Publications

Significant Enhancement of Triboelectric Charge Density by Fluorinated Surface Modification in Nanoscale for Converting Mechanical Energy

Excellent triboelectric and mechanical properties are achieved on the same material for the first time by developing an effective, general, straightforward, and area‐scalable approach to surface modification of a polyethylene terephthalate (PET) film via inductive‐coupled plasma etching. The modification enables gigantic enhancement of triboelectric charge density on the PET surface. Based on the modified PET as a contact material, a triboelectric nanogenerator (TENG) exhibits significantly promoted electric output compared to the one without the modification. The obtained electric output is even superior to a TENG made of conventional polytetrafluoroethylene that is known for its strongest ability of being charged by triboelectrification among all engineering plastics. Detailed characterizations reveal that the enhancement of triboelectric charge density on the PET is attributed to both chemical modification of fluorination and physical modification of roughened morphology in nanoscale. Therefore, this work proposes a new route to obtaining high‐performance TENGs by manipulating and modifying surface properties of materials.

Contaction of Atoms for Outstanding Dielectric Characteristics in Kx-Passivated Polymer Dielectrics

High dielectric characteristics polymer dielectrics are crucial for high-power, high-integration, and high-energy storage density electrical devices and film capacitors. However, polymer dielectrics accumulate much charge during operation, causing local electric field distortion and flashover or breakdown. The deep-level defect state (electron/hole accumulation center) is a fundamental factor affecting dielectric strength. Unfortunately, related research, especially on passivating deep-level defects in polymer dielectrics, is minimal. In this paper, based on experiments and first-principles calculations, it is found that KX (X=F, Cl, Br, I) effectively passivates deep-level defect states in polymer dielectrics. Further analysis of the physical passivation mechanism reveals that the deep-level defect cation passivation principle is the cation dipole effect on polymers. The principle of anion passivation of deep-level defects by suspending anions and cations is the key to producing more stable C covalent bonds. This stable covalent bond transfers the local charge from the C with the lone electron pair that originally contains the hanging bond. Therefore, some transfer occurs and the anion implements effective passivation. This paper addresses the design of high-performance polymer dielectrics, providing a reference for experimental and theoretical analyses.

Diagnostic system based on support-vector machines for board-level functional diagnosis

Fault diagnosis is critical for improving product yield and reducing manufacturing cost. However, it is very challenging to identify the root cause of failures on a complex circuit board. Ambiguous diagnosis results lead to long debug times and even wrong repair actions, which significantly increases the repair cost. We propose an automatic diagnostic system using support vector machines (SVMs). The proposed system acquires debug knowledge from empirical data; this strategy avoids the difficulties involved in knowledge acquisition in traditional fault diagnosis methods. SVMs provide an optimal separating hyperplane in classification. The optimal solution and generalization ability of SVMs lead to higher diagnostic accuracy, compared to the classical learning approaches such as artificial neural networks (ANNs). An industrial board is used to validate the effectiveness of the proposed system. Extensive simulation results demonstrate that the SVMs-based diagnostic system provides quantifiable improvement over current diagnostic software and an ANN-based diagnostic system.

Dynamic regulating of single-mode lasing in ZnO microcavity by piezoelectric effect

Research on Flower Image Classification Based on Transfer Learning

Due to the high similarity between flowers, it is difficult to identify them if they do not have the corresponding biological knowledge when classifying varieties manually. Given the above problems, to improve the accuracy and efficiency of flower classification, this paper proposes a migration parameter pre-training and fine-tuning VGG16 model based on the ImageNet data set to solve this problem. In this paper, the grid coverage enhancement method enhances the flower classification data set to expand the training sample data. The model uses the migration learning pre-training and fine-tuning method to improve network stability and accelerate network convergence. The results of comparative experiments show that the performance of the improved model has been significantly improved, and the result is better on the flower image data set, which has specific practical value.

Clinical experiences in the management of critically ill patients with COVID-19 in a designated children’s hospital in China

Flexo-photocatalysis in centrosymmetric semiconductors

A paradigm shift fully self-powered long-distance wireless sensing solution enabled by discharge-induced displacement current

The rapid development of the Internet of Things depends on wireless devices and their network. Traditional wireless sensing and transmission technology still requires multiple modules for sensing, signal modulation, transmission, and power, making the whole system bulky, rigid, and costly. Here, we proposed a paradigm shift wireless sensing solution based on the breakdown discharge–induced displacement current. Through that, we can combine the abovementioned functional modules in a single unit of self-powered wireless sensing e-sticker (SWISE), which features a small size (down to 9 mm by 9 mm) and long effective transmission distance (>30 m) when compared to existing wireless sensing technologies. Furthermore, SWISEs have functions of multipoint motion sensing and gas detection in fully self-powered manner. This work proposes a solution for flexible self-powered wireless sensing platforms, which shows great potential for implantable and wearable electronics, robotics, health care, infrastructure monitoring, human-machine interface, virtual reality, etc.

Numerical Investigation on Wide-Chord Fan Blade Forced Response due to Vortex Ingestion

When a turbofan engine is taxing or taking-off, a vortex can form between ground surface and the intake. As the diameters of engines increase, intakes are closer to the ground and as a result the possibility of vortex ingestion is increasing. The vortex starts from the ground surface and enters the inlet at high rotating speed. It is likely to draw in hard material or dust from the ground, which leads to blade erosion or impact damage. This is harmful to the engine durability and safety. Besides the vortex, inlet flow separation could induce high level of blade vibration, or aerodynamic instability, such as rotating stall. Cross wind may also lead to both vortex and flow distortion, which is more challenging for engine stability. Therefore, vibration characteristics and forced response under vortex ingestion should be evaluated to ensure the stability and safety of the engine in design phase. This paper presents a computational study of the forced response of a wide-chord fan blade under vortex ingestion. A finite element model was built, and modal analysis was conducted to characterize the vibrating characteristics of the fan blade with a corresponding Campbell diagram. Transient simulations of vortex passing over the fan blade were conducted with and without the blade pre-vibration at the natural frequency of the first bending mode. The forced response level was evaluated under various conditions, including different hitting time and increasing intensity of vortex. Results showed that the ingested vortex is able to amplify the displacement and vibratory response to a significant level of 18% at most. Linear relation between vortex intensity and blade response was found. The results give a comprehensive prediction of forced response for a better blade design against vortex ingestion.

Microemulsions

Identification of potent, noncovalent fatty acid amide hydrolase (FAAH) inhibitors

Biodegradable Piezo-triboelectric Charge Nanogenerator Patch for Cartilage Regeneration

Cartilage degradation is a hallmark of osteoarthritis. Restoring the natural bioelectric environment of osteoarthritic tissue could offer a promising treatment strategy through physical modulation. We report a microsized, biodegradable implantable patch that utilizes a piezoelectric effect-enhanced triboelectric charge generator (PTEG) to promote cartilage regeneration and osteoarthritis healing. Featuring a triboelectric architecture with macroscopic pyramids and microscopic porosities, the PTEG patch produces a charge density of 242 μC m^-2 in vitro and 84 μC m^-2 in vivo, approximately 2 orders of magnitude higher than that of the state-of-the-art implantable charge generators. Additionally, the PTEG patch demonstrates excellent biocompatibility and tunable degradability. In vitro experiments show that the PTEG significantly promotes bone marrow stem cell migration, Ca²⁺ influx, and chondrogenic gene expression. In an osteoarthritis rat model, PTEG implantation was shown to reduce osteophyte formation and enhance cartilage regeneration significantly.

Topographically-Designed Triboelectric Nanogenerator via Block Copolymer Self-Assembly

Herein, we report a facile and robust route to nanoscale tunable triboelectric energy harvesters realized by the formation of highly functional and controllable nanostructures via block copolymer (BCP) self-assembly. Our strategy is based on the incorporation of various silica nanostructures derived from the self-assembly of BCPs to enhance the characteristics of triboelectric nanogenerators (TENGs) by modulating the contact-surface area and the frictional force. Our simulation data also confirm that the nanoarchitectured morphologies are effective for triboelectric generation.

MBE growth and characterization of SrGa[sub 2]S[sub 4]:Ce blue phosphor for thin-film electroluminescence

Abstract— In this paper, we report further investigations of the MBE growth and characterization of cerium‐doped strontium thiogallate (SrGa 2 S 4 : Ce). Using Sr, Ga 2 S 3 , and CeCl 3 as source materials the optimum growth conditions for single‐phase polycrystalline SrGa 2 S 4 film were found to be substrate temperatures of 550–560°C and Ga 2 S 3 /Sr beam equivalent pressure (BEP) ratios of 50–60. CeCl 3 /Sr flux (molecules cm −2 s −1 ) ratios of 0.01–0.1 were studied, and the optimum Ce doping concentration has been found to be about 3 at.%. Characterization of the structural, electrical, and optical properties by XRD, TEM, EDS, SIMS, and PL will be presented.

Real-time traffic sign detection and recognition for intelligent vehicle

This paper proposes a stable system for the real time traffic sign detection and recognition, especially for the geometric distortions of traffic sign. In detection phase, color-based segmentation is applied to remove the background, then in the shape analysis subsection, the Fast Fourier transform (FFT) is used to solve the rotation and scaling problems of the traffic sign. A template database which includes the common projection distortion shapes was established to overcome the effects of the projection distortions. For object occlusions, using the method of contours convex hull to weaken the influence of occlusions. Hence, we can obtain the candidate regions of interest (ROIs). In recognition phase, the Histogram of oriented gradient (HOG) features are extracted from normalized ROIs, we propose a method which uses linear Support Vector Machine (SVM) classifier for classification. The system is verified on our intelligent vehicle named as Intelligent Pioneer. This algorithm shows good robust against scaling, occlusion, rotation and projection distortion while the accuracy of recognition is more than 93%.

Textile Triboelectric Nanogenerators Simultaneously Harvesting Multiple “High-Entropy” Kinetic Energies

Distributed renewable kinetic energies are ubiquitous but with irregular amplitudes and frequencies, which, as one category of "high-entropy" energies, are crucial for next-generation self-powered electronics. Herein, we present a flexible waterproof dual-mode textile triboelectric nanogenerator (TENG), which can simultaneously scavenge multiple "high-entropy" kinetic energies, including human motions, raindrops, and winds. A freestanding-mode textile TENG (F-TENG) and a contact-separation-mode textile TENG (CS-TENG) are integrated together. The structure parameters of the textile TENG are optimized to improve the output performances. The raindrop can generate a voltage of up to ∼4.3 V and a current of about ∼6 μA, while human motion can generate a voltage of over 120 V and a peak power density of ∼500 mW m–2. The scavenged electrical energies can be stored in capacitors for powering small electronics. Therefore, we demonstrated a facile preparation of a TENG-based energy textile that is highly promising for kinetic energy harvesting and self-powered electronics.

Self‐Generated Displacement Current of Triboelectric Nanogenerator for Cancer Therapy: Theory and Application (Adv. Mater. Technol. 2/2024)

Triboelectric Nanogenerators Self-generated dynamic electric field or displacement current of triboelectric nanogenerators (TENGs) can operate from micrometers to centimeters, which offers a key technology for TENG based therapy system for precision medicine on both tissues and cells. TENGs have low-current and high-voltage properties, which reduce damage to normal tissues, and kill rapidly dividing cancer cells. More detail can be found in article 2301225 by Jinyi Lang, Yan Zhang, Zhong Lin Wang, and co-workers.

Ultrafine Capillary‐Tube Triboelectric Nanogenerator as Active Sensor for Microliquid Biological and Chemical Sensing

Abstract A practical, highly flexible capillary‐tube triboelectric nanogenerator (ct‐TENG) is reported as a microfluidic sensor. The ct‐TENG is composed of an ultrafine tubular sandwich structure of polytetrafluoroethylene capillary tube, double helix aluminum foil, and silicon rubber hermetic tube. For the first time, microliter sampling (sampling volume, 0.5 µL), nondestructive and highly flexible, is achieved simultaneously for a microliquid sensing device. The self‐powered ct‐TENG is capable of outputting selectable electrical signals (1.1 V, 10 nA, 0.9 nC) used for sensing a volume of 0.5 µL microliquid due to Maxwell's displacement current generated with energy converted from microliquid flow. It also achieves both total aerobic count monitoring and electrical conductivity (κ) detection. Moreover, the ct‐TENG is ultrafine/highly flexible structure and enables its application as a microliter magnitude active sensor for qualitative/quantitative detection. This work provides new opportunities for multifunctional sensing and potential applications in microliquid biological and chemical monitoring/detection technology.