Micro-Cavity Arrays - Lighting the Way to the Future
- Wednesday, 14 December 2011
A research team funded by the Air Force Office of Scientific Research has pioneered the use of micro-plasmas in a revolutionary approach to illumination, and doctors Gary Eden and Sung-Jin Park of the University of Illinois, Urbana-Champaign, have founded Eden Park Illumination, Inc. to bring this new lighting technology to the world.
Just as in a fluorescent light, a micro-cavity array (MCA) is energized by an applied voltage. By successfully confining plasma in parallel rows of micro-cavities within thin sheet materials, Eden and Park ultimately arrived at various implementations of micro-plasma arrays - some of which result in inexpensive, wafer-thin, and very flexible sheets of light.
The key to these light arrays are the micro-cavities which are formed within the flexible sheets. In one of the most important implementations, the one being developed by Eden Park Illumination, a sheet of aluminum foil is placed in an anodizing bath. By controlling the bath parameters, its temperature, and the time of anodizing, large arrays of micro-cavities can be formed with near optimum shape and with automatically placed interconnecting aluminum electrodes. The largest array thus far contains a quarter million luminous micro-cavities. Thin laminated films on the surface of the wafer contain the electrical power interconnects which feed the individual cavities. When A/C power is supplied through the almost invisible grid, the array bursts to life.
Many gases can be used to make the micro-plasma arrays. In Eden Park's commercialization processes, rare gases produce ultraviolet light, and specialty phosphors convert the UV into visible light, as in fluorescent lamps.
The largest arrays currently being produced are six inches square. These can be tiled together, in different colors if desired, to make larger arrays, and if desired, much larger arrays can be made, limited only by the size of the anodizing bath. Aluminum foil is used, with a thickness of 125 microns (5/1000ths of an inch). The cavities are then sealed in very thin sheets of glass resulting in an array that is one to two millimeters thick. The plasma arrays are ruggedized to a certain extent and have an ultimate thickness of about four millimeters, leaving you with a wafer that weighs less than 200 grams.
While the efficiency of the MCA does not quite measure up to that of LEDs, there is a positive side, that being a huge difference in thermal dissipation. MCAs generate far less heat and therefore do not require an aluminum heat sink as LEDs do, thus, MCAs not only run much cooler, but are much lighter as well.