoskeleton integrates a brain–computer interface (BCI) that utilizes electroencephalographic signals for therapy selection and engagement enabling user-driven interaction. The EEG data extraction was possible by using the UltraCortex Mark IV headset, with electrodes positioned according to the international 10–20 system, targeting alpha-band activity in channels O1, O2, P3, P4, Fp1, and Fp2. These channels correspond to occipital (O1, O2), parietal (P3, P4), and frontal pole (Fp1, Fp2) regions, associated with visual processing, sensorimotor integration, and attention-related activity, respectively. This approach enables a more adaptive and personalized rehabilitation experience by allowing the user to influence therapy mode selection through real-time feedback. Experimental evaluation across five subjects showed an overall mean accuracy of 86.25% in alpha wave detection for EEG-based therapy selection. The PD control strategy achieved smooth trajectory tracking with a mean angular error of approximately 1.70°, confirming both the reliability of intention detection and the mechanical precision of the exoskeleton. Also, our core contributions in this research are compared with similar studies inspired by the rehabilitation needs of stroke patients. In this research, the proposed system demonstrates the potential of integrating robotic systems, control theory, and EEG data processing to improve rehabilitation outcomes for individuals with upper-limb motor deficits, particularly post-stroke patients. By focusing the exoskeleton on a single degree of freedom and employing low-cost manufacturing through 3D printing, the system remains affordable across a wide range of economic contexts. This design choice enables deployment in diverse clinical settings, both public and private. Full article

The convergence of flexible electronics and miniaturized ultrasound transducers has accelerated the development of wearable ultrasound devices, offering innovative solutions for continuous, non-invasive physiological monitoring and disease diagnosis. This review systematically examines the recent progress in the field, focusing on three key aspects: physical principles, device design, and clinical applications. From the perspective of physical principles, we provide an in-depth analysis of the fundamental theories underlying ultrasound imaging, including acoustic wave propagation in biological tissues, interface reflection mechanisms, and Doppler effects. In terms of device design, we compare technical approaches for rigid and flexible ultrasound transducers, with particular emphasis on innovative designs for flexible transducers. The key developments discussed include optimization of piezoelectric materials, the fabrication of stretchable electrodes, and advances in flexible encapsulation materials. Regarding clinical applications, we categorize the use cases by anatomical region and illustrate their diagnostic value through representative examples, demonstrating their utility in disease detection, health monitoring, and sports medicine. Finally, we identify critical challenges such as signal stability, coupling material compatibility, and long-term wearability, while outlining future directions including AI-assisted diagnosis and multifunctional integration. This review aims to provide a comprehensive reference for both fundamental research and clinical translation of wearable ultrasound technologies. Full article