Compact UV LED Lamp with Low Heat Emissions for Biological Research Applications

Selective Light Measurement in the Control of Reference LED Sources

This paper describes an original adaptive multispectral LED light source that utilizes miniature spectrometer to control its flux in real time. Current measurement of the flux spectrum is necessary in high-stability LED sources. In such cases, it is important the spectrometer work effectively with the system that controls the source and the whole system. Therefore, as important as flux stabilization is the integration of the integrating sphere-based design with the electronic module and power subsystem. Since the problem is interdisciplinary, the paper mainly focuses on presenting the solution of the flux measurement circuit. In particular, the proprietary way of operating the MEMS optical sensor as a real-time spectrometer was proposed. Then, the implementation of the sensor handling circuit, which determines the spectral measurements accuracy and thus the output flux quality, is described. Also presented is the custom method of coupling the analog part of the flux measurement path with the analog-to-digital conversion system and the control system based on the FPGA. The description of the conceptual solutions was supported by the results of simulation and laboratory tests at selected points of the measurement path. The presented concept allows to build adaptive LED light sources in the spectral range from 340 nm to 780 nm with adjustable spectrum and flux value, with electrical power up to 100 W, with adjustable flux value in the range of 100 dB, operating in constant current or pulsed mode.

Photostability studies of GarKS peptides for topical formulation development

There is a growing interest in the use of antimicrobial peptides (AMPs) as potent alternatives for conventional antibiotics, especially in chronic infected wounds. The development of a suitable topical formulation requires a thorough assessment of the photostability profiles of AMPs. In this study, we sought to investigate the photostability of novel Garvicin KS (GarKS; composed of three peptides GakA, GakB, and GakC) peptides either as an individual peptide or in combinations. The photostability of the aqueous peptide solution was determined using Suntest (indoor and outdoor conditions). Furthermore, the antimicrobial efficacy of the peptides was evaluated following UVA irradiations. Photodegradation of the peptides under indoor and outdoor conditions followed first-order kinetics. Individual peptides (GakA, GakB, and GakC) were more prone to photodegradation as compared to combination peptides (GakA+GakB, GakB+GakC, and GakA+GakC) both under indoor and outdoor conditions where the GakA+GakB combination was the most photostable. A combination of GakA+GakB+GakC enhanced photostability under indoor conditions but was reduced under outdoor conditions. A combination of three peptides with an antioxidant (glutathione) or superoxide/hydrogen peroxide scavenger (trehalose) enhanced the photostability of peptides with the highest stability achieved at a peptide:photostabilizer molar ratio of 1:0.8 for glutathione. A nominal increase in the MIC value for the peptide combinations as opposed to a larger increase for individual peptides further supports the photostability effects of combination peptides following UVA irradiations. These results suggest that the GakA+GakB or GakA+GakB+GakC combinations exhibited the highest photostability with excellent antimicrobial efficacy deemed suitable for the development of a potent AMP formulation for topical applications.

Lifetime Analysis of Commercial 3 W UV-A LED

The lifetime of ultraviolet high-power light-emitting diodes (UV HP-LEDs) is an open issue due to their high current density, high temperature, and UV radiation. This work presents a reliability study and failure analysis of three high-temperature accelerated life tests (ALTs) for 13,500 h with 3 W commercial UV LEDs of 365 nm at a nominal current in two working conditions: continuous mode and cycled mode (30 s on/30 s off). Arrhenius–Weibull parameters were evaluated, and an equation to evaluate the lifetime (B50) at any junction temperature and other relevant lifetime functions is presented. The Arrhenius activation energy was 0.13 eV for the continuous mode and 0.20 eV for the cycled mode. The lifetime at 50% survival and 30% loss of optical power as a failure definition, working at Ta = 40 °C with a multi-fin heat sink in natural convection, was over 4480 h for the continuous mode and 19,814 h for the cycled mode. The need to add forced convection for HP-LED arrays to achieve these high-reliability values is evidenced. The main source of degradation is the semiconductor device, and the second is the encapsulation silicone break.

Applications of Light-Emitting Diodes (LEDs) in Food Processing and Water Treatment

Light-emitting diode (LED) technology is an emerging nonthermal food processing technique that utilizes light energy with wavelengths ranging from 200 to 780 nm. Inactivation of bacteria, viruses, and fungi in water by LED treatment has been studied extensively. LED technology has also shown antimicrobial efficacy in food systems. This review provides an overview of recent studies of LED decontamination of water and food. LEDs produce an antibacterial effect by photodynamic inactivation due to photosensitization of light absorbing compounds in the presence of oxygen and DNA damage; however, such inactivation is dependent on the wavelength of light energy used. Commercial applications of LED treatment include air ventilation systems in office spaces, curing, medical applications, water treatment, and algaculture. As low penetration depth and high-intensity usage can challenge optimal LED treatment, optimization studies are required to select the right light wavelength for the application and to standardize measurements of light energy dosage.