Ultrathin Inorganic LEDs

There is now a new process under development to create ultrathin, ultrasmall inorganic light-emitting diodes (LEDs) and assembling them into large arrays, which offers new classes of lighting and display systems with interesting properties.

Applications for the arrays, which you can print onto flat or flexible substrates ranging from glass to plastic and rubber, include general illumination, high-resolution home theater displays, wearable health monitors, and biomedical imaging devices.

“Our goal is to marry some of the advantages of inorganic LED technology with the scalability, ease of processing, and resolution of organic LEDs,” said John Rogers, the Flory-Founder chair professor of Materials Science and Engineering at the University of Illinois.

Compared to organic LEDs, inorganic LEDs are brighter, more robust, and longer-lived. Organic LEDs, however, are attractive because you can form them on flexible substrates, in dense, interconnected arrays. The researchers’ new technology combines features of both.

“By printing large arrays of ultrathin, ultrasmall inorganic LEDs and interconnecting them using thin-film processing, we can create general lighting and high-resolution display systems that otherwise could not be built with the conventional ways that inorganic LEDs are made, manipulated, and assembled,” Rogers said.

To overcome requirements on device size and thickness associated with conventional wafer dicing, packaging, and wire bonding methods, researchers developed epitaxial growth techniques for creating LEDs with sizes up to 100 times smaller than usual. They also developed printing processes for assembling these devices into arrays on stiff, flexible, and stretchable substrates.

As part of the growth process, a sacrificial layer of material embeds beneath the LEDs. When fabrication is complete, a wet chemical etchent removes this layer, leaving the LEDs undercut from the wafer but still tethered at anchor points.

To create an array, a rubber stamp contacts the wafer surface at selected points, lifts off the LEDs at those points, and transfers them to the desired substrate.

“The stamping process provides a much faster alternative to the standard robotic ‘pick and place’ process that manipulates inorganic LEDs one at a time,” Rogers said. “The new approach can lift large numbers of small, thin LEDs from the wafer in one step, and then print them onto a substrate in another step.”

By shifting position and repeating the stamping process, LEDs can transfer to other locations on the same substrate. In this fashion, you can create large light panels and displays from small LEDs made in dense arrays on a single, comparatively small wafer. And, because the LEDs can be placed far apart and still provide sufficient light output, the panels and displays can be nearly transparent. The thin device geometries allow the use of thin-film processing methods, rather than wire bonding, for interconnects.

In addition to solid-state lighting, instrument panels, and display systems, the new method also allows for flexible and even stretchable sheets of printed LEDs, with potential use in the health-care industry.

“Wrapping a stretchable sheet of tiny LEDs around the human body offers interesting opportunities in biomedicine and biotechnology,” Rogers said, “including applications in health monitoring, diagnostics, and imaging.”

LED Backlighting

It is said that energy-saving flat-panel television sets are about to become common in shops, spawning a whole new range of technical words to understand in Berlin.

Most manufacturers believe the best way to reduce TV power consumption is to change the type of lamp at the back of the flat panel, as well as to devise clever ways to reduce wasted light output.

The newest liquid-crystal-display (LCD) television sets are to feature LED backlights instead of the cold cathode fluorescent lamps (CCFL) which have done the job in the past. LED stands for light- emitting diode.

That is where the confusion starts, because at the same time, the electronics industry has been trying, without much success, to develop TV-sized displays where the image itself is formed by a matrix of LEDs.

LED backlighting has got nothing to do with that technology: all it changes is the light source that shines through the LCD screen.

Word has been spreading for a decade that LED light bulbs are more efficient than fluorescent lamps, so it is no surprise that TV manufacturers are also turning to this new light source.

Philips, for example, claims an energy saving of 40 per cent on its televisions.

The different ways of configuring this new type of backlight are sure to set off more confusion.

The simplest way to deploy the LEDs is around the four edges of the screen and let the light diffuse across the back of the screen. This is cheaper, and salespeople will make a point of explaining that these ‘edge-lit’ displays are even thinner than their predecessors.

‘For the bigger screens, this requires about 500 LEDs,’ explains Peter Koch of LG Germany.

More expensive are the so-called direct LED backlights. Instead of being placed around the edges, these LED lamps are arrayed right across the back of the screen. Direct-LED backlighting is a smart idea because the intensity of the light can be dimmed behind dark parts of the image. This ‘local dimming’ creates deeper, more natural blacks.

‘If the image is of people under a night sky,’ all the LEDs behind the sky will be turned off so that it really seems dark,’ explains Sascha Lange of Toshiba Germany.

This matters, because LCD televisions are often thought to be a degree inferior when compared to plasma flat-panel televisions. The black on existing LCD screens is generally a dark grey, and colours generally seem washed out when viewed off-centre.

Over time, local dimming also helps to save electricity and keep the TV set cooler.

The new backlights generally use LEDs that give off white light, but there is a third variant, the so-called RGB backlight system, which uses a mixture of red green and blue LEDs.

This will only be offered in the most expensive sets, aimed at buyers who want the very best. In fact, television broadcasts do not demand such a subtle graduation of colours, but the difference will be visible while watching the highest-quality high-definition films from Blu-ray discs.

Energy Saving Star – LED Lighting

In your home, lighting may be 10 percent of your bill. But in an office building it’s probably 40 percent, and so if you reduce your lighting energy consumption by a large fraction, the savings will be huge,” said James Brodrick, who leads the DOE’s solid-state lighting program.

A fact sheet from Brodrick’s office says this about LEDs: “In the coming decade, they will become a key to affordable net-zero energy buildings, buildings that produce at least as much energy annually as they use from the grid.”

The technology is advancing quickly, and costs will continue to drop, Brodrick said. The DOE tests LEDs and sets performance and efficiency guidelines under its Energy Star program.

LEDs are directional lights, used in recessed lighting and under-counter lights, for example. They’re not yet available as bulbs that cast light all around and fit in ordinary sockets.

“There’s an enormous and exciting potential, but we have a long way to go before we see anything besides directional lighting,” said Jeffrey P. Harris, the vice president for programs at the Alliance to Save Energy, a nonprofit group that promotes energy efficiency.

Even so, LEDs already are used to light offices, hotels, restaurants and other businesses.

The DOE predicts that LEDs will have better performance capability than fluorescent lighting in the next few years, and that they’ll continue to improve after that. They’re now comparable with fluorescent fixtures in efficiency, and the DOE says its Energy Star LEDs last two to five times longer.

Cost is the biggest reason that LEDs aren’t used more widely, Brodrick said.

LEDs have other advantages: They can be dimmed, don’t emit heat, don’t contain mercury – unlike compact fluorescents – and can produce warm-toned light.

Home Depot, the world’s biggest retailer of light bulbs, is starting to stock LED bulbs this summer and plans to have 10 kinds by September, said Jorge Fernandez, who’s in charge of light bulb purchases for the company.

Philips is working on many kinds of LEDs, including one to replace a 40-watt incandescent bulb that’s scheduled to be available next year, she said.

Derrick Hall of RE/Construct Inc. in Asheville, N.C., said that residential customers weren’t asking for LEDs because of the high upfront cost. Still, he’s hearing of some nonresidential customers who are looking into LEDs for the energy savings.

LEDs are much better than other lighting options, Hall said. The quality of the light is “far superior,” they offer big energy savings and there’s no cost to society for dealing with mercury, he said. Mercury, a neurotoxin, is found in small amounts in compact fluorescent bulbs.

How to Choose the Right Light Bulb

Until recently, most of us have used the incandescent lighting, which renders the color of objects more closely to that of natural light, in our homes. Fluorescent light was harsh and cold and typically used in offices.

Light is categorized by its color rendering index, or CRI for short, and its color temperature.  CRI is how a light source, a bulb, causes the color of an object to appear to our eye and how well variations in color and shade are duplicated in comparison to natural light.

The CRI number is a rating from 0 to 100, the higher the CRI number the better the color. An incandescent bulb has a CRI of 100. Fluorescent lights can have CRIs of anywhere from 50% to 99%.

Color temperature is expressed on the Kelvin scale (K) is the color appearance of the bulb and the light it produces.

The color temperature of lamps makes them visually “warm,” “neutral” or “cool” light sources. The lower the temperature (2700-3000K) , the warmer the source, yellow-red colors. The higher the temperature(5000K) the cooler the source, green-blue color range.

How this all applies to us when we go to buy light bulbs at Home Depot is that  we generally want light that will  give us the best color rendering, a high CRI number, usually with a neutral or warm color temperature, a lower Kelvin number.

Originally these parameters’ were only met by incandescent lighting, but that is not the case anymore. The compact fluorescent bulbs available today have CRI numbers and light quality that closely matches that of incandescent bulbs. Although compact fluorescent light (CFL) bulbs tend to be more expensive they convert electricity into light much more efficiently than incandescent. The lower energy cost of the CFL can offset the higher cost of the bulb. Compared to incandescent bulbs,  fluorescent bulbs use less power for the same amount of light and usually last longer

An article in Wikipedia states that  ” In the United States, a compact fluorescent light  can save over $30 dollars in electricity costs over the bulb’s life time compared to an incandescent bulb and save 2,000 times its own weight in green house gasses. ”

Many compact fluorescents are designed to replace incandescent bulbs and can fit into most existing fixtures.

A problem with compact fluorescents bulbs is that they are made with a small amount of mercury. This mercury  requires that they be disposed through a hazardous waste disposal program, they cannot be put in the regular trash.

Another type of light is the LED. The LED appears to be the bulb of the future. Although expensive LED bulbs can produce light that is comparable to incandescent.

LED (Light Emitting Diode) last longer that compact fluorescents, they use less energy than traditional bulbs and potentially, compact fluorescents. LED lights are made in all sizes and shapes. LEDs do not contain mercury so their disposal is not a problem.

An article in the New York Times quotes Charles F. Jerabek, the president and chief executive of Osram Sylvania, a unit of Siemans as stating “In the US 78 percent of the public is completely unaware that traditional light bulbs will be phased out in 2012.”

As we all konw that light bulbs should be more energy efficient, and incandescent bulbs will be a thing of the past.

Night Vision LED Book Light

Introducing a LightWedge Night Vision LED Book Light, which is an innovative customized design of LightWedge Original Booklights specially made for sailors, astronomers and pilots to provide an easier reading experience without waking others that may be within eyesight of you.

The red LED light illuminates the pages uniformly and helps in reading charts and maps in total darkness. In fact this can be used by geeky bookworms too who love to read in the night. The red light is extremely soothing for the eyes and the light doesn’t really spread beyond the page and hurt the eyes of the reader or disturb other people around.

The LightWedge LED booklight are the true reading lights and are more useful than the usual table lamps. They are portable, battery operated and when placed on the pages they just uniformly illuminate the prints and make night reading a true pleasurable experience. Each is only $45.89, with different models and colors available.

This Night Vision innovation will be useful for sailors, astronomers and pilots who need to consult charts and maps while navigating in the dark. Red light doesn’t really illuminate the darkness around like the white light. It can be used along with Night Vision Goggles with which one can see far in to darkness.

One can really hide in the dark and read comfortably in night vision lights. And if one wants to read something on the sly no need to hide under the bed or blankets with torch lights or table lamps, use LightWedge Night Vision LED Bookcase instead!

Do You Want to Make Your Bath Time More Fun?

We have always marveled at the simplicity and the beauty of the new shower head, which uses LED lights to give it an extra charm and makes the cleaning up time more colorful and fun, especially great for kids.

I haven’t really seen anything like this, and I think it is quite amazing. Using this shower, bath time will never be dull again, whether you are 3 years old, or you are 80. There are four different colors that appear on the shower, illuminating the water.

These lights are not just really cool to look at, but also have a certain level of practicality associated with them. The color of the LED light changes with temperature, and so if you have really hot water coming out of the shower, the lights glow red,and the color automatically changes with any fluctuations in temperature, going through yellow and blue and finally green for really cold water. This really helps because you will no longer have to test the water temperature before you step into the shower, and you can adjust the water accordingly until you reach the color that you want to.

The best part is you don’t need any additional batteries to operate the lights, they are powered by the water pressure, and this makes it an eco-friendly option. The shower head is also just the right size, very easy to install (just unscrew your old shower head and replace it with this one) and very sturdy, having been made with ABS plastic. They fit on to the standard shower pipe size, and so they are suitable for almost every bathroom.

This is most definitely the perfect accessory to make bath time more romantic, or even to entice your kids into showering. It is said that its price is around $67, so I think it isn’t even too expensive to consider, right?

No Charging LED Timer Light

This looks kind of cool. Any idea if it will make a ticking sound. Sort of like an old fashion kitchen timer. This interesting LED light concept will surely go well with those looking to add a little mood lighting while staying eco-friendly. Designed by Jasper Hou, the Timer To Light device is powered using mechanical energy. That’s right, no batteries, so no charging. In a way, it works like a wind-up toy. In this case, the base is rotated to store energy, which can then be used to light up the LEDs while it slowly unwinds.

From the images, the Timer To Light concept comes in several pleasant hues, which should blend easily into any room in the house. While no details were given as to how long the light will last, we’re hoping the timer ratings at the base refer to minutes rather than seconds. Else we can only imagine the frantic and rather pointless exercise of cranking up the device for a few moments of ambient-light enjoyment.

Green Bulbs Green Traffic Light

According to a member of the Northeastern Pennsylvania Alliance, interest in energy-efficient traffic lights is brightening on Aug. 6.

Forty-three municipalities, including nine in Lackawanna County, have signed up to have incandescent traffic lights replaced with LED — light-emitting diode — bulbs, which require less energy to illuminate and don’t have to be changed as often, said Kurt Bauman, manager of the alliance’s energy assistance program.

“Incandescent bulbs go out more frequently,” he said. “LED bulbs are guaranteed for five years and expected to last 10 years.”

Throop is the latest municipality in the county to approve the switch. It has 17 traffic signals at two intersections — a total of 51 bulbs to be replaced.

Replacement work costs about $3,500 per intersection — 25 to 30 bulbs — including the price of the bulbs and installation, Mr. Bauman said.

Brightness is the most noticeable difference between LED and incandescent bulbs, Mr. Bauman said.

Drivers may also notice a small ring within the light itself, he said.

“They’re somewhat distinguishable,” he said.

LEDs got a trial run in Clarks Summit earlier this year. Mr. Bauman’s organization partially funded the purchase and installation of the lights at four intersections.

“We know that converting incandescent bulbs to LED bulbs offers energy savings,” he said. “We just wanted to make sure that the funding we provided the municipalities would be an incentive.”

A post-project energy audit estimated the town will save $3,600 this year.

The organization has applied for grant money to assist municipalities with the cost of replacing the lights. It would need about $1 million to fully finance projects in all interested municipalities. If necessary, municipalities have to sign a letter agreeing to pay matching funds toward the project.

LED Era Come Soon

As we all know that LED (Light Emitting Diode) bulbs which will consume even less power than the CFL bulbs and once the mass production of Light Emitting Diode (LED) bulbs will start, its cost will go down. Gradually the era of electric bulbs will come to an end and only CFL bulbs will exist then. This will go a long way in promoting the LED bulbs among the masses,” said Venugopal, a senior member of the Delhi Electricity Regulatory Commission, on Wednesday.

The occasion was the Second Capacity Building Programme, organised by the department of Industrial and Management Engineering of IIT, Kanpur. On the second day of the six-day long programme, Dr Anoop Singh of IIT-K, Venugopal, member of DERC and others were present.

Venugopal also explained that the entire focus is on to encourage the people of the country to save power instead of adopting a careless attitude towards it. Shutting down power switches when power is not required is something which people need to inculcate in themselves as a habit.

Giving an example about reduction of the load during the lunch hours in Delhi, Venugopal said, “At the time of lunch it has been observed that there is a reduction of 150 MW to 200 MW of load in the state of Delhi. This happens due to the fact that people in offices and at other commercial establishments shut down power. Such an exercise should be followed everywhere which will help in reducing the load.”

Dr Anoop Singh, said, “Power saved is power gained. Here in IIT-K we have street lights which are timer guided. The timer attached with the street light is set on a particular time as to when the street lamp should go off. The moment the clock strikes the set time, the street lamp goes off. This not only helps in saving power but also no human being is required to go from pole to pole for switching off these lamps.”

Additionaly, street lights can be put off with the help of the remote used in TVs and in other electrical devices.

Tiny Carrying LED Projector for Laptop

Do you want a big video picture but without the big bucks for a big screen? Here I introduce BenQ Joybee GP1 mini projector to you. The $500 1.4-pound pico projector uses a 20,000-hour LED lamp for illumination, and includes a USB port. Put your media (movies, photos, business presentations) on a thumb drive and you can leave your laptop at home.

The tiny unit comes with a carrying case, but you have to carry the separate, equally sized power supply by itself. Fortunately, the GP1 really can be set up without reading a manual. It took me about five minutes to connect the cords and figure out the commands on the wafer-sized remote.

You can connect a camcorder, DVD player, TV, video game console or — with an extra-cost dock — an iPod to the Joybee. But if you want to watch videos, you first must convert your files into the AVI format, using the included Mac and Windows software.

The company claims that the projector can create an image up to 80 inches in diameter, but don’t expect that size during the day. Even in a dimly lighted room, the weak light output meant that I had to put the unit quite close to the wall to see a bright-enough image.

As a pico projector, the Joybee lacks an optical zoom, which means you have to move the entire unit to change the picture size. That may not be practical in a business setting, but if you’re planning on watching a movie in your hotel room with all the lights out, it may not be a big deal. Once set up, the colors were well-saturated, with acceptable black levels.

The menus are intuitive and the remote works well, but the on-unit touch controls were erratic, often not responding to multiple hard presses and then jumping into action with a very light tap.

So it is a low-cost way to get a big picture in a dark room, won’t rely on this projector for your PowerPoint presentations.