We've told you how plastic can become fuel and form flexible batteries and transparent solar cells. Now, Wake Forest University scientists have created a new type of lighting made from thin layers of light-emitting polymer combined with nanomaterials that glow.
Based on alternating current (AC) field-induced polymer electroluminescent (FIPEL), the lighting device emits a soft, white light, unlike the harsh light from either fluorescents or LEDs. The light is similar to sunlight, and also flicker-free. The device itself is shatter-proof, avoiding broken glass and the hazardous mercury contained in compact fluorescent (CFL) bulbs.
Wake Forest University scientists have devised a shatterproof, white light, flicker-free lighting device based on field-induced polymer electroluminescent (FIPEL) technology. (Source: Wake Forest University)
The new lighting devices are also long-lasting, said David Carroll, professor of physics and director of the university's Center for Nanotechnology and Molecular Materials, in a press release. He owns one that has worked for about 10 years. The device has about the same efficiency as LEDs and is twice as efficient as CFLs. In addition to applications in office and home lighting, Carroll envisions the technology being used in large display lighting, such as signs on buses and subway cars, as well as store marquees.
The research team, which Carroll heads, made the lighting device from three layers of moldable, light-emitting polymer. Multi-walled carbon nanotubes (MWNTs) are dispersed in the active layer's polymer, sandwiched between two dielectric layers. The team described its work in an article in Organic Electronics.
According to the article:
An asymmetric device structure, using one dielectric layer, was used to study band alignment effects of carbon nanotubes in charge injection from a contact. The presence of MWNTs within the emissive layer facilitates effective internal charge generation in the symmetric devices, as would be expected if they acted as a charge source. The MWNTs effectively doped the polymer, modifying energy level alignment in the device and increasing field-induced polarization currents. Increase in light emission of five times is achieved in composite devices compared with the device without MWNTs.
The device is inexpensive to make, and the materials can be formed into many shapes and colors, from regular bulbs that fit household lamp and fixture sockets, to large 2-feet x 4-feet panels for office lighting. The team is working with a company to commercialize and manufacture the technology, and Carroll expects it to be available sometime this year.
I figured as much. I assumed I was seeing the 60hz flicker from the wall. I suppose it would be cheaper and last longer to not filter the signal. I imagine if the cap burst, the whole strand would be shot. Similar to the only series bulbs. One goes, the circuit is cut. I am sure a line conditioner is sold separate. In other words, a CAP in a box for $29.99.
A cd/m^2 is also known as a nit, which is also 1 lumen per meter squared per steridian. There are pi steridians in a hemisphere, which is the total solid angle of a lambertian flat surface source.
A typical power led is about 1 mm on a side, or 1e-6 meters squared, and in excess of 100 lumens at around 1 watt drive. This is 3e7 nits So one led with 1mm^2 area = 100 lumens (or more )
A reference I have says a candle flame is 0.01 cd/mm^2 which is 1E4 cd/m^2.
So this would suggest 20 cd/m^2 is much dimmer than a candle flame, and to get 100 lumens total even, the area would need to be more than a meter squared.
Hi Cabe, The LED Christmas light flickering is caused by using a simple DC power supply rectifier circuit. If there is no output capacitor to filter the ripple, the LEDs respond by flickering.
TommyH, I think you meant candela, not candle power. The latter is considered an obsolete unit of measurement. Today, this is measured via luminance or luminous intensity. Wikipedia has a good article on luminance.
It looks like this may possibly be a breakthrough, or possibly not. I remeber the electro-luminescent panels and devices that we had in the 1960's and wonder if it is a new implemantation of that technology. Those devices did provide a nice grale-free light, but not that much of it. I have no ideas about the relative efficiency, or lumens per watt. But the devices were very long-lived. I think that they were sort of expensive, as well. I have a couple of the inverter packages that were used by Chrysler for the EL instrument panels back in 1965, I think. They put out a very spikey waveform with a peak of almost 200V.
It would be interesting to find out about the performance of an actual prototype, as opposed to that of a single research sample device. That is the sort of information that would help to understand where this technology lies, on the development toward commercialization curve.
I'm betting the reason ARS Technica didn't get "performance numbers" is because they asked the wrong question. So far, AFAIK, this is a number of prototype devices, not a single actual bulb with wattage specs, which is what will be produced after commercialization efforts are completed. The details that are available can be found in the (free) journal article, which we provide a link to. They include varying luminance intensities.
There seems to be some confusion here regarding the difference between prototypes and working products, and the amount of time it requires to move from the first to the second. I made an earlier comment on this subject: "Maybe we're all used to Silicon Valley-style announcements of new technology for sale right now in high volumes, and not of the long R&D cycle behind that technology. In materials technology, especially energy-related, development can take a long time...The main researcher has had a single working device for a long time--but not a bulb, and, presumably, a very expensive device, and, I'd guess, one he's been tinkering with as a prototype."
It is interesting that rather than talk about candle power, the devices are described as less harsh than LED or florescent lights. A candle meets those criteria as well as a match, a glowing ember etc. Can anyone put this into terms of candle power per watt or some other real world measurement?
As energy efficiency becomes more and more a concern for makers of electronics devices, researchers are coming up with new ways to harvest energy from sound vibration, footsteps, and even electromagnetic fields in the air.
The government wants to study your brain, and DARPA wants to use similar information to give robots true autonomy beyond any artificial intelligence developed to date. Sound like science fiction? It's not.
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