Short Response Time Research Articles

Recyclable Chitosan-Modified Cellulose Fiber Porous Structure for Sensitive and Robust Moisture-Driven Actuators and Automatic Cooling Textiles.

Moisture-driven actuators featuring programmable stimuli-responsiveness and a rapid response have garnered substantial research attention. Cellulose-based actuators face challenges, including prolonged and unstable responsiveness, along with inadequate interfacial bonding. Herein, we developed a bilayer structured moisture actuator by integrating multiscale cellulose fibers with chitosan. The protonated chitosan forms strong electrostatic attractions with negatively charged cellulose nanofibrils (CNF), achieving a robust interfacial interaction. Leveraging the hierarchically porous structure and varying hygroscopicity of microfibrillated cellulose (MFC) and CNF, the film establishes an effective wettability gradient, enabling a stable and rapid moisture actuation performance. The bilayer film exhibits large deformation toward moisture with a bending angle of 60°, a short response time of 12 s, good stability over 50 wetting and drying cycles, and promising recyclability. Harnessing these advantageous properties, the bilayer film was demonstrated for its applications in automatic cooling textiles, contactless electrical switches, and artificial moisture-activated muscles, showing great potential for practical use.

Carbazole-Based Dual-Band Electrochromic Polymers: The Effect of Linkage Sites on Electrochromic Performance.

Dual-band electrochromic (EC) materials are expected to be utilized as building materials for energy saving, but their cycle stability is still an obstacle. Here, two D-A conjugated polymers, PDPPCz36 and PDPPCz27, based on diketopyrrolopyrrole and carbazole linked with different sites, are synthesized. Both of them exhibit dual-band EC behaviors with a dark blue color in the neutral state and high absorption in the near-infrared (NIR) region when oxidized. However, PDPPCz36 exhibits better cycle stability and a shorter response time than PDPPCz27. In the visible (VIS) region, the PDPPCz36 film exhibits an initial light modulation range (ΔT) of 43.0% and that of the PDPPCz27 film is 41.3%. After 100 cycles of redox, the ΔT of the PDPPCz36 film declines by 32%, while that of PDPPCz27 attenuates by more than 50%. A similar tendency is evident in the NIR region. Moreover, PDPPCz36 shows subsecond colored switch times both in the VIS (0.4 s) and NIR (0.7 s) regions, while those of PDPPCz27 are 2.1 and 1.6 s, respectively. Further research suggests that 3,6-linked carbazoles in PDPPCz36 simultaneously inhibit the side reaction and film aggregation, which leads to better redox stability and shorter response time in both EC tests and devices.

Implementación de un Dispositivo Inteligente para la Asistencia de Personas con Discapacidad Visual en Entornos Universitarios

This project arises in response to the growing global need for inclusive technological solutions aimed at improving the quality of life of people with visual impairments. The motivation is based on addressing the specific barriers these individuals face, with a particular focus on university environments. The methodology adopted focuses on the convergence of web services and networked communication technologies, seeking to promote the autonomy and safety of visually impaired people. A distinctive aspect of this project is the implementation of low power consumption and long-range technology, marking a pioneering approach in this field, which not only addresses the immediate need for inclusive solutions; but contributes to technological advancement by introducing efficient and long-range solutions. Through testing, very short response times are achieved in terms of identifying dangerous movements such as falls and detecting nearby objects, while character recognition still requires further refinement. The key innovation lies in the effective convergence of technologies, setting a new standard for inclusive and sustainable solutions. In other words, this project not only responds to a pressing need, but also marks a significant milestone in improving inclusion for the visually impaired, highlighting its relevance at the local level and contributing to global progress in this crucial field.

Synergistic Coordination Effect and Metal-Support Interaction Engineering of Single-Atom Mn-N2 Sites for Boosting Sensitive and Selective Dopamine Biosensing in Human Serum.

Coordination environment of metal atoms is core for designing high-performance single-atom catalysts (SACs), while metal-support interaction also has an important effect on structure-function relationship. Nevertheless, the interaction effect of metal-support is mostly ignored. Through synergistic regulation of coordination environment and metal-support interaction, Mn SAC with atom-dispersed Mn-N2 sites on dopamine (DA) support is synthesized for sensitive and selective DA oxidation based on theoretical calculations and experimental explorations. MnN2 presents the more optimal catalytic site for DA oxidation than other coordination conditions, enhancing sensitivity including a wide range, a low limit of detection, and particularly a very low catalytic potential. The construction of Mn-N2 active sites on DA carbon promotes the coupling between Mn metal atoms and DA support, decreasing work function, facilitating electron exchange, shortening response time, and boosting selectivity. Both the catalytic mechanism of Mn SAC toward DA and the relation construction of catalyst's structure and catalytic function are established.

Arrayed multi-layer piezoelectric sensor based on electrospun P(VDF-TrFE)/ZnO with enhanced piezoelectricity

Flexible pressure sensors can maintain good pressure sensing capabilities even under arbitrary degrees of deformation, which are widely used in fields such as robotic perception, physiological signal detection and wearable electronics. Currently, piezoelectric-based flexible pressure sensors face significant limitations in terms of large-area, high-sensitivity, and high-resolution pressure detection. Targeted research efforts primarily focus on enhancing the performance of piezoelectric sensors by optimizing the properties of the sensitive layer piezoelectric material and modulating device structural design. This study introduces a novel multilayer array design for flexible composite piezoelectric sensors. A high-voltage electrospinning selective deposition process is proposed to fabricate arrayed nanofiber mats. Patterned electrospun films can be automatically patterned by patterned AgNW electrodes, which allows manual alignment of patterns for subsequent stacking. Compared to sensor based on P(VDF-TrFE) prepared under the same conditions, the sensitivity of the multi-layer P(VDF-TrFE)/ZnO sensor increased from 2.82 mV/kPa to 8.30 mV/kPa, providing an effective approach for highly sensitivity wearable devices with short response time (∼5 ms).

Preparation of aerogels with SBS@rGO structure by Pickering emulsion method for innovative applications in pressure sensors

Pressure sensors based on graphene conductive fillers show great promise for application in the field of smart wearable devices. The SBS@rGO structured aerogel sensors covered herein were prepared by the Pickering emulsion method based on a solution of styrene-butadiene-styrene (SBS) and reduced graphene oxide (rGO) dispersion. The mechanical properties of SBS@rGO aerogel were tested with 100 independent loading-unloading cycles in a graded compressive strain range of 10–40 %. The results indicate that the SBS@rGO aerogel have fast and slightly destructive resilience after unloading at low compressive strains (ε ≤ 30 %). Moreover, the presence of rGO endowed SBS@rGO with pressure sensing properties such as high electrical conductivity (2.294 S/m), high sensitivity (0.016 kPa−1 at 6.36–100 kPa), short signal response time (60 ms) and recovery time (30 ms). The SBS@rGO pressure sensors were integrated into shoe soles to simulate walking scenes, whose response signals had excellent reproducibility and could be differentiated according to three different walking states. The potential and feasibility of SBS@rGO aerogel as wearable flexible pressure sensors has been demonstrated.

Laser-induced graphene-based aptasensor for the selective detection of Escherichia coli in urine samples

A Laser-Induced Graphene-based (LIG) electrode covalently functionalized with an aptamer (P12-55) was used to develop an aptasensor detecting Escherichia coli in urine samples. Recent strides in material science have spotlighted LIG for exceptional attributes like robust mechanical resistance, superior conductivity, extensive surface area, and facile synthesis/patterning on various polymeric substrates. Variations in the aptasensor charge transfer resistance upon interaction with bacterial cells were evaluated by electrochemical impedance spectroscopy. Tests in phosphate buffer saline solution showed the aptasensor linear response for E. coli between 100 and 103 CFU/mL. The sensor proved to be selective for E. coli as a negligible response was observed in the presence of Staphylococcus aureus or Pseudomonas aeruginosa. Finally, the sensor was calibrated in urine samples spiked with a known concentration of E. coli cells. Its characteristics make the aptasensor viable for low-cost and portable devices identifying pathogenic microorganisms at the point-of-need. Due to the short response time (about 30 min), we believe that these sensing devices may significantly improve control and management of urinary tract infections.

An Adaptive Controller with Disturbance Observer for Underwater Vehicle Manipulator Systems

Dynamic control of underwater vehicle manipulator systems (UVMSs) is the key part of underwater intervention tasks. In this paper, we propose an adaptive controller with a disturbance observer that mainly consists of two parts: the first part is the adaptive control law that estimates the changes in the center of mass (COM) and the center of buoyancy (COB) of the vehicle, and the second part is the nonlinear disturbance observer that estimates the external disturbance and model uncertainties. To attenuate the overestimation problem, a damping term is introduced to the adaptive law. The stability of the proposed method is proven on the basis of Lyapunov theory. We develop three scenarios on the Simurv platform and illustrate the effectiveness of the proposed method with a short response time and high tracking performance.

Fabrication of a novel non-enzymatic glucose sensor based on ruthenium supported by a combination of PBA nanocubes and MOF nanosheets

The development of novel catalysts with high catalytic activity is of high importance of electrochemical non-enzymatic glucose sensing. Herein, a sensitive non-enzymatic electrochemical sensor (Ru@NiCo-MOF/NiFe-PBA) has been synthesized using a fast, simple and eco-friendly method. The high stability of PBA and the large specific surface area (two-dimensional nanosheet structure) of MOF support the excellent electrochemical performance, while the incorporation of the highly active metal Ru enhances the electrochemical activity even more. The results reveal that the sensitivities of the sensor are 1070.77 and 487.62 μA mM−1 cm−2, corresponding to linear ranges of 0.01–0.67 mM and 0.67–5.07 mM, respectively. Meanwhile, the sensor has a low detection limit (0.446 μM) and a short response time (2 s), making it a strong candidate for non-enzymatic glucose sensors. The successful detection of glucose in saliva further demonstrates its potential for practical applications. Therefore, Ru@NiCo-MOF/NiFe-PBA will make an impact in the field of glucose monitoring and detection.

Au-sensitized metal–organic framework-derived indium-doped zinc oxide for highly enhanced trimethylamine sensing

Preparation of a gas sensor capable of rapidly and accurately detecting trimethylamine is crucial for environmental monitoring, food safety and human health. In this study, Au-In-ZnO with an irregular nanoparticle structure was prepared using simple metal–organic-framework synthesis method and in-situ reduction process. The Au-In-ZnO sensor exhibited a high response of 260.2 to 100 ppm trimethylamine at 250 °C, which is 32 times higher than that of pristine ZnO (350 °C), with the optimal operating temperature lowered by 100 °C. Meanwhile, the sensor had a short response time (2 s), enabling it to quickly react to leaked trimethylamine during practical applications. Additionally, the sensor also possessed low detection limit (0.3 ppm, Rair/Rgas=2.0), high selectivity, excellent moisture resistance, good repeatability, and long-term stability. The mechanism of gas-sensitive properties enhancement was analyzed in combination with the conduction mechanism of hypervalent ions and the electronic and chemical sensitization of noble metals. This study provides a potential gas-sensitive material for the efficient measurement and rapid evaluation of trimethylamine.

Dual Cross-Linked Networks Reinforced Polyimide Foams with Outstanding Piezoelectric Properties and Heat Resistance Performance.

The application of traditional isocyanate-based polyimide (PI) foams is highly hindered due to limited flame retardancy, poor mechanical properties, and relatively single functionality. Herein, we propose an effective method to fabricate dual cross-linked polyimide/bismaleimide (PI-BMI) foams with outstanding heat resistance and enhanced mechanical properties by incorporating bis(3-ethyl-5-methyl-4-maleimidophenyl)methane (ME-BMI) as the interpenetrating network. The results show that the prepared PI-BMI composite foams exhibit enhanced mechanical properties with lightweight characteristics (23-80 kg·m-3). When the ME-BMI loading reached 120 wt %, the tensile and compressive strength of PI-BMI composite foam can reach 1.9 and 7.8 MPa, which are 9.6 and 63.3 times higher than that of pure PI foam, respectively. In comparison with PIF-0, the 10% heat loss temperature (Td,10%) of PIF-90 improved by 156 °C. Moreover, the PI-BMI foam piezoelectric sensor containing fluorine groups presents a short response time (14.22 ms), high sensitivity (0.266 V/N), and outstanding stability (10 000 cycles). Besides, the sensor can accurately monitor human activity in different states. This work provides a promising strategy for designing multifunctional PI foams, making them suitable for applications in aerospace and microelectronics.

Integrated mid-infrared sensing and ultrashort lasers based on wafer-level Td-WTe2 Weyl semimetal

There is an urgent need for infrared (IR) detection systems with high-level miniaturization and room-temperature operation capability. The rising star of two-dimensional (2D) semimetals with extraordinary optoelectronic properties can fulfill these criteria. However, the formidable challenges with regard to large-scale patterning and substrate-selective requirements limit material deposition options for device fabrication. Here, we report a convenient and straightforward eutectic-tellurization transformation method for the wafer-level synthesis of 2D type-II Weyl semimetal WTe2. The non-cryogenic WTe2/Si Schottky junction device displays an ultrawide detection range covering 10.6 μm with a high detectivity of ∼109 Jones in the mid-infrared (MIR) region and a short response time of 1.3 μs. The detection performance has surpassed most reported IR sensors. On top of that, on-chip device arrays based on Schottky junction display an outstanding MIR imaging capability without cryogenic cooling, and 2D WTe2 Weyl semimetal can serve as a saturable absorber for stable Q-switched and mode-locked laser operation applications. Our work offers a viable route for wafer-scale vdW preparation of 2D semimetals, showcasing their intriguing potential in on-chip integrated MIR detection systems and ultrafast laser photonics.

Mn Doped MoO3 with Self-Assembled Nanoflowers Structure and Enhanced Gas Sensing Properties to Triethylamine

Increasing quality of life requires low power consumption and reliable gas sensing technology for real-time monitoring of the environment. Herein, based on the principle of ion compensation and charge compensation, Mn-doped MoO3 self-assembled nanoflowers were designed and prepared, and their gas-sensing performance were studied. Benefiting from abundant defective sites and surface chemical state changes, the sensor exhibits superior characteristics for triethylamine detection, including ultrahigh response (436.9), short response time (7 s), small detection limit (1 ppm), and remarkable selectivity. The gas-sensitive mechanism of M-MoO3 was explained from the points of view of charge compensation and ion compensation, and it was proved that the incorporation of Mn into MoO3 was an effective way to improve its gas sensitivity. This work provides a potential strategy for widespread triethylamine detection and provides new ideas for the design of high-performance sensors.

Regulation of receptor function in NiCo2O4-SnO2 heterojunction for H2S detection at room temperature

In recent years, the World Health Organization has increasingly emphasized air quality in production environments, leading to heightened societal demands for monitoring of pollutant gases at room temperature. Traditional semiconductor gas-sensitive materials, such as tin oxide (SnO2), have their gas-sensing performance largely limited by their receptor functions, resulting in common issues like low response and poor recovery at room temperature. Spinel-type bimetallic oxides, such as nickel cobaltate (NiCo2O4), offer a unique solution due to their rich adsorption sites on the surface, which provide distinctive receptor functions for detecting toxic gases at room temperature. Herein, NiCo2O4 is synthesized via a one-step hydrothermal method, with a porous spherical cluster structure, and combined with SnO2 to form a heterojunction. The NiCo2O4-SnO2 heterojunction film gas sensor exhibits excellent gas-sensing performance for H2S at room temperature, including high response, short response time, good repeatability, and selectivity. Additionally, the unique receptor functions of the NiCo2O4 were analyzed through first-principles calculations, revealing a semiconductor p-n conversion phenomenon in the presence of H2S gas. The composite also demonstrates a conversion from p-n heterojunction to n-n homojunction during the sensing process, enhancing its gas-sensing performance. This work not only addresses the receptor function limitations of traditional gas-sensitive semiconductor but also provides a feasible approach for controlling carrier types in semiconductors.

A systematic study on the crystal facets-dependent TEA sensing properties of designed anatase {001 and 101} and rutile {110} facets TiO2

Triethylamine (TEA), a toxic and explosive volatile organic compound (VOC) gas, is hazardous to human health and the environment. Therefore, it is crucial to develop crystal-faceted TEA gas sensors with improved sensitivity and rapid detection capabilities. In this study, TiO2 nanocrystal sensors with different crystal facets of anatase {101} and {001} and rutile {110} were synthesized using the hydrothermal method. The nanomaterials underwent characterization through XRD, SEM, TEM, XPS, and BET analysis. The results revealed that the materials exhibited bipyramid anatase {101} facet, nanorod anatase {001} facet, and rutile {110} facet. The sensors demonstrated superior gas sensing performance in the following order: {101} > {110} > {001} facets to 100 ppm TEA gas at 240 °C. The sensors also exhibited short response and recovery times, low detection limits, excellent stability, repeatability, and selectivity. The enhanced sensing properties of {101} faceted TiO2 can be ascribed to the bipyramid structure and crystal facets with higher adsorbed oxygen peak specific area, which provide numerous active sites and improved extra oxygen-active site species. This study offers valuable insight into the design mechanism to enhance the TEA response of {101} faceted TiO2 and further contributes to our understanding of the sensitivity of crystal faceted sensors.

Co-doped ZnO nanofibers fabricated via electrospinning for rapid and ppb-level detection of listeria biomarker 3-hydroxy-2-butanone

Listeria monocytogenes, a food-borne pathogen capable of releasing biomarker 3-hydroxy-2-butanone (3H-2B), generally causes a serious threat to human health. Developing 3H-2B gas sensor with excellent performance is of great significance in the diagnosis and prevention of Listeria. Here, we have successfully fabricated Co-doped ZnO nanofibers gas sensor via an electrospinning method, which can be well used for real-time monitoring of Listeria. The results show that the Co-doped ZnO nanofibers have a wurtzite crystal structure and a nanofiber-like morphology with a diameter of 62 nm. The band gap (3.15 eV) of the Co-doped ZnO is significantly narrower than that of the pure ZnO (3.25 eV). The response (168) of the 0.5%Co-doped ZnO based sensor to 100 ppm 3H-2B at 305 °C is 5.37 times greater than that of the pure ZnO (31.3), with a high selectivity, a lower detection limit (100 ppb) and a short response time of 1 s. The enhanced gas sensing mechanism is ascribed to the depletion layer on the ZnO surface, a superposition effect of interface barrier, and the narrowed band gap of the ZnO.

Study on electro-optical dual-control color-changing and energy-storage device based on Mo-WO3 and Al-TiO2 thin film electrode

Under optical and electrical control, a multifunctional electro-optical dual-control color-changing and energy-storage device not only realizes quick color conversion, but also achieves good storage performance. In this work, Mo doped WO3 (Mo-WO3) films were synthesized through one-step hydrothermal method and N719/Al doped TiO2 (N719/Al-TiO2) films were synthesized by hydrothermal and dip-dyeing method. Eventually, choosing Mo-WO3 as cathode and N719/Al-TiO2 film as anode, a multifunctional electro-optical dual-control Mo-WO3@N719/Al-TiO2 color-changing and energy-storage device was constructed. Under electrical control, the device shows excellent coloration efficiency (73.99 cm2/C), fast color switching rate (coloring/ bleaching time is 3.6 s/1.4 s), obviously improved area capacitance (about 82.6 mF/cm2) and excellent cycle stability. Under optical control, the device also shows shortened response time (coloring/ bleaching is 64.3 s/143.4 s), outstanding coloration efficiency (70.49 cm2/C), better area capacitance (about 58.6 mF/cm2) and excellent photoelectric conversion efficiency (10.56 %).

Improved Performance of the Permanent Magnet Synchronous Motor Sensorless Control System Based on Direct Torque Control Strategy and Sliding Mode Control Using Fractional Order and Fractal Dimension Calculus

This article starts from the premise that one of the global control strategies of the Permanent Magnet Synchronous Motor (PMSM), namely the Direct Torque Control (DTC) control strategy, is characterized by the fact that the internal flux and torque control loop usually uses ON–OFF controllers with hysteresis, which offer easy implementation and very short response times, but the oscillations introduced by them must be cancelled by the external speed loop controller. Typically, this is a PI speed controller, whose performance is good around global operating points and for relatively small variations in external parameters and disturbances, caused in particular by load torque variation. Exploiting the advantages of the DTC strategy, this article presents a way to improve the performance of the sensorless control system (SCS) of the PMSM using the Proportional Integrator (PI), PI Equilibrium Optimizer Algorithm (EOA), Fractional Order (FO) PI, Tilt Integral Derivative (TID) and FO Lead–Lag under constant flux conditions. Sliding Mode Control (SMC) and FOSMC are proposed under conditions where the flux is variable. The performance indicators of the control system are the usual ones: response time, settling time, overshoot, steady-state error and speed ripple, plus another one given by the fractal dimension (FD) of the PMSM rotor speed signal, and the hypothesis that the FD of the controlled signal is higher when the control system performs better is verified. The article also presents the basic equations of the PMSM, based on which the synthesis of integer and fractional controllers, the synthesis of an observer for estimating the PMSM rotor speed, electromagnetic torque and stator flux are presented. The comparison of the performance for the proposed control systems and the demonstration of the parametric robustness are performed by numerical simulations in Matlab/Simulink using Simscape Electrical and Fractional-Order Modelling and Control (FOMCON). Real-time control based on an embedded system using a TMS320F28379D controller demonstrates the good performance of the PMSM-SCS based on the DTC strategy in a complete Hardware-In-the-Loop (HIL) implementation.

DFT Study on the Second-Order NLO Responses of 2-Phenyl Benzoquinoline Ir(III) Complexes by Substituents and Redox Effects.

Metal complexes have received extensive attention in nonlinear optical (NLO) materials because of their advantages, such as shorter response times and more flexible structural properties. Density functional theory is used in investigating the geometric structures, electronic structures, charge centroid, and first hyperpolarizability (βtot) of a series of selected 15 coordinated Ir(III) complexes. The substitute effect and one-electron redox process effects on the structures and properties of 15 coordinated Ir(III) complexes are considered. When the electron-withdrawing group is introduced into the ligand, the HOMO-LUMO energy gap decreases and the βtot value increases, positively correlating with the electron-withdrawing ability. The single electron redox process can also improve the NLO responses of complexes, especially the reduction process. The βtot value of complex 4- is the largest, 2078 times higher than that of complex 4. The analysis shows that the variation of NLO responses of complexes is ascribed to the change of electronic structures and the charge transfer modes induced by the ligand modification and redox process, which are considered to be two effective methods in enhancing the NLO responses of 2-phenyl benzoquinoline Ir(III) complexes. This study aims to offer design insights into high-performance nonlinear optical materials.

Sensitivity-enhanced optical fiber sensor based on the Vernier effect for detection of ammonia in water

A sensitivity-enhanced optical fiber sensor for the detection of dissolved ammonia in water based on the Vernier effect is proposed and demonstrated. The sensor comprises a sensing Fabry-Perot interferometer (S-FPI) and a reference Fabry-Perot interferometer (R-FPI) in parallel. The S-FPI is an open cavity fabricated by the dislocation welding of single-mode fiber(SMF), which is filled with a mixture of ultraviolet-curable resin NOA 170 and Oxazine 170 perchlorate (O17). The R-FPI is a sealed cavity, which is constructed by fusion splicing of SMF and hollow core fiber (HCF). The proposed sensor is based on the chemical reaction between the dissolved ammonia and O17. This chemical reaction alters the refractive index (RI) of the S-FPI, resulting in a wavelength shift of the reflected spectrum. The two interferometers exhibit a nearly identical free spectral range (FSR), thereby enabling the generation of the Vernier effect, which markedly enhances the ammonia sensitivity of the sensor. Experimental results indicate that the sensor sensitivity is 0.34 nm/ppm in the dissolved ammonia range of 5-40 ppm, which is approximately 9.1 times that of the single S-FPI. The proposed sensor exhibits both good repeatability and a short response time, in addition to selectivity for the detection of ammonia.