Recent developments in deep-ultraviolet sterilization of human respiratory RNA viruses

Deep-ultraviolet (DUV) sterilization technology using DUV-LEDs has attracted considerable attention owing to its portability, eco-friendliness, high potency, and broad-spectrum sterilization. This study compiles the developments of recent DUV sterilization research. Recent works have investigated DUV sterilization from the perspective of device improvement and principle investigation: one employed a novel epitaxial structure to optimize the performance and fabrication cost of DUV-LEDs and realized potent virus disinfection effects for various respiratory RNA viruses, and another work explained the disinfection phenomenon of SARS-CoV-2 and its variants (Delta and Omicron) in a cryogenic environment. These studies have contributed significantly to the development of DUV sterilization

Full-Color Micro-LED Devices Based on Quantum Dots

Quantum dots (QDs) show remarkable optical and electrical characteristics. They offer the advantage of combining micro-LEDs (μLEDs) for full-color display devices due to their exceptional features. In addition, μLED used in conjunction with QDs as color-conversion layers also provide efficient white LEDs for high-speed visible light communication (VLC). In this article, we comprehensively review recent progress in QD-based μLED devices. It includes the research status of various QDs and white LEDs based on QDs’ color conversion layers. The fabrication of QD-based high-resolution full-color μLEDs is also discussed. Including charge-assisted layer-by-layer (LbL), aerosol jet printing, and super inkjet printing methods to fabricate QD-based μLEDs. The use of quantum dot photoresist in combination with semipolar μLEDs is also described. Finally, we discuss the research of QD-based μLEDs for visible light communication

Applications of lasers: A promising route toward low-cost fabrication of high-efficiency full-color micro-LED displays

Micro-light-emitting diodes (micro-LEDs) with outstanding performance are promising candidates for next-generation displays. To achieve the application of high-resolution displays such as meta-displays, virtual reality, and wearable electronics, the size of LEDs must be reduced to the micro-scale. Thus, traditional technology cannot meet the demand during the processing of micro-LEDs. Recently, lasers with short-duration pulses have attracted attention because of their unique advantages during micro-LED processing such as noncontact processing, adjustable energy and speed of the laser beam, no cutting force acting on the devices, high efficiency, and low cost. Herein, we review the techniques and principles of laser-based technologies for micro-LED displays, including chip dicing, geometry shaping, annealing, laser-assisted bonding, laser lift-off, defect detection, laser repair, mass transfer, and optimization of quantum dot color conversion films. Moreover, the future prospects and challenges of laser-based techniques for micro-LED displays are discussed

A Building Segmentation Network Based on Improved Spatial Pyramid in Remote Sensing Images

Building segmentation is widely used in urban planning, disaster prevention, human flow monitoring and environmental monitoring. However, due to the complex landscapes and highdensity settlements, automatically characterizing building in the urban village or cities using remote sensing images is very challenging. Inspired by the rencent deep learning methods, this paper proposed a novel end-to-end building segmentation network for segmenting buildings from remote sensing images. The network includes two branches: one branch uses Widely Adaptive Spatial Pyramid (WASP) structure to extract multi-scale features, and the other branch uses a deep residual network combined with a sub-pixel up-sampling structure to enhance the detail of building boundaries. We compared our proposed method with three state-of-the-art networks: DeepLabv3+, ENet, ESPNet. Experiments were performed using the publicly available Inria Aerial Image Labelling dataset (Inria aerial dataset) and the Satellite dataset II(East Asia). The results showed that our method outperformed the other networks in the experiments, with Pixel Accuracy reaching 0.8421 and 0.8738, respectively and with mIoU reaching 0.9034 and 0.8936 respectively. Compared with the basic network, it has increased by about 25% or more. It can not only extract building footprints, but also especially small building objects

A Novel Liquid Packaging Structure of Deep-Ultraviolet Light-Emitting Diodes to Enhance the Light-Extraction Efficiency

To realize high-efficiency, AlGaN-based, deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency and reducing thermal resistance is very crucial. We proposed a liquid packaging structure that could enhance optical power by 27.2% and 70.7% for flat type and lens type 281-nm DUV-LEDs, respectively. A significant improvement effect at different wavelengths, such as 268 nm and 310 nm, was also observed. Furthermore, using the liquid packaging structure, the thermal resistance was reduced by 30.3% compared to the conventional structure. Finally, the reliability of liquid packaging DUV-LEDs was tested. The light output maintenance of liquid packaging DUV-LEDs was compared to the conventional structure

Investigation on Key Parameters in the Fabrication of Stamps for Transfer Printing of Micro Devices

For the past few years, the transfer printing method has been developed and has secured numerous advantages. Here, via both experiments and analyses, we have focused on identifying key parameters and optimizing their values in the fabrication process of stamps for transfer-printing micro-devices. Specifically, the elastic modulus of posts is measured using the atomic force microscope and the Derjaguin, Muller, and Toporov model. Based on mold morphologies data, we subsequently explore the law of photoresist development under different design widths as well as development time, establish mathematical models, and offer relevant explanations for the formation of various developmental topographies. Furthermore, the relationship between the elastic modulus and these stamp-fabrication parameters has also been analyzed and confirmed. Hopefully, the proposed work can provide the guidance for fabricating reliable stamps in the future

Multi-Azimuth Failure Mechanisms in Phosphor-Coated White LEDs by Current Aging Stresses

We have experimentally analyzed multi-azimuth degradation mechanisms that govern failures of commercially-available high-power (1 Watt) phosphor-coated white (hppc-W) light-emitting diodes (LEDs) covered with peanut-shaped lenses under three current-stress aging (CSA) conditions. Comprehensive analyses focus on photometric, chromatic, electrical, thermal and packaging characteristics. At the packaging level, (a) the decrease of the phosphor-conversion efficiency; (b) the yellow-browning of the optical lens; and (c) the darkening of the silver-coated reflective layer deposited with extraneous chemical elements (e.g., C, O, Si, Mg, and Cu, respectively) contribute collectively to the integral degradation of the optical power. By contrast, Ohmic contacts, thermal properties, and angles of maximum intensity remain unchanged after 3840 h aging in three cases. Particularly at the chip level, the formation of point defects increases the number of non-radiative recombination centers, and thus decreases the optical power during aging stages. Nevertheless, in view of the change of the ideality factor, the Mg dopant activation and the annealing effect facilitate the increase of the optical power in two specific aging stages (192 h~384 h and 768 h~1536 h). This work offers a systematic guidance for the development of reliable LED-based light sources in general-lighting areas