Efficacy Of Light-emitting Diodes Research Articles

Effectiveness of Light-Emitting Diode Epilation on Different Skin Types: A Pilot Study.

Objective: This study analyzed the histological and immunohistochemical changes in hair follicles submitted to epilation with light-emitting diode (LED). Background: The use of specific wavelengths of LED leads to the absorption of photons by chromophore tissues, enabling different photophysical and photochemical events, bringing therapeutic benefits such as removing body hair. Methods: The sample included five participants, with phototypes II-V, divided into two groups. The volunteers received a session of epilation with the Holonyak® device on the pubic region and right groin, whereas the contralateral side was kept as a control. An energy of 10 J and a cooling temperature of -5°C were used, after which the pain provoked by the equipment was questioned using the analogue pain scale. After 45 days, the punching procedure was performed in the region where skin samples were taken for histological and immunohistochemical analysis. Results: For all phototypes, in the treated area, the follicles and sebaceous glands were in a stage of involution, showing perifollicular inflammatory infiltrate with changes suggestive of apoptosis. The apoptosis process was confirmed by the increase in markers cytokeratin-18 and cleaved caspase 3, in addition to the reduced expression of Blc-2, and the lower cell proliferation (Ki67), reinforcing the action of LED based on the definite involution and resorption of the follicle, through macrophages (CD68) triggered by the inflammatory process. Conclusions: The preliminary results of this study found relevant histological changes and immunohistochemical markers in the epilation process, which may indicate the efficacy of LED in permanent hair removal.

Characterization of Spectroradiometric Based Luminous Flux Measurements for LED Luminaires at BRIN Indonesia

Light Emitting Diode (LED) luminaires are known to have higher efficacy compared to other types of light sources. Therefore, this type of luminaire has been deployed to replace existing conventional types of light sources as means of energy-saving around the world. LED efficacy is commonly measured using a photometer mounted in a goniophotometer or an integrating sphere system. However, due to the different spectral properties of the LEDs compared with the source used in the photometer calibration, mismatch correction needs to be applied in the measurement process. Due to the arduous process of obtaining the correction, the measurement of luminous flux using a spectroradiometer is proposed in this study. By utilizing this device, the mismatch correction does not need to be applied. The measurements of several commercially available LED and energy-saving compact fluorescent luminaires (CFL) show that current LED has twice the efficacy of the CFLs. The LED shows efficacy in the range of 114 lumen/watt. The measurement uncertainty associated with the efficacy of the LED is 4.2%. It is expected that the quality assurance and the accuracy of LEDs luminaires measurement and testing in Indonesia can be improved by using the integrating sphere with the spectroradiometer measurement method.

Applications of light emitting diodes and their mechanism for food preservation

AbstractIn the food sector, light emitting diodes (LEDs) have a wide range of uses, including improving food production, extending the shelf life of perishables, and—most importantly—improving food safety. LEDs are semiconductor devices that, depending on the kind of conductors they are built of, emit light by electroluminescence across a range of wavelength spectrums. Compared to conventional light sources (ultraviolet [UV] light), LEDs are more energy‐efficient, eco‐friendly and have a lesser environmental impact. Moreover, LEDs have relatively lower warm up time and heat emissions, higher life expectancy and no mercury deposits compared to UV light. This article provides a comprehensive review of the food safety applications of LED showcasing its potential in microbial inactivation of clear, liquid food products as a potential alternative to traditional UV‐light technology. Optical properties (cloudiness, penetration depth of light) of the foods and geometrical design of the LED treatment chamber (distance from light source and intensity, wavelength of the light) play a key role in maximizing LED's efficacy for microbial inactivation. Additionally, a combination of wavelengths and photosensitizing compounds have proven to be synergistic in the application of this technology. There is a need for further research on the effect of LEDs on the safety and quality attributes of food and beverage products to continue with the feasibility assessment required to determine its potential at industrial scale.

Lambertian Luminous Intensity Radiation Pattern Analysis in OLOS Indoor Propagation for Better Connectivity

This paper illustrates the impact of wavelength on the Optical Line of sight (OLOS) link working in the Visible Light Communication (VLC) spectrum. The extension of work is based on previous outcomes given by researchers. It has been elaborated with different determinants based on the color factor of LED available in the Visible Light (VL) spectrum. In the modern world, Light Emitting Diodes (LEDs) are prevailing the market as a light source, which is dominantly used at homes and workplaces. The designed VLC system includes LED as a transmitter, which is used as a higher source of brightness and provides both illuminations and data communication. Solid-state lighting characteristic shows the electroluminance capability of high brightness LEDs. Within few years, the luminous efficacy of LED is exponentially increasing from the range of less than 0.1 lm/W to over 230 lm/W with a huge lifetime of around 100,000 h. MATLAB is used to simulate a VLC link between LEDs (operated at different wavelengths) and photodetector. We present here the performance analysis of Lambertian Luminous Intensity radiation pattern (LLIRP) generated by different colors of LED for a clear OLOS model with different Spectral Luminous Efficiency at photonic vision. A designed system model of VLC supports short links present in indoor room conditions with better connectivity.

Narrowband Blue and Red LED Supplements Impact Key Flavor Volatiles in Hydroponically Grown Basil Across Growing Seasons.

The use of light-emitting diodes (LEDs) in commercial greenhouse production is rapidly increasing because of technological advancements, increased spectral control, and improved energy efficiency. Research is needed to determine the value and efficacy of LEDs in comparison to traditional lighting systems. The objective of this study was to establish the impact of narrowband blue (B) and red (R) LED lighting ratios on flavor volatiles in hydroponic basil (Ocimum basilicum var. “Genovese”) in comparison to a non-supplemented natural light (NL) control and traditional high-pressure sodium (HPS) lighting. “Genovese” basil was chosen because of its high market value and demand among professional chefs. Emphasis was placed on investigating concentrations of important flavor volatiles in response to specific ratios of narrowband B/R LED supplemental lighting (SL) and growing season. A total of eight treatments were used: one non-supplemented NL control, one HPS treatment, and six LED treatments (peaked at 447 nm/627 nm, ±20 nm) with progressive B/R ratios (10B/90R, 20B/80R, 30B/70R, 40B/60R, 50B/50R, and 60B/40R). Each SL treatment provided 8.64 mol ⋅ m−2 ⋅ d–1 (100 μmol ⋅ m–2 ⋅ s–1, 24 h ⋅ d–1). The daily light integral (DLI) of the NL control averaged 9.5 mol ⋅ m−2 ⋅ d–1 during the growth period (ranging from 4 to 18 mol ⋅ m−2 ⋅ d–1). Relative humidity averaged 50%, with day/night temperatures averaging 27.4°C/21.8°C, respectively. Basil plants were harvested 45 days after seeding, and volatile organic compound profiles were obtained by gas chromatography–mass spectrometry. Total terpenoid concentrations were dramatically increased during winter months under LED treatments, but still showed significant impacts during seasons with sufficient DLI and spectral quality. Many key flavor volatile concentrations varied significantly among lighting treatments and growing season. However, the concentrations of some compounds, such as methyl eugenol, were three to four times higher in the control and decreased significantly for basil grown under SL treatments. Maximum concentrations for each compound varied among lighting treatments, but most monoterpenes and diterpenes evaluated were highest under 20B/80R to 50B/50R. This study shows that supplemental narrowband light treatments from LED sources may be used to manipulate secondary metabolic resource allocation. The application of narrowband LED SL has great potential for improving overall flavor quality of basil and other high-value specialty herbs.

Light-emitting diode photobiomodulation therapy for non-specific low back pain in working nurses: A single-center, double-blind, prospective, randomized controlled trial.

Background:Low back pain (LBP) affects approximately 51% to 57% of hospital nurses and nurses’ aides in Europe. New high-risk groups include home- and long-term-care nurses and physiotherapists. A number of European countries are experiencing a shortage of healthcare workers. Light therapy has been shown to be an effective treatment for various musculoskeletal disorders, including lateral epicondylitis, temporomandibular joint pain, carpal tunnel syndrome, and delayed-onset muscle soreness. A systematic review and meta-analysis demonstrated that low-level laser therapy is an effective method for relieving non-specific chronic low back pain (NSCLBP). However, the efficacy of light-emitting diode (LED) therapy for NSCLBP is disputed. This study aims to evaluate the effect of LED therapy on NSCLBP.Methods and analysis:We conducted a prospective, double-blind, randomized placebo-controlled trial of 148 patients with NSCLBP. The patients were randomly assigned to 2 groups: intervention group, where patients received LED photobiomodulation therapy 3 times a week for 2 weeks, and the sham group, where patients had sham therapy 3 times a week for 2 weeks. Primary outcome measures included the visual analog scale for pain, lumbar active range of motion assessments, and chair-rising times. Secondary outcome measures included a multidimensional fatigue inventory, fear-avoidance beliefs questionnaire, and the Oswestry disability index. The outcome measures were assessed before therapy and 2weeks, 4 weeks, 8 weeks, 12 weeks, and 6 months after the first interventions were completed.Discussion:This study is a prospective, single-center, double-blind, randomized, controlled study. This study aims to research the efficacy of a 2-week LED program for NSCLBP working nurse. Our results will be useful for patients, working nurses, nurses’ aides, and other healthcare workers with chronic low back pain.Trial registration number:NCT04424823

Optimized double-sided pattern design on a patterned sapphire substrate for flip-chip GaN-based light-emitting diodes

This study reports on the development and testing of a cost- and time-effective means to optimize a double-sided hemispherical patterned sapphire substrate (PSS) for highly efficient flip-chip GaN-based light-emitting diodes (LEDs). A simulation is conducted to study how light extraction efficiency (LEE) changed as a function of alteration in the parameters of the unit hemisphere for LEDs that are fabricated on a hemispherical PSS. Results show that the LEE of LED flip chip could be enhanced with the optimized hemispherical PSS by over 0.508 and is ∼115.3% higher than that of flip-chip LEDs with non-PSS. This study confirms the high efficiency and excellent capability of the optimized hemispherical PSS pattern to improve LED efficacy.

Regulation of lipid production by light-emitting diodes in human sebocytes.

Light-emitting diodes (LED) have been used to treat acne vulgaris. However, the efficacy of LED on sebaceous lipid production in vitro has not been examined. This study investigated the efficacy of 415 nm blue light and 630 nm red light on lipid production in human sebocytes. When applied to human primary sebocytes, 415 nm blue light suppressed cell proliferation. Based on a lipogenesis study using Oil Red O, Nile red staining, and thin-layered chromatography, 630 nm red light strongly downregulated lipid production in sebocytes. These results suggest that 415 nm blue light and 630 nm red light influence lipid production in human sebocytes and have beneficial effects on acne by suppressing sebum production.

Heat dissipation performance of a high-brightness LED package assembly using high-thermal conductivity filler

This paper presents a thermal analysis and experimental validation of natural convective heat transfer of a high-brightness light-emitting diode (LED) package assembly. The substrate materials used in the LED package assembly were filled and doped using boron nitride (BN) filler. The thermal conductivity of the BN-filled substrate was measured. The temperature distribution and heat flow of the LED package were assessed by thermal profile measurement using an infrared (IR) camera and thermocouples. In addition, the heat transfer process of the LED package assembly in natural convection was also simulated using the computational fluid dynamics method. The optical performance of the LED package was monitored and investigated with various filler contents. The heat conduction mechanism in the substrate was analyzed. IR thermogram showed that the BN-doped substrate could effectively lower the surface temperature of the LED package by 21.5°C compared with the traditional FR4 substrate. According to the IESNA LM 80 lifetime testing method, reduction in LED temperature can prolong the LED's lifetime by 19,000h. The optical performance of the LED package assembly was also found to be improved significantly in lighting power by 10%. As a result, the overall heat dissipation capability of the LED package to the surrounding is enhanced, which improves the LED's efficacy.

Enhance Light Emitting Diode Light Extraction Efficiency by an Optimized Spherical Cap-Shaped Patterned Sapphire Substrate

This work has proposed a new way to optimize the spherical cap-shaped patterned sapphire substrate (PSS) for highly efficient GaN-based light emitting diodes (LEDs), which has been compared with the hemisphere patterned one. This pattern is achieved by changing the height of hemispherical units on the basis of hemispherical PSS. The height, the distance and the radius of the spherical cap-shaped unit are subsequently optimised by optical simulation. It is revealed that this optimised spherical cap-shaped PSS can enhance light extraction yield of LEDs by over 10% compared with LEDs grown on the optimal hemispherical PSS. The effectiveness of this spherical cap-shaped PSS has been demonstrated by subsequent crystal growth and characterization of LED wafers, and therefore sheds light on a further improvement on LED efficacy by the design of novel patterns for the application of PSS technology.

Polychromatic LED in Oval Full-Thickness Wound Healing in Non-diabetic and Diabetic Rats

Our goal was to determine the efficacy of polychromatic light-emitting diode (LED) in the enhancement of wound healing in non-diabetic and diabetic rats. LEDs are increasingly used as an alternative light source for phototherapy. A cluster of 25 LED photons at 510-543, 594-599, 626-639, 640-670, and 842-872 nm wavelengths with 272-mW output power was used. Male Sprague-Dawley rats (n = 61) were randomly assigned into non-diabetic and diabetic groups and into light treatment groups, that is, control, 5, 10, 20, and 30 J/cm(2). Streptozotocin was used for diabetes induction. Wounds were created using a scalpel after 1 week of wounding. Wounds were measured daily and plotted in time, and the trendline was fitted to obtain slope values. Relative wound healing percentage was computed as follows: RWH% = [(Slope treated - Slope control)/(Slope control)] x 100. The t-test (alpha = 0.05) was used for analysis. The RWH% in the non-diabetic rats was insignificant (p > 0.05) at 5, 10, 20, and 30 J/cm(2) treatments, giving 4.3 +/- 1.97%, 5.4 +/- 1.94%, 4.5 +/- 1.96%, and 1.2 +/- 2.03%, respectively. The healing of diabetic rats was significantly impaired by -11.7 +/- 3.25% (p = 0.02), which was mitigated by 5 J/cm(2) treatment (2.4 +/- 3.02%, (p) = 0.40) and 10 J/cm(2) treatment (-5.5 +/- 3.28%, p = 0.11). Diabetic wound healing using 20 J/cm(2) (-8.7 +/- 3.39%, p = 0.03) and 30 J/cm(2) (-10.90 +/- 1.97%, p = 0.01) affected significant inhibition. The effect of polychromatic LED therapy in oval full-thickness wound-healing in the diabetic model with the use of 5 and 10 J/cm(2) is promising. Further studies to determine optimum dosimetry and efficacy of LEDs are recommended.