I’m starting to worry that I’m turning into an ostrich.

I’m territorial and ill-tempered. I’m fighting a strange desire to eat shiny objects. And when I get scared, I find myself hiding my face as though not seeing whatever is scaring me will make it go away. And this may or may not be related: I’m developing a strong aversion to light bulbs.

Image courtesy http://www.ostrichheadinsand.com/

A company called Nth Degree Tech may be able to help me out with that last problem. They’re seeking to replace light bulbs with their first commercial product, a two foot by four foot LED light sheet that’s flat and looks like a glowing piece of paper, which they plan to ship to customers for evaluation by the end of the year (Bullis). This is an exciting development, since it would allow lighting designers to get freaky with curved or unusually shaped light-emitting surfaces – at a price point comparable to the current cost of fluorescent light bulbs and fixtures.

Image courtesy Nth Degree Tech

To make their snazzy new lighting material, Nth Degree workers carve up “a wafer of gallium nitride to produce millions of tiny LEDs—one four-inch wafer yields about eight million of them. The LEDs are then mixed with resin and binders, and a standard screen printer is used to deposit the resulting ‘ink’ over a large surface” (Bullis).  They toss down a layer of silver ink for the back electrical contact, add a layer of phosphors that alter the color of the light emitted by the LEDs from blue to various shades of white, and then they slap on an insulating layer that prevents those pesky short circuits that can burn out the LEDs.

The front electrical contact is made with an ink containing invisibly small metal wires, which makes it transparent and allows light through the layer.  The transparent electrical contact ALONE could be the subject of an entire article, since it’s unspeakably awesome. Its awesomeness derives from the fact that it may eventually replace the brittle and often testy indium tin oxide (ITO) sheets that have been used in touch screens and electroluminescent assemblies in the past. ITO can be expensive, it can’t be printed and it’s not at all flexible – it deserves to be made redundant.

Image courtesy Nth Degree Tech

While printing with inks that are comprised of “tiny working LEDs produces much brighter light than depositing powders or thin films of electroluminescent material,” Nth Degree’s light sheets don’t match the best LEDs available today, which emit over 200 Lumens per watt.  The sheets are better than incandescent lights in terms of efficiency, emitting 20 lumens per watt, but they’re not as good as fluorescent lights just yet, which emit 80 lumens per watt (Bullis).

The new design won’t require heat sinks the way current conventional LEDs do because the lights are distributed evenly and in a thin layer, meaning that they do not get hot.  The downside is that the tiny LEDs need a pretty robust power source and as a result, Nth Degree’s first light fixture will be two inches thick despite the fact that the light-emitting surface is thin and flexible (Bullis).  I’m not letting that ruffle my feathers, however, since I’m betting that the whole assembly will get thinner over time.

WU XING:

Filed under FIRE because it lights up!

Cited:

Bullis, Kevin. “Lighting Sheets Made of Tiny LEDs” Technology Review Online. 10/28/11. Accessed 02/24/12. URL.

Every once in a while someone sends me a materials-related question and I get to sit at a local wing joint on a rainy day, my non-typing hand covered in piquant buffalo sauce and stringy, ranch-coated celery fragments, watching multiple football games simultaneously while happily dispensing advice on subjects about which I may or may not have any expertise … and it is glorious. In the interest of sharing knowledge and offering a forum for people with actual experience and/or information concerning the question to contribute what they know (which I hope you’ll do in the comments section) please allow me to present a recent query and answer for your infotainment:

Dear Alli,

We are students of product design and are interested in knowing about the methodology used in bending bamboo or lamboo for shaping.

Can you pls how this is done–is it by air pressure or water pressure or by direct heating?

Saroj
India

Hi Saroj,

Although it’s technically a grass, bamboo acts a lot like wood, in that it performs well in tension and it’s fibrous and fast-growing. And just as with its arboreal cousin, people bend bamboo in order to make furniture, walking canes, or perhaps they bend it for more complicated reasons such as in order to feel capable of imposing their will on the natural world. And from what I can tell, all of these bending operations, whether the object of your deformation is a piece of plywood or a length of bamboo, require the application of heat.

Image courtesy made-in-china.com

While I have seen people steam the bamboo or apply heated, wet rags then bend and clamp it into position once the material has absorbed enough moisture to become pliable, I think it’s also possible to just blast the stuff with a blowtorch. (I found a highly instructive video of a craftsman in Mexico bending bamboo using said tool, upon which I plan to base this advice). I’ll include the video but for those of you on YouTube restriction, here’s how it’s done:

First, the bamboo is rotated rapidly and heated with a blowtorch that the craftsman moves continuously, allowing him to apply heat to the entire length of the bamboo stalk without scorching it. He polishes the stalk with a rag then applies heat a second time, as though to lock in the polish.

Next, one end of the stalk gets sealed off and the hollow tube is filled with sand. I think the sand acts like a flexible internal reinforcing for the bamboo as it bends, preventing it from splitting, checking, or creasing as it bends. The sealed end is placed in a clamp, whereupon more fast-moving blowtorch heat gets applied as the craftsman bends the stalk into position.

After the bamboo has cooled, he is able to unstopper the ends and drain the sand out; and BAM! that craftsman has himself a perfectly curved piece of bamboo.

Lamboo, a material I have written about before, which is basically glu-lam made from bamboo, can also be bent, although I’d imagine that the process depends on the characteristics of the resin involved in the manufacture of the material, as well as how it’s configured etc.

There is also Bendywood, a sort of permanently flexible, slightly dehydrated wood product. I’m not sure if similar techniques could be applied to bamboo but it would be fun to try!

Saroj, I hope that this answers your question or that it at least provides some content for other informed people to disagree with or correct in the comments!

Sincerely,

Alli

WU XING:

I have filed this Q&A Special under WOOD because that is where I always file bamboo. HAH!

Yesterday I bent over in the attempt to tie the absurdly bright purple shoe laces on my almost offensively bright purple sneakers and made a startling discovery: I’m not as flexible as I used to be.  In fact, the overwhelming tightness of my hamstrings makes your standard British upper lip look positively floppy; and as I fired up my smartphone to schedule some emergency yoga I was reminded that I had yet to share an amazing new fully stretchable OLED display recently developed at the University of California, Los Angeles, a place where they know a thing or two about screens.

OLEDs or Organic Light-Emitting Diodes are great technology for screens primarily because they work without a backlight and can display deep black levels for high contrast.  OLED displays can be manufactured thinner and lighter than liquid crystal displays (LCDs) and “in low ambient light conditions such as dark rooms an OLED screen can achieve a higher contrast ratio than an LCD, whether the LCD uses either cold cathode fluorescent lamps or the more recently developed LED backlight. Due to their low thermal conductivity, they typically emit less light per area than inorganic LEDs” (Source: Wikipedia). What it all boils down to is that OLEDs are the bees knees. FACT.

Image courtesy wired.com

Once researchers saw how thin they could make OLEDs it was only a matter of time before people starting thinking about how to make them flexible. Stretchable electronics open up a world where video displays get rolled up and stuffed in your pocket, electronic sheets drape like cloth, electronics grow and shrink on command, and the mighty condor gets taken off the endangered species list.

Early attempts at stretchable electronics resulted in prototypes that connected rigid LEDs with stretchable material and others that bent but couldn’t stretch. The challenge researchers faced was how to ensure that the electrode could maintain connectivity while being deformed since many conductive materials can’t stretch nearly as far as one might like.  Enter the humble yet versatile carbon nanotube: it’s stretchable, conductive, appears transparent in thin layers, and it usually picks up the check after lunch dates.

The fly in the nanotube ointment, so to speak, is the fact that carbon nanotubes must be attached to a surface; the attachment can be tricky to pull off since when applied to a plastic backing nanotubes have a tendency to slide off or even slide past each other when the backing is stretched. To evict said proverbial fly from said proverbial ointment, the UCLA researchers created a carbon nanotube and polymer electrode layered on a stretchable, light-emitting plastic.

The researchers “coated carbon nanotubes onto a glass backing and added a liquid polymer that becomes solid yet stretchable when exposed to ultraviolet light. The polymer diffuses throughout the carbon nanotube network and dries to a flexible plastic that completely surrounds the network rather than just resting alongside it. Peeling the polymer-and-carbon-nanotube mix off of the glass yields a smooth, stretchable, transparent electrode” (Grifantini).  I imagine that the carbon nanotubes embedded in the plastic stretch at roughly the same rate, and that the plastic keeps to itself mostly and doesn’t interfere with the ability of the nanotubes to conduct electricity.

Image courtesy pcworld.com

The team sandwiched two layers of carbon nanotube electrode around another plastic that emits light when current runs through it.  Researchers obtained a laminator from a local office supply store to press the layered device together so that it could be handled safely in the presence of electric current.  As an aside, we did the same thing when we screen printed an electroluminescent lamp in Switzerland this summer and were hoping to not get electroshocked by the circuits. (More on that soon).  In contrast to our electroluminescent display, the flexible OLED created by the UCLA team can be stretched by as much as 45 percent while emitting a colored light.

Their prototype is a two-centimeter square that emits a one-centimeter square brilliant sky-blue light that stretches like silly putty until it loses conductivity due to being stretched too far or too many times (Grifantini).  The researchers also made a prototype using silver nano wires (which are more conductive than nanotubes) that exhibits similar stretching properties but is even more conductive.  Their layered approach is a great idea, not least because it’s easy to imagine how the process could be scaled up for production.  Now if only those scientists could help me with my hamstrings….

WU XING:

I have filed stretchable OLEDs under Water, Wood and Fire because they’re flexible, stretchy, and they light up.

Cited:

Grifantini, Kristina. “The First Fully Stretchable OLED.” Techreview.com 08/26/11. Accessed 10/05/11. URL.

Watch video: Stretchable OLED – Tech Review

And now, since you are probably wondering how on earth ebooks would be keeping me from spending long hours poolside engoldening myself, let me explain the difference between Kindle for iPhone and Kindle for … er … Kindle. Display screens on phones are typically LCD or OLED, and they don’t do well in sunlight. I’m not sure exactly why that is, but suffice it to say the screens are neither bold nor brilliant under typical pool-day conditions.  In contrast, e-readers like the Kindle use black and off-white electronic paper, which is purported to be easy on the eyes and performs much better in the great outdoors.

Image courtesy ebooknews.com

While it will take years for electronic ink manufacturers to develop color technology that matches LCD screens, E-Ink Holdings, the company that makes the electronic paper for Amazon’s Kindle e-reader, has been experimenting to extend their existing black and white display technology further. E-Ink Holdings recently announced that they can now print digital displays onto conventional cloth, as well as on “the rip-stop material Tyvek that’s used in yacht sails and toughened envelopes” (Eaton).  E-Ink’s new technology is ready for incorporation into products.

While it’s not as high-resolution as a fully pixelated e-ink screen that you’d see on an e-reader; rather, the cloth displays are segmented, ultra-thin, rugged, and flexible (SURF). The system works well in situations where it can flash on and off, but “presumably there’s not much stopping E-Ink from cleverly engineering it into a more complex array that emulates a basic 15-segment alphanumeric-capable display. And more precise pixels may be possible – making for a low-resolution black and white display on cloth” (Eaton). So yes, we are talking about wearable electronic display screens!

I can see this material being used so many ways, and in so many places in buildings and other structures – for instance, curtains and fabric-covered wall panels or ceilings that flash messages in emergency situations or display advertising. The SURF e-ink could also lend itself to t-shirts that alternate between the words “sexy” and “dance party” – which, based on a recent trip to Paris, I suspect would be wildly popular with 80% of the population of France. The possibilities are endless.

WU XING:

I have filed E-ink on Cloth under wood because it is flexible, and under fire because it can be controlled electronically.

Cited:

Eaton, Kit. “E-Ink on Cloth Raises the Terrible Prospect of T Shirt Ads.” FastCompany.com 05/04/11. Accessed 05/05/11. URL.

Image courtesy http://iopscience.iop.org

I’d long thought invisibility was reserved for fictional characters like Harry Potter, but it turns out researchers are actively trying to develop materials that create the effect.  So-called “metamaterials allow researchers to manipulate electromagnetic waves beyond the boundaries of what physics allows in natural materials. As well as promising better solar cells and high-resolution microscope lenses, metamaterials have also been used to create so-called invisibility cloaks, in which electromagnetic waves are bent around an object as if it simply weren’t there” (Cass).  Metamaterials must be constructed out of elements smaller than the wavelength of the electromagnetic radiation being manipulated, which means that “invisibility cloaks (and most metamaterial devices in general) only work with wavelengths longer than those found in visible light, such as radio and microwave frequencies. Metamaterials designed to work with optical wavelengths are built on rigid and fragile substrates, and as a result they’ve been confined to the lab” (Cass). Not too long ago, researchers at the University of St. Andrews created sheets of a flexible metamaterial that can manipulate visible light, taking a big step towards bringing metamaterials out of the lab and onto the market.

The new metamaterial is called “Metaflex” for obvious reasons, and it’s not exactly a piece of cake to manufacture.  First, researchers deposit a sacrificial layer atop a rigid substrate, to prevent subsequent layers from binding to it.  Then, a sheet of flexible, transparent plastic gets laid down and “a lithographic process, similar to that used to make silicon chips, creates a lattice of gold bars, each 100 to 200 nanometers long and 40 nanometers thick, on top of the polymer. (These bars act as ‘nanoantennas’ that interact with incoming electromagnetic waves.) The Metaflex material is then bathed in a chemical that releases the polymer from the layer below and from the rigid substrate” (Cass).  Variations in length and spacing of nanoantennas let Metaflex interact with different wavelengths of light.

Image courtesy http://iopscience.iop.org

The largest sheets researchers have produced so far are smaller than a postage stamp at five by eight millimeters, and they are only four micrometers thick.  Those samples may seem small when your goal is to cloak an entire person, but Metaflex is by far the largest sample of an optical metamaterial ever made.  Researchers believe that Metaflex can be scaled up for industrial production because it is flexible.  Being able to shape Metaflex into cylinders or spherical sections would allow for the creation of “curved super lenses that could manify objects so small that they currently can’t be seen with optical lenses due to diffraction effects” (Cass). ”  Metaflex can be fabricated flat and bent into shape.