New UV-LED technology could offer an exciting new way to clean water. Most common infectious diseases, which impact millions of people each year, are caused by bacteria and viruses that are either consumed through improperly filtered drinking water or by airborne contact. Even in developed Western countries, a long history of improper antibiotic use, coupled with little development of effective new antibiotics, is causing the emergence of "superbugs," resistant to all front-line treatment. Some scientists posit that deaths due to these superbugs may surpass AIDS in the US. Worse yet, hospitals, which were once a haven for the sick, are now one of the biggest sources of superbugs such as MRSA and Clostridium difficile, killing at least one hundred thousand people each year in the US. The development of effective, economical and mobile technology to kill common bacteria and viruses is, therefore, a pressing global urgency.

Exciting new research out of North Carolina State University might just make such technology a reality. Proposed as a tool for everything from water purification to sterilization of hospital equipment, a new energy-efficient LED device utilizes UV light to kill pathogens. Lead author Dr. Ramón Collazo is excited about the “development of robust and portable water-treatment technologies for use in developing countries, which would be more cost-effective, energy efficient and longer lasting.”

Prior attempts to exploit LED as a microbial agent have been hampered by the use of aluminum nitride (AIN) as a semiconductor in LEDs, which has the unfortunate effect of absorbing critical UV wavelengths, and therefore negating their microbial properties. The NCSU team, in concert with Japanese researchers, deduced that the wavelength absorption was not due to the AIN semiconductor itself, but rather trace carbon atoms present in the substrate. Removal of these atoms did not affect LED efficiency, however it did significantly improve passing UV light. Further development of AIN-based LED technology is being explored by the company HexaTech, Inc. as well as funding from the US government Materials Genome Initiative.

NC State researchers found that trace carbon atoms in the substrate of the aluminum nitride semiconductors block key wavelengths of UV light. Market analysts recently predicted that the UV-LED market would reach as high as $150 Million by 2016. Not surprisingly, the above research and development of UV antimicrobial technology is not alone in the marketplace. Partially funded by the Defense Advanced Research Project Agency (DARPA) and in conjunction with Army Research Laboratories (ARL), competing UV technology at the US firm Sensor Electronic Technology (SETi) has been developed by engineers that delivers an output of 9.8 mW, an eight percent wall-plug efficiency. SETi’s UV output, and increased efficiency, is credited to a different semiconductor -- instead of AIN, SETi uses sapphire substrates that result in better light extraction -- and the reduction of threading dislocation densities in the layers between the semiconductor and sapphire substrates. For their efforts with UV technology, SETi was recently rewarded with a prestigious Tibbetts Award for small business innovation research or technology transfer, presented at the White House.

Also throwing its ring in to the UV disinfectant race is United States company Aquionics, which launched an LED-based water disinfection module called the “Ultra Pearl.” Designed for low-flow applications requiring ultra-pure water, the Ultra Pearl will be marketed towards pharmaceutical and health care-related uses.

Innovation of water purification methods and devices in developing countries has been a longstanding goal, both for the academic/non-profit community as well as the corporate biotechnology sector. Advances in UV technology by public and for-profit sectors represent vast stepping-stones towards realizing that goal. Nevertheless, despite the effectiveness of ultraviolet germicidal irradiation (UVGI), one major drawback will necessitate further research and refinement. UV disinfection is most effective in treating high-clarity purified water, whereas water with a high degree of particulate matter -- in a third world unrefined well, for example -- allows microbes to get buried behind particles and remain impervious to UV rays. Furthermore, if water flow were too fast, it would potentially bypass UV rays before they’d had a chance to disinfect and kill microbes properly. Finally, taking into account that UV rays at certain wavelengths are harmful to human beings, scientists must ensure that machines designed to purify water on a large scale don’t result in any long-term exposure to humans.

The ability to efficiently, cheaply and rapidly remove microbes by exposure to UV rays will undoubtedly save millions of lives and improve millions more. Through government initiatives and the innovation of private biotechnology, hopefully the dream of clean water will soon be fulfilled.