Blue Light-emitting Diode Array Research Articles

Inexpensive bioprinting on a microscope using liquid crystal displays and visible light

Patterned photocrosslinking has several uses in the biofabrication of microstructurally complex tissue constructs, through both photolithography of scaffolds and photoconjugation of cell adhesive and instructive moieties. Often the polymers used are modified by methacrylation while photoactivation requires ultraviolet light. In contrast, this study aimed to design, build and evaluate a low-cost platform to place photocrosslink patterns into unmodified collagen and gelatin hydrogels using visible light and ruthenium-mediated tyrosine crosslinking in a way compatible with cell culture and inverted microscopes commonly used in biological laboratories. A photoprinting module was constructed above an inverted microscope sample stage to be confocal with the imaging system. The module consists of a blue light emitting diode array, light pipe, diffuser, microelectronically controlled liquid crystal display as photomask, and focusing objective. Resulting Ruthenium-mediated photocrosslink patterns were visible in unmodified collagen and gelatin hydrogels due to altered local polymer network density and optical contrast. Green fluorescent protein was conjugated in patterns to both gelatin and collagen gels, dependent on light exposure, intensity, and polymer network density. Pattern resolution varied from 2.0 ± 0.5 μm to 102 ± 33 μm (mean ± standard deviation) dependent on the focusing objective magnification and the pattern used (display pixel versus diode element). Further, photocrosslink patterns placed in collagen hydrogels and incubated without rinsing in serum-containing media swelled over 20–48 h, breaking the collagen network and forming ∼50 μm diameter holes. Fibroblasts cultured in photopatterned collagen hydrogels aligned and moved on and around crosslinked regions, consistent with durotaxis and contact guidance. The platform for photocrosslinking described in this study will impact several research fields, notably bioprinting of microstructurally and mechanically complex tissue constructs.

Power Controllable LED System with Increased Energy Efficiency Using Multi-Sensors for Plant Cultivation

In this paper, a power-controllable light emitting diode (LED) control system is proposed for plant cultivation. The proposed LED system measures environmental data, such as the distance between the plant and LED system using an infrared sensor and the ambient illuminance based on an illuminance sensor. Then, it converts the illuminance to the photosynthetic photon flux density (PPFD) for plant cultivation. It analyzes the relationship between the data and LED PPFD, and generates an optimal pulse width modulation (PWM) signal. Therefore, it controls the LED PPFD dynamically. The proposed LED system is also implemented in hardware, which consists of red and blue LED arrays with suitable wavelengths and a micro-controller. In the experimental results, the proposed LED system preserved the target PPFD regardless of the change of the distance and ambient PPFD. Additionally, the proposed LED system maximally reduced the power consumption of a conventional system by up to 68%.

Female ostracods respond to and intercept artificial conspecific male luminescent courtship displays

Some male cypridinid ostracods (ca. 2 mm) utilize luminescent secretions in the most unique and complex light displays yet described in marine environments. While swimming rapidly males secrete pulses of luminescence to attract females, but females do not reciprocate with light production. Females have been hypothesized to be attracted to and exhibit choice between these signals but this remained untested. Their small size and nighttime mating activity necessitated laboratory experiments that used light mimics of the male’s patterns in order to observe individual female behavior. In this study, we asked 2 simple questions: are females attracted to the light patterns that mimic conspecific male display patterns, and, if so, what do females actually do on detecting and responding to this signal pattern? Using a blue light-emitting diode array, we mimicked the male display of Photeros annecohenae in the lab and, in conjunction with infrared lighting and infrared cameras, we recorded individual behaviors of virgin females. Here, we provide direct evidence that females respond to the pulsed light mimic and approach the intermittent signal in such a way that they would cross closely above the path of an upwardly signaling male. In order to maximize her proximity to each pulse in the display, a responding female swims at a compensatory angle above the display to adjust her vector to intercept the male above each preceding pulse. These data support the hypothesis that luminescence is the initial signal used by males to attract receptive females in courting ostracods.

Planar Lighting System Using Array of Blue LEDs to Excite Yellow Remote Phosphor Film

This investigation demonstrates a novel light-emitting system with an array of blue light-emitting diodes (LEDs). Unlike a conventional lighting system that is constructed from white LEDs, the proposed planar lighting system uses blue LEDs to excite a YAG : Ce3+ yellow phosphor film remotely, yielding a high lumen efficiency with uniform and planar light-emission. The phosphor film herein acts as a wavelength converter and a light diffuser simultaneously. The optical properties of the proposed lighting system, angular color deviation and light-emitting uniformity, are studied. Eventually, a high lumen efficiency (73.0 lm/W) and thin lighting module (7.5 mm-thick) was demonstrated without the use of any conventional diffuser plate or light guiding plate (LGP). A low color deviation (Δu'v' = 0.025) and a high light-emitting uniformity (Uniformity = 82%) were achieved. Hence, the proposed lighting system exhibited superior optical performance using a compact module.

Novel optical method for background reduction in resonant photoacoustics

We report a new way of reducing the background originated by window absorption in resonant photoacoustics. The technique employs a secondary light source that is absorbed by the window but not by the gas sample. This auxiliary source is modulated 180 degrees apart from the one used to probe the gas. This way the window is heated almost uniformly during each cycle, thus lessening the associated background signal. We tested the scheme on a photoacoustic setup, conceived to measure NO(2), which is excited by an array of blue light-emitting diodes. Another array of near-infrared, light-emitting diodes served as the secondary light source. With the addition of this cancelling method, the detection limit was decreased to 4% of the previous reached without it.

Blue light-emitting diode-based, enhanced resonant excitation of longitudinal acoustic modes in a closed pipe with application to NO2

We present a new, very compact resonant photoacoustic system based on a simple closed pipe, transversally illuminated by an array of blue light-emitting diodes uniformly distributed along the tube to produce an acoustic signal from NO2–N2 samples. The illumination is modulated in a particular way as to produce amplification of the acoustic resonance corresponding to the second longitudinal mode. The linearity of the system for NO2 trace detection is studied. This arrangement provides a simple, compact, and cheap setup, useful for both measuring emissions from diesel engines and teaching photoacoustic spectroscopy in gases.