Anisotropic sensing based on single ReS2flake for VOCs discrimination.

Selective and sensitive detection of volatile organic compounds (VOCs) holds paramount importance in real-world applications. This study proposes an innovative approach utilizing a single ReS2field-effect transistor (FET) characterized by distinct in-plane anisotropy, specifically tailored for VOC recognition. The unique responses of ReS2, endowed with robust in-plane anisotropic properties, demonstrate significant difference along thea-axis andb-axis directions when exposed to four kinds of VOCs: acetone, methanol, ethanol, and IPA. Remarkably, the responses of ReS2were significantly magnified under ultraviolet (UV) illumination, particularly in the case of acetone, where the response amplified by 10-15 times and the detection limit decreasing from 70 to 4 ppm compared to the dark conditions. Exploiting the discernible variances in responses along thea-axis andb-axis under both UV and dark conditions, the data points of acetone, ethanol, methanol and IPA gases were clearly separated in the principal component space without any overlap through principal component analysis, indicating that the single ReS2FET has a high ability to distinguish various gas species. The exploration of anisotropic sensing materials and light excitation strategies can be applied to a broad range of sensing platforms based on two-dimensional materials for practical applications.

Fuzzy PID control of permanent magnet synchronous motor electric steering engine by improved beetle antennae search algorithm.

The accuracy of control in permanent magnet synchronous motor system significantly affects overall mechanical structure safety. To satisfy high-performance control for the position servo of the electric steering engine, this study selects a suitable vector control model for permanent magnet synchronous motor. Additionally, an enhanced beetle antennae search algorithm is designed and employed to optimize the fuzzy proportional-integral-derivative controller. The hybrid fuzzy proportional-integral-derivative controller is then implemented in the control model of the permanent magnet synchronous motor, resulting in the establishment of a novel control model for the electric steering engine driven by the permanent magnet synchronous motor. The test results showed that root-mean-square error of this control model was 0.03 mm and 0.02 mm respectively under the conditions of sinusoidal response, square wave response and step response, which was obviously shorter than all the selected control models. In addition, the standard deviation of the control model designed in this study accounted for less than 4% of root-mean-square error of electric steering engine position under the sinusoidal response condition, so the calculation stability was high. The research results show that the designed control model has a certain reference value for improving servo control performance of permanent magnet synchronous motor.

All-Dielectric Integrated Meta-Antenna Operating in 6G Terahertz Communication Window.

Efficient transceivers and antennas at terahertz frequencies are leading the development of 6G terahertz communication systems. The antenna design for high-resolution terahertz spatial sensing and communication remains challenging, while emergent metallic metasurface antennas can address this issue but often suffer from low efficiency and complex manufacturing. Here, an all-dielectric integrated meta-antenna operating in 6G terahertz communication window for high-efficiency beam focusing in the sub-wavelength scale is reported. With the antenna surface functionalized by metagrating arrays with asymmetric scattering patterns, the design and optimization methods are demonstrated with a physical size constraint. The highest manipulation and diffraction efficiencies achieve 84.1% and 48.1%. The commercially accessible fabrication method with low cost and easy to implement has been demonstrated for the meta-antenna by photocuring 3D printing. A filamentous focal spot is measured as 0.86λ with a long depth of focus of 25.3λ. Its application for integrated imaging and communication has been demonstrated. The proposed technical roadmap provides a general pathway for creating high-efficiency integrated meta-antennas with great potential in high-resolution 6G terahertz spatial sensing and communication applications.

Rapid and noninvasive cell assay by microfluidic-integrated intracavity evanescent field absorption in a fiber ring laser.

BACKGROUND: Highly sensitive and rapid detection of cell concentration and interfacial molecular events is of great value for biological, biomedical, and chemical research. Most traditional biosensors require large sample volumes and complicated functional modifications of the surface. It is of great significance to develop label-free biosensor platforms with minimal sample consumption for studying cell concentration changes and interfacial molecular events without labor-intensive procedures. RESULTS: Here, a fiber-optic biosensor based on intracavity evanescent field absorption sensing is designed for sensitive and label-free cell assays for the first time. The interaction between the cells and the evanescent field is enhanced by introducing microfluidic-integrated intracavity absorption in a fiber ring laser. This strategy extends the range of targeted analytes to include quantification of a large number of targets on a surface and improves the detection sensitivity of the fiber-optic biosensor. The level of sensing resolution could be improved from 10-4 RIU to 10-7 RIU using this strategy. The stem cells were studied over a wide concentration range (from 500 to 1.2 × 105 cells/ml) and were measured sequentially. By measuring the output power of the intracavity absorption sensing system, the cell concentration can be directly determined in a label-free manner. The results show that dozens of stem cells can be sensitively detected with a sample consumption of 72 µL. The response was fast (15 s) with a low temperature cross-sensitivity of 0.031 cells·ml-1/°C. SIGNIFICANCE: The proposed method suggests its capacity for true label-free and noninvasive cell assays with a low limit of detection and small sample consumption. This has the potential to be used as a universal tool for quantitative and qualitative characterization of various cells and other biochemical analytes.

A Novel Deep Convolutional Neural Network Combining Global Feature Extraction and Detailed Feature Extraction for Bearing Compound Fault Diagnosis.

This study researched the application of a convolutional neural network (CNN) to a bearing compound fault diagnosis. The proposed idea lies in the ability of CNN to automatically extract fault features from complex raw signals. In our approach, to extract more effective features from a raw signal, a novel deep convolutional neural network combining global feature extraction with detailed feature extraction (GDDCNN) is proposed. First, wide and small kernel sizes are separately adopted in shallow and deep convolutional layers to extract global and detailed features. Then, the modified activation layer with a concatenated rectified linear unit (CReLU) is added following the shallow convolution layer to improve the utilization of shallow global features of the network. Finally, to acquire more robust features, another strategy involving the GMP layer is utilized, which replaces the traditional fully connected layer. The performance of the obtained diagnosis was validated on two bearing datasets. The results show that the accuracy of the compound fault diagnosis is over 98%. Compared with three other CNN-based methods, the proposed model demonstrates better stability.

All-Dielectric Tunable Terahertz Metagrating for Diffraction Control.

Recently, tunable metagratings have attracted substantial attention in manipulating the diffraction of electromagnetic waves with considerable flexibility, but they are usually limited to inherent ohmic loss due to the metal layers. The all-dielectric schemes can address this issue, but its design and optimization remain challenging in the terahertz regime, especially in the 6G communication window. In this work, an all-dielectric tunable terahertz metagrating is demonstrated in theoretical and experimental investigations. The metagrating operating in the 6G communication window bends the electromagnetic waves beam into the T-1 diffraction order by optimizing the unit cell. In the experiments, more than 72.46% of the transmitted energy is concentrated in the desired diffraction order for p-polarized light and more than 66.60% for s-polarized light, which agrees well with the theoretical design. The tunability by angular deflection is reported in this all-dielectric metagrating. Then, based on the all-dielectric metagrating arrays, a metalens with numerical aperture of NA = 0.39 at 0.14 THz is demonstrated. The subwavelength scale focal spot is obtained as 2.0 mm × 2.0 mm with the focusing distance of 117.8 mm. Imaging capability of the metalens is performed utilizing the transmission imaging manner. The measured and anticipated results are satisfactorily congruous with one another, which could validate our design. This work paves the way toward designing highly efficient and tunable devices with potential applications in terahertz communications, sensors, and super-resolution imaging.

Artificial Intelligence-Assisted Terahertz Imaging for Rapid and Label-Free Identification of Efficient Light Formula in Laser Therapy.

Photodynamic therapy (PDT) is considered a promising noninvasive therapeutic strategy in biomedicine, especially by utilizing low-level laser therapy (LLLT) in visible and near-infrared spectra to trigger biological responses. The major challenge of PDT in applications is the complicated and time-consuming biological methodological measurements in identification of light formulas for different diseases. Here, we demonstrate a rapid and label-free identification method based on artificial intelligence (AI)-assisted terahertz imaging for efficient light formulas in LLLT of acute lung injury (ALI). The gray histogram of terahertz images is developed as the biophysical characteristics to identify the therapeutic effect. Label-free terahertz imaging is sequentially performed using rapid super-resolution imaging reconstruction and automatic identification algorithm based on a voting classifier. The results indicate that the therapeutic effect of LLLT with different light wavelengths and irradiation times for ALI can be identified using this method with a high accuracy of 91.22% in 33 s, which is more than 400 times faster than the biological methodology and more than 200 times faster than the scanning terahertz imaging technology. It may serve as a new tool for the development and application of PDT.

Design and Analysis of a 6-DOF Magnetic Suspension Platform with an Improved Permanent Magnetic Array.

For ultra-precision, large stroke, and high start/stop acceleration, a novel 6-DOF magnetic suspension platform with a novel structure of the permanent array is proposed. The structure and the working principle of the novel platform are introduced. An accurate model of the novel structure was established to calculate the magnetic density distribution for obtaining the parameters and performance of the magnetic suspension platform. The analytical model's results were verified by the finite element method. The driving force model of the magnetic suspension platform was established based on the Lorentz force. Twelve laser displacement sensors were applied to perceive the posture and vibration acceleration of the platform. The hardware information and the measurement models were introduced and established based on the layout. Finally, the Lorentz force characteristics of the proposed platform were investigated and compared with the conventional magnetic platform by the finite element analysis. The results show that the average magnetic flux density is 0.54T, the horizontal current stiffness along the X-axis is 63.1N/A, the current stiffness along the Y-axis is 61.6N/A, and the average output torque is 7.2 N*cm of the novel platform, larger than those of the conventional ones.

Numerical Demonstration of 800 Gbps WDM Silicon Photonic Transmitter with Sub-Decibel Surface-Normal Optical Interfaces.

We propose and numerically demonstrate an 800 Gbps silicon photonic transmitter with sub-decibel surface-normal optical interfaces. The silicon photonic transmitter is composed of eight silicon Mach-Zehnder optical modulators and an interleaved AMMI WDM device. This WDM device comprises two 1 × 4 angled MMI and a Mach-Zehnder interferometer (MZI) optical interleaver with an apodized bidirectional grating which has about -0.5 dB coupling loss. Both the Mach-Zehnder electro-optical modulators and MZI optical interleaver regard the bidirectional grating coupler as vertical optical coupler and 3-dB power splitter/combiner. By importing the S-parameter matrices of all the components which have been carefully designed in simulation software, the circuit-level model of the optical transmitter can be built up. On this basis, the static and dynamic performance characterization were carried out numerically. For NRZ modulation, the optical transmitter exhibits the overall optical loss of 4.86-6.72 dB for eight wavelength channels. For PAM4 modulation, the optical loss is about 0.5 dB larger than that of NRZ modulation, which varies between 5.38-7.27 dB. From the eye diagram test results, the WDM silicon photonic transmitter can achieve single channel data transmission at 100 Gb/s NRZ data or 50 GBaud/s PAM4 symbol rate with acceptable bit error rate.

Bidirectional grating based interleaved angled MMI for high-uniformity wavelength division (de)multiplexing and surface-normal fiber packaging.

We propose and experimentally demonstrate a vertical fiber interfacing interleaved angled multimode interference (MMI) coupler for wavelength-division multiplexing (WDM) applications. This four-channel WDM device comprises two 1×2 angled MMI couplers and a bidirectional grating-based Mach-Zehnder interferometer (MZI) structure. In the MZI optical interleaver, the uniform bidirectional grating functions as both the perfectly vertical grating coupler and the 3 dB power splitter. Benefitting from the flat-top coupling spectrum of the grating coupler, a high-uniformity wavelength-division (de)multiplexing can be achieved with a simulated insertion loss of 3.15-3.36 dB (the nonuniformity of 0.22 dB). The angled MMIs (AMMIs) are designed and optimized using the eigenmode expansion method. For wavelength matching between the MZI and AMMIs, the circuit simulation model of the interleaved AMMI is built by importing the S-parameter matrices of all the optical components extracted from the physical level simulations. The device was fabricated using standard CMOS technology and all the features were patterned with the 193-nm deep-UV lithography. Experimental results obtained without thermal tuning are in good agreement with the simulation results. The device exhibits an insertion loss of 4.5-4.65 dB (nonuniformity of 0.15 dB), channel spacing of 10 nm, and cross talk of -(21.62-26)dB.

High-Performance Flexible Ultraviolet Photodetectors Based on AZO/ZnO/PVK/PEDOT:PSS Heterostructures Integrated on Human Hair.

Flexible optoelectronics is an emerging research field that has attracted a great deal of interest in recent years due to the special functions and potential applications of these devices in flexible image sensors, optical computing, energy conversion devices, the Internet of Things, and other technologies. Here, we examine the high-performance ultraviolet (UV) photodetectors using AZO/ZnO nanorods/PVK/PEDOT:PSS heterostructures integrated on human hair. Due to the precise interfacial energy-level alignment among all layers and superior mechanical characteristics of human hair, the as-obtained photodetector shows a fast response time, high photoresponsivity, and excellent flexibility. According to integrate 7 heterostructures as 7 display pixels, the flexible UV-image sensor has superior device performance and outstanding flexibility and can produce vivid and accurate images of Arabic numerals from 0 to 9. Different combinations of the two heterostructures can also be used to achieve flexible photon-triggered logic functions, including AND, OR, and NAND gates. Our findings indicate the possibility of using human hair as a fiber-shaped flexible substrate and will allow the use of hair-based hierarchical heterostructures as building blocks to create exciting opportunities for next-generation high-performance, multifunctional, low-cost, and flexible optoelectronic devices.

Multi-wavelength tailoring of a ZnGa2O4 nanosheet phosphor via defect engineering.

The multi-wavelength luminescence tailoring of an individual phosphor free of external dopants is of great interest and technologically important for practical applications. Using ZnGa2O4 nanosheets as a target phosphor, we demonstrate how to artificially control the luminescence wavelength centers and their emission intensities to simultaneously emit ultraviolet/blue, green and red light via a feasible defect engineering strategy. Simple high-temperature annealing of hydrothermally synthesized ZnGa2O4 nanosheets leads to the effective tunability of their emission process to present multi-wavelength luminescence due to the structural distortion and the formation of oxygen vacancies. Controlling the annealing temperature and time can further precisely modulate the wavelengths and their corresponding intensities. It is speculated that the migration of Ga into the [GaO4] tetrahedron and the O vacancy are responsible for the multi-wavelength luminescence of the ZnGa2O4 nanosheet phosphor. Finally, the tentative multi-wavelength luminescence behavior of the ZnGa2O4 nanosheet phosphor via defect engineering is discussed based on a series of evidenced experimental observations of XRD, XPS, HRTEM and CL.

Template Approach to Crystalline GaN Nanosheets.

Crystalline GaN nanosheets hold great challenge in growth and promising application in optoelectronic nanodevices. In this work, we reported an accessible template approach toward the rational synthesis of GaN nanosheets through the nitridation of metastable γ-Ga2O3 nanosheets synthesized from a hydrothermal reaction. The cubic γ-Ga2O3 nanosheets with smooth surface and decent crystallinity can be directly converted into hexagonal GaN nanosheets with similar morphology framework and comparable crystal quality in NH3 at 850 °C. UV-vis spectrum measurement reveals that the GaN nanosheets show a band gap of 3.30 eV with strong visible absorption in the range of 370-500 nm. The template synthetic strategy proposed in this work will open up more opportunities for the achievement of a variety of sheetlike nanostructures that can not be obtained through conventional routines and will undoubtedly further promote the fundamental research of newly emerging sheetlike nanostructures and nanotechnology.

[Research and Design of a Blue and Green Light Emitting Diode Phototherapy System Based on Fly Eye Lens for Jaundice].

Light emitting diode(LED)can be used in the treatment of jaundice.Blue and green LED irradiation affected with the newborn is currently considered the most effective treatment of the jaundice in the world.A jaundice phototherapy system with blue and green LED as light source utilizing fly eye lens array was built to achieve uniform illumination in the present study.AMC7150 chip was used to build the constant current drive module,and AT89C52 MCU and LCD12864 LCD screen were used to build the human-computer interaction module.Based on national particular phototherapy equipment requirements(YY0669-2008)for the safety,we designed and implemented a phototherapy system which spot area was 250mm×500mm,blue light irradiance reached 2mW/cm2,green light irradiance reached 1.5mW/cm2,and the uniformity of light was over 90%.Compared with the traditional system,the new one designed in this study has better therapeutic effect,higher biological safety,easier to achieve man-machine interaction,and more economical and convenient.

Localized surface waves at the interface between linear dielectric and biased centrosymmetric photorefractive crystals.

We study localized surface waves at the interface between linear dielectric and biased centrosymmetric photorefractive (CP) crystals. If the propagation constant b is fixed, the energy of localized surface waves increases with the order of localized surface waves. For low b values, the considerable part of the energy of localized surface waves is concentrated in the linear dielectric and decreases with an increase in b. For high b values, the part of the energy of localized surface waves concentrated in the nonlinear CP crystals is always higher than that in the linear dielectric and increases with b. The stability properties of these localized surface waves are also discussed in detail.