LEDs Shed Light on New Applications — From Fighting Insomnia to Healing Wounds

LED use has dramatically increased as performance improves and costs decrease. Recently, nontraditional applications of LEDs delivering surprising quality-of-life improvements have grown in number. From applications in NASA's International Space Station to the functional lighting of white goods and a possible sleep solution, the continued use of LED lighting for new applications has been surprising in simplicity, yet increasingly impactful in results.

LED Applications from NASA

Some of the most exciting LED research has come out of NASA for applications related to plant growth, the healing of wounds and Seasonal Affective Disorder (SAD). At the Kennedy Space Center in Florida, for example, NASA's Advanced Exploration Systems (AES) Habitation program establishes new approaches to rapidly develop prototype systems, demonstrate capabilities and validate operational concepts for future human missions beyond Earth's orbit. One such project researched and tested the impacts of LED lights on plant growth for use in deep space missions. Within this harsh and demanding environment, LED lighting applications were harnessed to efficiently grow plants to feed to the crew and reprocess water.

Researchers studied the growth responses of red leaf lettuce and radish plants to broad-spectrum fluorescents with solid-state red and blue LED light sources and compared the results to what was grown under white fluorescents with green lighting. There was a marked difference in the yielded results. Red and blue LEDs, such as the Avago Technologies ASMT-AH00-ARS00, were found to deliver higher concentrations of anthocyanin, a powerful antioxidant combatting the effects of cosmic radiation.

On a smaller scale, hydroponic plants thrive in a variety of light spectra depending on the plant's stages of growth. While the blue light spectrum is best for young seedlings for the creation of strong stems, the red and orange spectra benefit the reproduction phase. LEDs simulate daylight, providing plants the wavelength necessary for growth and are operationally less expensive than traditional lamps, since they only consume a fraction of the energy.

In addition to their effects on plant cells, the same LEDs promote human skin, bone and muscle cell growth and are used to treat wounds in patients. Research conducted at the Medical College of Wisconsin has shown that cells exposed to near-infrared light therapy grow 150 to 200 percent faster than those not stimulated by the light. Multiple research projects sponsored by NASA are attempting to identify the way cells convert light to energy and also identify the wavelengths of light most effective at stimulating growth. Clinical trials have taken place at several U.S. and foreign hospitals, using this near-infrared light therapy to promote wound healing.

For many astronauts who spend any amount of time in space, SAD is a common problem that causes performance and memory challenges as well as physical illness. Aboard the noisy, high-pressure environment of the International Space Station (ISS), where astronauts are not exposed to the outdoor light that they may be used to, LED light therapy is making a difference. By 2016, NASA will outfit the U.S. section of the ISS with LEDs that simulate natural light rhythm: blue in the early hours, white for daytime, and red in the evening. NASA is spending $11.2 million on this project, which is expected to help mitigate the effects of seasonal - or in this case, out-of-this-world - depression symptoms.

The Molybdenite and Silicon Advantage

Not all applications using LEDs are as ostentatious as those from NASA, but they are nonetheless important. The materials used to create LEDs are evolving as well, as evidenced in the work performed in the Laboratory of Nanoscale Electronics and Structures (LANES). The laboratory has demonstrated the possibility of creating LEDs and solar cells using molybdenite, a mineral with a lubricating effect, which is being researched as a possible semiconductor replacement for silicon in transistors in electronic chips. Prototypes of diodes are created from a layer of molybdenite superposed on a layer of silicon. As the two elements each lose their energies, they transform into photons. Whereas other semiconductors transform the energy into heat, molybdenite uniquely transforms it into light, which can then produce electricity.

Tests indicate an efficiency of greater than 4 percent when molybdenite and silicon work in tandem. Molybdenite is efficient in visible wavelengths of the spectrum, and silicon is in the infrared range. Together, they cover the largest possible combined spectral range. Research continues toward the building of electroluminescent diodes and bulbs. Possible results could include reducing the dissipation of energy in such electronic devices as microprocessors. In addition, copper wires now used for transmitting data could be replaced with light emitters.

Glass Shelving and Embedded LEDs

Harnessing the power of LEDs has also spread to several interesting and commercially viable applications. LED footprint advances are resulting in a greater number of applications. For example, the low-profile rectangular shape of OSRAM's Synios E4014 LED enables light to be injected into light guides. The mid-power LEDs provide a uniform distribution of light. When integrated in the glass shelving of white goods, car interior lighting, and bus and van strip lighting, they lend a dramatic product differentiation in addition to the functional benefit of spreading light evenly throughout the application.

The Insomnia Antidote?

The warmth of sleep-inducing sunsets is being mimicked by LEDs without blue hues, and this technology is now available for home use by the sleep deprived. As a result of the color generated, the bulb avoids suppressing melatonin, which is necessary for a good night's sleep. Some of these sunset LEDs boast a dimming capability that works with existing dimmers, enabling the gradual dimming of the bulb in a way that simulates the average length of a sunset, just less than 40 minutes.

Research continues into amazing LED applications that are a far cry from typical LED light bulb replacement, providing not only a bright group of solutions, but those that potentially have far-reaching and dramatic effects in health, food production and the human condition. As cost continues to decline and performance skyrockets, it will be fascinating to watch LED technology further explode in use and benefit.

Written By: Carolyn Mathas

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