Power Light-emitting Diodes Research Articles

Research on a frequency-increasing piezoelectric wave energy harvester based on gear mechanism and magnetic rotor

Abstract Wave energy is a widespread clean energy source, but harvesting low-frequency wave energy efficiently remains a challenge. In this paper, a frequency-increasing piezoelectric wave energy harvester (FPWEH) based on gear mechanism and magnetic rotor is proposed. The gear mechanism transforms the vertical motion of the wave into the higher-frequency rotational motion of the magnetic rotor. The magnetic rotor is equipped with several rotating magnets and one revolution of the magnetic rotor enables multiple excitations of the piezoelectric cantilevers. Therefore, the wave excitation frequency is increased, so that the FPWEH can obtain better output performance. The major factors influencing output performance are determined through theoretical and simulation analysis, and a test system to simulate the wave environment is established. According to experimental findings, the FPWEH can generate an output voltage of 69.82 V and a maximum power of 28.33 mW when the external resistance is 20 kΩ. It can also successfully power thermohygrometer and light-emitting diodes (LEDs). These results validate the feasibility of the FPWEH for providing electricity to electronics with low power requirements. This research also offers a novel approach to harvesting low-frequency wave energy.

An enclosed solid-liquid triboelectric nanogenerator based on Janus-type TPU nanofibers

Various environmental factors such as high humidity, rain, snow, and other conditions restrict the practical use of triboelectric nanogenerator (TENG). Herein, Janus-type thermoplastic polyurethane (TPU) nanofiber films with good hydrophobicity were fabricated by side-by-side electrospinning. The output performance of TENG based on Janus-type TPU nanofiber films was much higher than that made of normal TPU nanofiber films. A flexible enclosed TENG was prepared that maintained its output performance regardless of external humidity. What’s more, liquid metal gallium (Ga) was injected into the enclosed TENG and used as the tribo-material. The addition of Ga to the enclosed TENG increased its output performance to reach a peak voltage of 282 V and current of 6.0 μA. The enclosed TENG was able to power light-emitting diodes (LEDs) even when immersed in water, demonstrating its potential for using under high-humidity conditions.

Utilizing a high power light-emitting diode to induce apoptosis of uterine carcinosarcoma (malignant mixed mullerian tumor) cells through a bi-phasic effect

Utilizing a high power light-emitting diode to induce apoptosis of uterine carcinosarcoma (malignant mixed mullerian tumor) cells through a bi-phasic effect

Valorization of Food Waste: Utilizing Natural Porous Materials Derived from Pomelo-Peel Biomass to Develop Triboelectric Nanogenerators for Energy Harvesting and Self-Powered Sensing.

Food waste is an enormous challenge, with implications for the environment, society, and economy. Every year around the world, 1.3 billion tons of food are wasted or lost, and food waste-associated costs are around $2.6 trillion. Waste upcycling has been shown to mitigate these negative impacts. This study's optimized pomelo-peel biomass-derived porous material-based triboelectric nanogenerator (PP-TENG) had an open circuit voltage of 58 V and a peak power density of 254.8 mW/m2. As porous structures enable such triboelectric devices to respond sensitively to external mechanical stimuli, we tested our optimized PP-TENG's ability to serve as a self-powered sensor of biomechanical motions. As well as successfully harvesting sufficient mechanical energy to power light-emitting diodes and portable electronics, our PP-TENGs successfully monitored joint motions, neck movements, and gait patterns, suggesting their strong potential for use in healthcare monitoring and physical rehabilitation, among other applications. As such, the present work opens up various new possibilities for transforming a prolific type of food waste into value-added products and thus could enhance long-term sustainability while reducing such waste.

A triboelectric nanogenerator based on a spiral rotating shaft for efficient marine energy harvesting of the hydrostatic pressure differential

Equipment used in underwater sensing and exploration typically relies on cables or batteries for energy supply, resulting in a limited and inconvenient energy supply and marine environmental pollution that hinder the sustainable development of distributed ocean sensing networks. Here, we design a deep-sea differential-pressure triboelectric nanogenerator (DP-TENG) based on a spiral shaft drive using modified polymer materials to harness the hydrostatic pressure gradient energy at varying ocean depths to power underwater equipment. The spiral shaft structure converts a single compression into multiple rotations of the TENG rotor, achieving efficient conversion of differential pressure energy. The multi-pair electrode design enables the DP-TENG to generate a peak current of 61.7 μA, the instantaneous current density can reach 0.69 μA cm−2, and the output performance can be improved by optimizing the spiral angle of the shaft. The DP-TENG can charge a 33 μF capacitor to 17.5 V within five working cycles. It can also power a digital calculator and light up 116 commercial power light-emitting diodes, demonstrating excellent output capability. With its simple structure, low production cost, and small form factor, the DP-TENG can be seamlessly integrated with underwater vehicles. The results hold broad prospects for underwater blue energy harvesting and are expected to contribute to the development of self-powered equipment toward emerging “smart ocean” and blue economy applications.

Scalable Metal Free Zinc Ion Capattery Enabled by Interstitial Defect Engineering of Nanoscale n-Type Zinc Vanadate.

This Letter explores the energy storage properties of nano zinc vanadate in zinc metal batteries and a Zn metal free capattery. The synthesis is a simple scalable solution state mechanochemical route with uniform nanosized one-dimensional zinc vanadate. The synthesized vanadate is engineered using NMP at the electrode fabrication stage to position the Zn2+ ions at an easily extractable site. This in turn tunes the bandgap from 2.38 to 2.16 eV, creating oxygen defective vacancies in the crystal lattice. In addition, electrochemical analysis of the engineered cathode is studied in a half-cell device that is further developed into a zinc metal free zinc ion capattery (ZiC). The developed metal free capattery delivered a capacity of 120 mAh g-1 at a current density of 100 mA g-1, and a pouch cell is fabricated to power light-emitting diodes.

K-Means-Based DNN Algorithm for a High Accuracy VLP System

In this paper, a positioning algorithm based on the combination of K-means clustering and deep neural networks (DNNs) is first presented for multiple light emitting diodes (LEDs) integrated with visible light positioning (VLP) systems. We extracted the maximum value from the collected optical power of LEDs, utilizing the ratio of each optical power to this maximum optical power as the input training data. The experimental results demonstrate that the proposed algorithm outperformed the conventional DNN algorithm in terms of anti-jamming capability and positioning accuracy. In addition, the positioning accuracy of the proposed system reached a millimeter level, which is the highest experimental VLP accuracy, to the best of our knowledge.

Boosted triboelectric output performance in g-C3N4 embedded P(VDF-TrFE) composite via a coupling of photocarrier and ferroelectric dipole

Innovative material design is one of the most plausible routes to sufficiently enhance triboelectric outputs for self-powered electronic devices. Herein, we reported a g-C3N4 embedded P(VDF-TrFE) composite as a strong candidate for boosting the output power via simultaneous harvesting of mechanical and light energies. Visible light-responsive g-C3N4 nanosheets are chemically bonded to the ferroelectric P(VDF-TrFE) polymer and increase the ferroelectric polarization and dielectric constant of the composite. Kelvin probe force microscopy and photoluminescence measurements reveal that the enhanced triboelectric output is related to the increased workfunction, the reduced recombination rate of electron-hole pairs, and the band bending-induced photocarrier movement. The up-poled g-C3N4@P(VDF-TrFE) composite-based photoactive triboelectric nanogenerator (PA-TENG) generates a power (power density) of 2.0 mW (0.125 mW/cm2) under a blue light illumination, which is 10 times larger than PA-TENG under a dark condition and 54 times larger than bare P(VDF-TrFE)-based TENG. The output power is continued for at least up to 1.5 months in ambient conditions and is enough to power light-emitting diodes, a thermo-hygrometer, and a digital watch, which would be quite useful for individuals in the dark underground. This work provides a novel approach to boost the triboelectric output via a coupling of photocarrier and ferroelectric dipole and a useful hint to realize self-powered small electronics for safety issues in dark environments like caves and tunnels.

Структура и элементная база приёмо-передающего модуля для организации подводной оптической беспроводной системы передачи данных

In the paper, the results of theoretical study of a wireless optical data transmission channel, as well as experimental study of its characteristics, taking into account different configurations of the optical component base of receiving and transmitting modules, were presented. The model of the wireless underwater optical communication channel with pulse-position modulation (4 bits per symbol) of digital data traffic with 100 Mbps is proposed. The model showed that to organize a communication channel on a 10 m path, the use of an array of light-emitting diodes (LEDs) is requires (the amount is up to 20 LEDs). For this case, a sufficiently large route budget will be provided, even with additional factor that reduce the efficiency of light propagation in seawater. The LEDs were chosen to organize the data transmission channel, since they have a wide radiation pattern and allow the implementation of a relatively simple driver circuit. The required optical radiation power is realized with the use of an array of LEDs. Schematic diagrams of the LEDs driver and power supply for the receiving and transmitting modules have been designed. A measuring layout with optical transmitter and receiver blocks has been implemented. The test signal is a regular sequence of pulses with a duty cycle of 2, and a frequency of 1 MHz. In the receiving module, the signal from the output of the pin photodiode is amplified using a wideband operational amplifier. Sets of 3 pin photodiodes and 10 LEDs were selected and tests were carried out to determine options for optical components that provide the best time characteristics of the output electrical signal in terms of delay time, rising and falling edges of pulses in a wireless optical airborne communication channel. Also, measurements were done on an air path with a length of 0.25-3 m using one or two LEDs as part of the transmitting module. It has been experimentally confirmed that the organization of a communication channel with a length of up to 10 m requires about 15-20 light-emitting diodes. Further study involves the designing and testing of a driver for the LEDs array and a prototype transceiver module.

Insight into the optical evaluation of sunlike LED devices with full-visible spectrum emission based on ultra-low melting tin fluorophosphate glass for human centric lighting

Full spectrum sunlike light-emitting diode (LED) devices in the wavelength range of 380–670 nm have received much attention for their applications in human centric lighting. Herein, the inorganic color converter of the sunlike phosphor-in-glass (PiG) has been developed by embedding the green-emitting (Lu3-xYxAl5O12: Ce3+) and red-emitting (Sr0.6Ca0.4AlSiN3: Eu2+) phosphor powders in ultra-low melting tin fluorophosphate glass. Notably, the sunlike PiG exhibits the full spectrum in the wavelength range of 380–670 nm under the excitation of a near-ultraviolet (NUV) chip. Tunable color temperature (2785 K–5806 K) and high color rendering index (Ra = 95) were obtained by varying the mix ratio of the red-emitting component in the glass matrix. Further, the full visible spectrum emission was regulated by adjusting the Lu/Y ratio of the green phosphor Lu3-xYxAl5O12: Ce3+ and the color quality was further optimized (Ra = 97). The color quality of white light-emitting diode (WLED) was systematically investigated using Illuminating Engineering Society (IES) of North America evaluation systems and the LED devices exhibit fidelity index (Rf) and gamut index (Rg) close to sunlight (Rf = 95, Rg = 101). Compared with the traditional phosphor-in-silicone (PiS), the sunlike PiG based WLED exhibits a low working temperature of ∼37 °C for high power LED. Therefore, the WLED devices based on sunlike-PiG can be regarded as promising candidates for ultra-high color rendering index light sources because of the adjustable color temperature, high color quality, low-efficiency loss, excellent thermal properties and water stability.

Enhanced piezoelectric energy harvesting using hybrid composites of MWCNTs and partially-reduced GO in RTV-SR for stable voltage generation

Recent studies have explored the use of flexible devices for piezoelectric energy harvesting, which can generate energy at a few volts on a laboratory scale. In this context, multiwall carbon nanotubes (MWCNTs), partially-reduced GO (p-rGO), and their hybrid composites based on room temperature vulcanized silicone rubber (RTV-SR) have emerged as innovative and novel approaches for energy production. The composites were prepared by mixing an RTV-SR solution with MWCNTs and p-rGO powder as fillers, resulting in improved mechanical properties and reinforcement of the RTV-SR matrix. The p-rGO was synthesized from graphite nanoplatelets (GNP) using the modified Hummers' method, followed by chemical and thermal reduction. The MWCNTs were used as received from the supplier. Characterization techniques such as scanning electron microscopy, x-ray diffraction, transmission electron spectroscopy, and atomic force microscopy revealed that the p-rGO consisted of less than five layers stacked in a crystalline domain. Static mechanical property analysis demonstrated that MWCNTs exhibited exceptional filler characteristics compared to other fillers studied. Piezoelectric energy harvesting measurements were performed, and the results indicated higher voltage generation for MWCNTs; however, it exhibited instability and a decline in performance after a few cycles due to electrode cracking. In contrast, the hybrid composite demonstrated stable voltage generation. Moreover, walking and running activities may generate renewable, simple, and sufficient voltage to power light-emitting diodes (LEDs).

Antibiotic-Powered Energy Harvesting: Introducing Benzylpenicillin as an Efficient Tribopositive Material for Triboelectric Nanogenerators

The pursuit of enhancing the performance of triboelectric nanogenerators (TENGs) has led to the exploration of new materials with efficient charge-generating capabilities. Herein, we propose benzylpenicillin sodium salt (b-PEN) as a candidate biomaterial for the tribopositive layer owing to its superior electron-donating capability via the lone pairs of electrons on its sulfur atom, carbonyl, and amino functional groups. The proposed b-PEN TENG device exhibits promising electrical performance with an open-circuit voltage of 185 V, a short-circuit current of 4.52 µA, and a maximum power density of 72 µW/cm2 under force applied by a pneumatic air cylinder at 5 Hz. The biomechanical energy-harvesting capabilities of the b-PEN TENG device are demonstrated by actuating it with finger, hand, and foot movements. Moreover, the proposed TENG device is utilized to charge capacitors and power light-emitting diodes by scavenging the externally applied mechanical energy. This outstanding electrical performance makes b-PEN a promising tribopositive material.

Ground-facing radiative cooling for high power LED lights

Objects on Earth facing the sky have the ability to emit thermal energy into the universe through the transparent atmosphere. This process can enable electricity-free cooling due to the extremely low temperature of outer space. However, factors such as humidity, clouds, and air pollution within the atmosphere can affect this process, particularly for electricity-free sub-ambient cooling applications. For high-temperature objects, the dependency of radiative cooling performance on the environment is significantly reduced. In this study, we explore the potential of utilizing ground-facing radiative cooling for improved high-power light-emitting-diode (LED) lighting applications. By using a transparent material, like polyethylene, as the front cover of the LED light package, one can efficiently release thermal radiation from the semiconductor chips that can reach temperatures of 60–130 °C. As a result, we demonstrate a reduction in the operational temperature of the LED chip by 3.9 °C in controlled indoor settings and by 3.7 °C in selected outdoor environments. Our analysis reveals that employing ground-facing radiative cooling can enhance the luminous efficacy of LED lights by approximately 3.0%. Assuming all current global electricity consumption is used for LED lights, this enhancement translates to an estimated annual energy savings of 128 terawatt-hours and a reduction in carbon dioxide emissions by 55 million metric tons. Remarkably, according to our aging experiment over 4000 h, this method can extend the lifespan of LED lights by 21.7% due to the lowered junction temperature of the semiconductor chip, resulting in reduced material, labor, and maintenance costs for future global LED lighting products.

Isı Emici-Isı Borulu İnovatif Bir Yüksek Güçlü LED Termal Yönetim Sisteminin Deneysel ve Nümerik Analizi

The efficiency and lifespan of light emitting diodes (LEDs) are adversely affected by the junction temperature. Therefore, it is very important to operate a LED at a low junction temperature. In this study, it is aimed to minimize the junction temperature of high power LEDs so that reliability and light output of the device can be maximized.
 In the study, a heat pipe-heat sink cooler was designed for the high power LEDs. The study was carried out experimentally and the results obtained from the experimental study were also verified numerically in the ANSYS Fluent software. Total power inputs ranging between 40 W and 100 W were applied to the LEDs and the performance of the cooler in the current design was examined. To observe the effect of the heat pipe on the LED junction temperature, a heat sink without heat pipe was designed and analyzed both experimentally and numerically. The results show that, the heat sink with fin is sufficient at low LED input powers, while at high LED input powers, the heat pipe-heat sink provides much more effective cooling. At the same time, the effect of different thermal interface materials on LED junction temperature was observed, by using with materials with thermal conductivities of 1.8 W/m.K, 8.5 W/m.K and 11 W/m.K, for each power input. As the coefficient of thermal conductivity of the thermal interface materials increased, the temperature of the LED solder point decreased.

Single Quasi-Symmetrical LED with High Intensity and Wide Beam Width Using Diamond-Shaped Mirror Refraction Method for Surgical Fluorescence Microscope Applications.

To remove tumors with the same blood vessel color, observation is performed using a surgical microscope through fluorescent staining. Therefore, surgical microscopes use light emitting diode (LED) emission and excitation wavelengths to induce fluorescence emission wavelengths. LEDs used in hand-held type microscopes have a beam irradiation range of 10° and a weak power of less than 0.5 mW. Therefore, fluorescence emission is difficult. This study proposes to increase the beam width and power of LED by utilizing the quasi-symmetrical beam irradiation method. Commercial LED irradiates a beam 1/r2 distance away from the target (working distance). To obtain the fluorescence emission probability, set up four mirrors. The distance between the mirrors and the LED is 5.9 cm, and the distance between the mirrors and the target is 2.95 cm. The commercial LED reached power on target of 8.0 pW within the wavelength band of 405 nm. The power reaching the target is 0.60 mW in the wavelength band of 405 nm for the LED with the beam mirror attachment method using the quasi-symmetrical beam irradiation method. This result is expected to be sufficient for fluorescence emission. The light power of the mirror was increased by approximately four times.

Numerical Modeling and Simulation of Non-Invasive Acupuncture Therapy Utilizing Near-Infrared Light-Emitting Diode.

Acupuncture is one of the most extensively used complementary and alternative medicine therapies worldwide. In this study, we explore the use of near-infrared light-emitting diodes (LEDs) to provide acupuncture-like physical stimulus to the skin tissue, but in a completely non-invasive way. A computational modeling framework has been developed to investigate the light-tissue interaction within a three-dimensional multi-layer model of skin tissue. Finite element-based analysis has been conducted, to obtain the spatiotemporal temperature distribution within the skin tissue, by solving Pennes' bioheat transfer equation, coupled with the Beer-Lambert law. The irradiation profile of the LED has been experimentally characterized and imposed in the numerical model. The experimental validation of the developed model has been conducted through comparing the numerical model predictions with those obtained experimentally on the agar phantom. The effects of the LED power, treatment duration, LED distance from the skin surface, and usage of multiple LEDs on the temperature distribution attained within the skin tissue have been systematically investigated, highlighting the safe operating power of the selected LEDs. The presented information about the spatiotemporal temperature distribution, and critical factors affecting it, would assist in better optimizing the desired thermal dosage, thereby enabling a safe and effective LED-based photothermal therapy.

BASIC PRINCIPLES OF CONSTRUCTION OF MODULAR HARDWARE COMPLEXES FOR LED THERAPY

The industrial production of powerful light-emitting diodes has led to the appearance of devices for therapeutic purposes, where such diodes are used as sources of electromagnetic radiation in the optical range. The development and production of such devices was established in the city of Kharkiv with the participation of scientists and specialists of Kharkiv National University named after V.M. Karazin and National Technical University "Kharkiv Polytechnic Institute". Methods of using devices and hardware complexes in medical practice were created at the Kharkiv Medical Academy of Postgraduate Education. The article analyzes the main principles of building modular hardware complexes for LED therapy, defines structures and options for connecting modules. As a result of the work performed, it was established that the modular implementation of hardware complexes for LED therapy has five main options, which differ in the number and types of emitters connected to the control unit, in the connection scheme of photon emitters, and in their functionality. It was also noted that the modular principle of building hardware complexes for LED therapy makes it quite easy to carry out their modernization and form the necessary configuration of the irradiating system, that is, to significantly expand the functional capabilities of the complex for carrying out phototherapy treatment procedures with the greatest efficiency. The expediency of using microprocessor technology for the implementation of the information part of the control unit of the complex is shown. This makes it possible to ensure the operation of photon emitters in continuous, pulsed and scanning modes, as well as separate operation of the emitters of the irradiation system of the complex and irradiation of the patient in biosynchronization mode.

Dynamic Pluronic F127 Crosslinking Enhancement of Biopolymeric Nanocomposites for Piezo‐Triboelectric Single‐Hybrid Nanogenerators and Self‐Powered Sensors (Small 21/2023)

Biopolymeric Nanocomposites In article number 2207384, Qufu Wei, Pengfei Lv, and co-workers report on biopolymeric composites for triboelectric nanogenerators (TENGs), piezoelectric nanogenerators (PENGs), and hybrid formats with outstanding mechanical and electrical properties. The designed composites are poling-responsive, outperform many reported biopolymer formats in voltage, currents, and power outputs. The materials demonstrate impressive energy storage capabilities, seamlessly interface with commercial microcontrollers, and power light-emitting diodes (LEDs). The devices and their functionalities advance the development of fully biopolymeric nanogenerators.

Research on Light Extraction of GaN-based LED with Surface/Interface Coarsening

Light-emitting diodes (LEDs) are a highly versatile light source that have been widely employed in various fields. In order to maximize its quantum efficiency, it is essential to boost the efficiency of light extraction. Internal photon reflection can have a distinct negative impact on the luminous output power of GaN-based LEDs, which can be addressed by surface and interface texturing of different LED layers. This article discusses the mechanisms of light extraction losses in GaN-based LEDs and summarizes various surface and interface coarsening techniques proposed for improving the light extraction rate, including a range of physical and chemical etching methods.

A Review on the Progress of AlGaN Tunnel Homojunction Deep-Ultraviolet Light-Emitting Diodes

Conventional deep-ultraviolet (UV) light-emitting diodes (LEDs) based on AlGaN crystals have extremely low light-emission efficiencies due to the absorption in p-type GaN anode contacts. UV-light-transparent anode structures are considered as one of the solutions to increase a light output power. To this end, the present study focuses on developing a transparent AlGaN homoepitaxial tunnel junction (TJ) as the anode of a deep-UV LED. Deep-UV LEDs composed of n+/p+-type AlGaN TJs were fabricated under the growth condition that reduced the carrier compensation in the n+-type AlGaN layers. The developed deep-UV LED achieved an operating voltage of 10.8 V under a direct current (DC) operation of 63 A cm−2, which is one of the lowest values among devices composed of AlGaN tunnel homojunctions. In addition, magnesium zinc oxide (MgZnO)/Al reflective electrodes were fabricated to enhance the output power of the AlGaN homoepitaxial TJ LED. The output power was increased to 57.3 mW under a 63 A cm−2 DC operation, which was 1.7 times higher than that achieved using the conventional Ti/Al electrodes. The combination of the AlGaN-based TJ and MgZnO/Al reflective contact allows further improvement of the light output power. This study confirms that the AlGaN TJ is a promising UV-transmittance structure that can achieve a high light-extraction efficiency.