LED Array Research Articles

Quadrant darkfield (QDF) for label-free imaging of intracellular puncta.

Measuring changes in cellular structure and organelles is crucial for understanding disease progression and cellular responses to treatments. A label-free imaging method can aid in advancing biomedical research and therapeutic strategies. This study introduces a computational darkfield imaging approach named quadrant darkfield (QDF) to separate smaller cellular features from large structures, enabling label-free imaging of cell organelles and structures in living cells. Using a programmable LED array as illumination source, we vary the direction of illumination to encode additional information about the feature size within cells. This is possible due to the varying level of directional scattering produced by features based on their sizes relative to the wavelength of light used. QDF successfully resolved small cellular features without interference from larger structures. QDF signal is more consistent during cell shape changes than traditional darkfield. QDF signals correlate with flow cytometry side scatter measurements, effectively differentiating cells by organelle content. QDF imaging enhances the study of subcellular structures in living cells, offering improved quantification of organelle content compared to darkfield without labels. This method can be simultaneously performed with other techniques such as quantitative phase imaging to generate a multidimensional picture of living cells in real-time.

Evaluation of Light-Induced Electroluminescence in Photovoltaic Field Applications

We present a performance analysis of the new measurement method Light-Induced Electroluminescence (LIEL) in a PV system. The LIEL method is applied to photovoltaic (PV) modules consisting of two PV module halves which are internally connected in parallel. Today’s main stream half-cell modules are constructed this way. To measure the electroluminescence of one half of the module, the other half is illuminated by an LED array. Our LIEL prototype system is a hood-based setup. It is equipped on one half with a LED array that is separated by a wall from the other half. This other half is observed by an InGaAs camera. We measure the impact of a LIEL hood misalignment to the electroluminescence intensity, the influence of the PV generator working point to the electroluminescence intensity and determine the measurement speed under realistic conditions. We show that the experimentally realized LIEL hood alignment to the PV modules is in 97.7% of the cases sufficient for acquiring high quality EL images. The LIEL system work with a switched off and on inverter. Under inverter on working condition the luminescence intensity is a function of the intensity of the sun. The effect of hood alignment and sun intensity on the luminescence intensity is successfully reproduced by an analogue electronic circuit simulation using LT Spice. The maximum measuring speed of a full module is in this study 12 s including the time for movement and alignment of the measurement hood from PV module to PV module

A non-contact solid particle moisture sensor based on near-infrared spectroscopy technology

The detection of moisture content in solid particles has important applications in fields such as biological research, coal mine production, and medicine. This article develops a non-contact solid particle moisture sensor (NcSPMS). NcSPMS uses the multi-light source detection method based on the principle of diffuse reflection absorption to detect the moisture content of solid particles with different particle sizes, distributions and colors. Firstly, the stacked LED light source structure (SLED-LSS) was designed to achieve illumination of LED light source for measurement (M-LED) and the LED light source for reference (R-LED) at the same position and exit angle, eliminating the influence of irregular particle size and distribution on diffuse reflected light intensity. Secondly, the stacked LED array light source structure (SLEDA-LSS) was designed to improve the detection light intensity and enable NcSPMS to detect the moisture content of solid particles of different colors. Thirdly, modulated light technology is used for the transmission of moisture content information. Two modulation frequencies were set to modulate the measurement light source and reference light source, and different intensities of square wave currents were determined to drive the M-LED and R-LED to improve detection accuracy. Fourthly, the FFT-KF data processing method was designed to effectively extract the information of diffuse reflection measurement light intensity. Finally, the function expression of moisture content was obtained through cubic fitting, and the detection of moisture content by NcSPMS was achieved. In order to verify the effectiveness of NcSPMS, the NcSPMS control system was designed. The experimental results show that compared with SLED-LSS, SLEDA-LSS improves measurement accuracy; the different current pairs driving M-LED and R-LED affect the measurement accuracy of NcSPMS; NcSPMS can detect the moisture content of white, yellow, green, red, and black sand particles, with the detection range of 0.10–11.00 %. The relative uncertainty obtained by applying NcSPMS to the detection of nickel ore particles is 4.37 %.

Facile printing of liquid–metal-based stretchable conductor using EGaIn/Ga2O3 composite

Printing gallium-based liquid metals (LMs) poses a significant challenge due to their high surface tension. In this work, we introduce a printable LM-based conductor using an EGaIn/Ga2O3 composite. This composite is achieved through a simple mixing process and is suitable for scalable stencil printing. The blend ratio of EGaIn/Ga2O3 is optimized to create LM pastes with an excellent balance of printability and electromechanical performance. Using these developed LM pastes, we successfully demonstrate a stretchable strain sensor with a gauge factor of 2 for monitoring human hand gestures. Additionally, we showcase a stretchable LED array deformable for up to 100% strain.

With Blue Light against Biofilms: Berberine as Natural Photosensitizer for Photodynamic Inactivation of Human Pathogens

Evolving antibiotic resistance of bacteria is a prevailing global challenge in health care and requires the development of safe and efficient alternatives to classic antibiotics. Photodynamic Inactivation (PDI) has proven to be a promising alternative for treatment of a broad range of microorganisms. Photodynamic Inactivation uses photoactive molecules that generate reactive oxygen species (ROS) upon illumination and in the presence of oxygen, which immediately kill pathogenic target organisms. Relevant photoactive properties are provided by berberine. Originally extracted from Barberry (Berberis vulgaris), it is a natural compound widely used in Traditional Chinese Medicine for its antimicrobial and anti-inflammatory effects. With this study, we demonstrated the potential of berberine chloride hydrate (Ber) as a photosensitizer for PDI of important human pathogens, Gram(+) Staphylococcus capitis subsp. capitis, Gram(+) Staphylococcus aureus, and Gram(−) Escherichia coli. In vitro experiments on planktonic and biofilm cultures were conducted focusing on Ber activated with visible light in the blue wavelength range. The number of planktonic S. capitis cells was reduced by 7 log10 steps using 100 µM Ber (5 min incubation, illumination with 435 nm LED array, radiant exposure 25 J/cm2). For an antibacterial effect of 4 log10 steps, static S. capitis biofilms required 1 mM Ber, a drug-to-light interval of 60 min, and illumination with 100 J/cm2. Almost all planktonic cells of Staphylococcus aureus could be photokilled using 100 µM Ber (drug-to-light interval of 30 min, radiant exposure 25 J/cm2). Biofilms of S. aureus could be phototreated (3 log10 steps inactivation) when using 1 mM Ber incubated for 5 min and photoactivated with 100 J/cm2. The study is highlighted by the proof that PDI treatment using Ber showed an antibacterial effect on Gram(−) E. coli. Planktonic cells could be reduced by 3 log10 steps with 100 µM Ber (5 min incubation, 435 nm, 25 J/cm2). With 5 mM ethylenediamine tetraacetic acid disodium salt dihydrate (Na2EDTA) or 1.2% polyaspartic acid (PASA) in addition, a relative inactivation of 4 log10 steps and 7 log10 steps, respectively, was detectable. Furthermore, we showed that an antibacterial effect of 3.4 log10 towards E. coli biofilms was given when using 1 mM Ber (5 min incubation, 435 nm, 100 J/cm2). These results underscore the significance of PDI-treatment with Ber as a natural compound in combination with blue light as valuable antimicrobial application.

Scanning Lagrangian Particle Tracking To Measure 3D Large Scale Aerodynamics Of Quadcopter Flight

We present large-scale time-resolved and volumetric measurements of the flow surrounding a quadcopter drone. Cases with hovering flight, forward flight - with and without ground-effect - as well as lift-off scenarios have been realized. Five high-speed cameras were used to capture images of hundreds of thousands heliumfilled soap bubbles being illuminated by pulsed LED arrays. The arrays were operated in a dual-scanning mode, where the front and the back part of the volume are illuminated intermittently, each with a frequency of 3 kHz. The cameras were recording at 6 kHz, thereby capturing both sub-time-series in a single measurement run. Compared to a full illumination of the volume, we can either reduce the number of particles imaged on the cameras given a fixed tracer concentration - facilitating the reconstruction - or operate at a higher tracer concentration while keeping the number of imaged particles fixed. The dual time-series were evaluated by Lagrangian Particle Tracking, using the Shake-The-Box method, yielding dense fields of particle tracks. For the current results, the time series for both sub-volumes were evaluated independently. For the final contribution, an integrated evaluation scheme, alternatingly operating on both time-series is foreseen. After the tracking step, flow structures were identified using the data assimilation method FlowFit. The temporally and spatially highly resolved results document the strong interaction of the wakes induced by several rotors, as well as the interaction of wing tip vortices stemming from a single rotor. Brown-out effects are documented in forward flight. Averaged results of hovering flight enable an evaluation of the azimuthal distribution of the downwash- and outwash-velocities resulting from the geometric layout of the four rotors. By having highly resolved data encompassing the whole flight vehicle, the forces conveyed by the drone to the liquid can be determined via surface- or volume-integration.

Validating Volumetric Measurements Using Helium-Filled Soap Bubbles in a Turbulent Boundary Layer And Wake Of An Axisymmetric Body Of Revolution

This study focuses on the validation of a volumetric measurement technique to characterize the turbulent boundary layers (TBL) and wake of a slender axisymmetric body. Specifically, Lagrangian Particle Tracking (LPT) was employed to analyse a TBL subjected to an adverse pressure gradient (APG) and transverse curvature at the tail of an axisymmetric body, with a Reynolds number based on model length of 3.95×10 6 . For the LPT method, a seeding rake with 100 nozzles was used to disperse helium-filled soap bubbles (HFSB), which served as tracers. These tracers were illuminated by high-powered LED arrays, allowing their motion to be captured by three high-speed cameras at acquisition rates up to 20 kHz. A key aspect of this research was using shadowgraphy to measure the diameter of the bubbles exiting the nozzles and obtaining their statistical variations across the various nozzles in the seeding rake. The study identified that the diameter of bubbles averaged 0.45 mm, indicating a state of near-neutral buoyancy. The LPT results were then obtained using the shake-the-box (STB) tracking alogirthm, while ensemble bin-averaging of the scattered particle tracks was used to obtain turbulence statistics on a regular grid. To validate the LPT results, comparisons were made with time-resolved 2D Particle Image Velocimetry (TR-PIV) and highly resolved hot-wire anemometry. This comparative analysis revealed good agreement of the mean profiles across the methodologies, highlighting the robustness and accuracy of the LPT technique. While the turbulence levels in the outer layer were well captured by the LPT, some discrepancies were observed near the wall in both PIV and LPT data, indicating limitations in capturing small-scale phenomena. The implications of these findings, particularly in understanding the complex 3D flow effects of such TBLs and the resulting wake flow field are discussed.

Sensitive and High-Throughput Time-Resolved Luminescence Detection of Tetracycline in Milk for Eliminating Background Fluorescence on a Miniaturized Apparatus.

Fluorescence detection has always suffered from high background fluorescence from real samples such as milk. Therefore, cumbersome pretreatments of samples were necessary to remove the fluorescent substances but led to long processing times and low efficiency. Time-resolved luminescence detection is a powerful technique for eliminating short-lived background fluorescence without additional pretreatments. However, the related instruments are usually equipped with high-speed excitation sources and detectors, which are always bulky and expensive. Herein, we developed a low-cost and miniaturized imaging system for high-throughput time-gated luminescence detection. An UV LED array was used to excite multiple samples, the luminescence of which could be detected by a smartphone simultaneously. An analog circuit was designed to synchronize the LED to the mechanical chopper to eliminate the background signals resulting from scattering and short-lived autofluorescence. Compared to other synchronous circuits based on FPGAs and microcontrollers, this analog circuit required no programming and memory. For the first time, high-throughput time-resolved luminescence detection of tetracycline in milk without any separation or enrichment was achieved by utilizing a smartphone as a camera, and the scattered signals and the background fluorescence were eliminated efficiently. The limit of detection reached as low as 53 nM (∼0.024 ppm), lower than the residue limit set by the European Union. This high-throughput time-gated luminescence detection method can be used for quantitative analysis of many real samples with high background fluorescence.

Strained Germanium Microbridge LED Array Using Elliptical Windows Etching

Strained Germanium Microbridge LED Array Using Elliptical Windows Etching

Design of a Device Based on an LED Matrix for Water Sterilization

The scarcity of potable water emphasizes the urgent need to develop and implement more sustainable treatment technologies, considering both energy consumption and environmental impact. These technologies require effective disinfection systems that avoid the use of chemicals. Innovations in this area, utilizing UV-LED technology, can significantly improve efficiency, reduce costs, and mitigate environmental impacts. This study aimed to evaluate the antimicrobial properties of various encapsulated UV light-emitting diodes (LEDs) to identify the most suitable candidate for constructing an LED array capable of disinfecting large volumes of water. Different devices from various manufacturers, with differing costs and wavelengths, were examined, leading to the selection of the optimal candidate (LED 2) based on its antimicrobial effectiveness and cost-effectiveness. The impact of parameters such as bacterial concentration, sample volume, exposure time, and conditions on disinfection capacity was thoroughly investigated. Exposure to LED 2 resulted in substantial reductions in the viability of bacteria and yeast, demonstrating efficacy even against Clostridium perfringens endospores. Subsequently, an LED array was developed based on these findings and rigorously evaluated for efficacy, confirming its effectiveness as an efficient and environmentally friendly water treatment device.

Real-time underwater wireless optical communication and positioning an integrated system based on angular diversity SiPMs.

Underwater communication and positioning are essential for autonomous underwater vehicle (AUV) docking and formation. The traditional methods for communication and positioning are mainly independent from each other, increasing the redundancy and integration difficulty for AUVs. In this Letter, we demonstrate a real-time underwater wireless optical communication and positioning (UWOCP) integrated system. The LED array is adopted as a light source, and the pulse-position modulation (PPM) is used for a maximum transmission and sensing distance. By employing the silicon photomultiplier (SiPM) array, which consists of five SiPMs with different angles, the high sensitivity and ability to distinguish angles are obtained. Through calculating the relationship between the received pulse signal intensity of the five SiPMs, the pitch angle and yaw angle can be obtained. The experimental results in the pool show that the Ethernet bandwidth of 2.2 Mbps with an average angular error of 3.08° for one-dimensional positioning can be realized at a 50 m distance. To the best of our knowledge, this is the longest distance at which a real-time UWOCP system has been demonstrated. The proposed UWOCP system has the advantages of high sensitivity, computing efficiency, and compact structure, presenting great potential for underwater applications.

Full-color time-sequential super multi-view near-eye display with front-lit waveguide illumination

Light field (LF) displays can offer a quasi-natural three-dimensional (3D) viewing experience by tailoring the four-dimensional light information. However, the primary drawback of conventional LF displays is their limited image quality due to restricted information. To address this limitation, time-multiplexing techniques are employed, but the resulting system configurations are often impractical for achieving compact systems. Here, we present a compact time-sequential super multi-view LF near-eye display integrated with a front-lit, multi-directional illumination module for virtual reality application. This illumination module consists of an RGB light-emitting diode array and a waveguide, allowing us to exploit a high-speed reflective-type spatial light modulator and provide high-bit depth, full-color 3D scenes with quasi-continuous parallax in a compact form factor display. The prototype is implemented for a live demo and evaluated with both simulation and experiment. Our work provides a viable path towards the wide adoption of 3D virtual reality head-mounted displays.

Deep-Learning-Enhanced Visible Light Positioning System Based on the LED Array

Deep-Learning-Enhanced Visible Light Positioning System Based on the LED Array

Color-tunable ultralong-lifetime room temperature phosphorescence using phenylalanine derivative doped poly(vinyl alcohol) films

Doping chromophores in polymer matrixes to deliver room temperature phosphorescence (RTP) is well established. However, there are few examples of polymer-based RTP materials with ultralong phosphorescent lifetimes (>4 s) and afterglow (>30 s) under ambient conditions. We report a series of ultralong-lived RTP films by doping Phenylalanine (Phe) derivatives in a poly (vinyl alcohol) (PVA) matrix. The phosphorescence lifetime and efficiency of these films can be increased by introducing pentaerythritol (PER), an effect that is attributed to enhanced hydrogen-bonding interactions. The Fmoc-L-Phe@PER/PVA film exhibits a phosphorescence lifetime of 4.42 s and an afterglow duration of 46 s. Co-doping the PVA system with (Rhodamine B and Sulforhodamine B sodium salt) fluorescent dyes allows an adjustment of the afterglow from blue to red and pink. These films have been successfully applied in flexible luminescent materials, silk-screen printing, and multicolor afterglow light-emitting diode (LED) arrays.

Effect of Line-of-sight Channels on DC-biased Optical Filter Bank Multicarrier Visible Light Communication with Multiple LED Arrays

This paper investigates the impact of propagation delay and channel loss due to the use of multiple LED arrays in visible light communication (VLC) systems based on filter bank multicarrier (FBMC) modulation. FBMC offers greater spectral efficiency, and asynchronous transmission and is a promising alternative scheme to orthogonal frequency division modulation (OFDM). The proposed FBMC model is based on 4-quadrature amplitude modulation (QAM) and 16-QAM formats and uses 100 symbols and 600 input bits per symbol. In this paper, the VLC-FBMC system is designed based on the line-of-sight (LOS) model under the additive white Gaussian noise (AWGN) channel. Comparison analyses between different bit rates in terms of bit error rate (BER), best sampling point, and signal-to-noise ratio (SNR) requirement have been carried out to show the delay and loss effect on communication quality and system performance. The results demonstrate that the proposed FBMC model achieves a bit rate of up to 29.296 Mbit/s with a low BER of 10-3 and less SNR penalty in high QAM formats, demonstrating its potential as a viable alternative to OFDM for future VLC systems.

Constructing low-cost stable zinc-ion batteries with sodium-rich monoclinic manganese hexacyanoferrate cathode

Manganese-based Prussian blue analogues are ideal candidate cathode materials for constructing high-voltage zinc-ion batteries. However, challenges have persisted in realizing envisioned highly stable electrochemical cycling systems due to manganese dissolution under aqueous conditions and self-corrosion of zinc metal anodes. Considering practical application demands and cost-effectiveness, non-aqueous organic zinc-ion batteries have shown significant development potential by avoiding interference from active hydrogen and offering a stable wide voltage window. Herein, a sodium-rich monoclinic structured manganese hexacyanoferrate (m-MnHCF) was synthesized via a simple coprecipitation method, achieving a stable high-voltage zinc-ion battery energy storage system in a diluted 0.2 M Zn(CF3SO3)2 electrolyte in acetonitrile, a non-protonic polar solvent. The battery exhibited a discharge specific capacity of 77 mAh g−1 at the current density of 1 A g−1 after 620 cycles. Furthermore, by circumventing interference from active hydrogen, a cost-advantaged zinc powder anode (Zn-P) was successfully introduced into the energy storage system. Assembled Zn-P||m-MnHCF cells exhibited stable cycling for 100 cycles at a current density of 0.5 A g−1 with close to 100 % coulombic efficiency, showcasing limitless possibilities for the future, as demonstrated by illuminated LED arrays.

11‐3: Invited Paper: Advanced Micro LED Technologies for AR/MR Systems

A high quality micro LED array is essential for AR/MR systems. Either transparent or non‐transparent full‐color displays that are better than 3000 PPI require unique integration techniques that need to be optimized. The corresponding effects brought by these photonic components to the systems can be discussed in this talk.

공격 행동 인식 및 중재를 위한 IMU 기반 웨어러블 시스템 개발

The biggest type of behavior that prevents people with developmental disabilities from entering society is aggressive behavior. Aggressive behavior can pose a threat not only to the personal safety of the person with a developmental disability, but also to the physical safety of others. In this study, we propose a wearable system using a low-power processor. The proposed system uses an IMU (Inertial Measurement Unit) to analyze user behavior, and when attack behavior is not detected for a certain period of time through an LED array attached to the developed system, an interesting LED is displayed. By expressing patterns, we provide behavioral intervention through compensation to people with developmental disabilities. In order to implement a system that must be worn for a long time in a power-limited environment, we present a method to optimize performance and energy consumption across all stages, from data preprocessing to AI model application.

Miniaturized all-in-one microneedle device for point of care light therapy

Light therapies have been applied to millions of patients for treating many kinds of diseases, especially superficial ones. Currently, mainstream light therapies utilize the combined effects of photosensitizers and light to either remove disordered tissue or promote the growth of healthy tissue. Adverse effects of light therapy, including metabolic burden caused by circulatory photosensitizer and skin damage induced by high irradiance light, are yet to be addressed. This study provides a Miniaturized all-in-one Light therapy Device (MiLD). All components required for light therapy, including dual-function microneedles, LED array, control circuit, and battery are integrated together to form a miniaturized portable device with 2 cm in length, 1.7 cm in width, 1.2 cm in height, and 3.6 g in weight. The all-in-one design and patch-to-cure operation of MiLD enables the successful demonstration of point-of-care light therapy. Satisfactory therapeutic effects have been verified in mice on both types of light therapy. Meanwhile, transdermally co-delivering both photosensitizer and light in situ fully avoids photosensitizer accumulation in blood and remarkably reduces the irradiance of light, therefore significantly alleviating metabolic burden and light-induced skin damage. Overall, the MiLD lays the technical foundation of point-of-care light therapy with its miniaturized all-in-one design, simple patch-to-cure operation, satisfactory therapeutic effects, and minimum adverse effects.

Optimizing LED array irradiance uniformity with a particle swarm optimization-based scheme: application in a parallel photoreactor

This study proposes a particle swarm optimization (PSO)-based method for enhancing the irradiance uniformity of light emitting diode (LED) arrays in parallel photoreactors. We construct a spatial irradiance model, validating its accuracy with near-field optical test data and optical simulation results. An evaluation function for irradiance uniformity guides the iterative optimization of the LED arrangement, taking into consideration practical constraints such as chip size, heat dissipation, and circuit board wiring. The optimized LED array demonstrated a significant improvement in irradiance uniformity, increasing from 75.27% to 95.61%. This showcases the feasibility and effectiveness of our PSO-based method for practical applications in optimizing LED arrays.