Tag Archives: LED

Projecting beams of light from contact lenses courtesy of Princeton University (US)

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Princeton University’s 3D printed contact lenses with LED (light-emitting diodes) included are not meant for use by humans or other living beings but they are a flashy demonstration. From a Dec. 10, 2014 news item on phys.org,

As part of a project demonstrating new 3-D printing techniques, Princeton researchers have embedded tiny light-emitting diodes into a standard contact lens, allowing the device to project beams of colored light.

Michael McAlpine, the lead researcher, cautioned that the lens is not designed for actual use—for one, it requires an external power supply. Instead, he said the team created the device to demonstrate the ability to “3-D print” electronics into complex shapes and materials.

“This shows that we can use 3-D printing to create complex electronics including semiconductors,” said McAlpine, an assistant professor of mechanical and aerospace engineering. “We were able to 3-D print an entire device, in this case an LED.”

A Dec. 9, 2014 Princeton University news release by John Sullivan, which originated the news item, describes the 3D lens, the objectives for this project, and an earlier project involving a ‘bionic ear’ in more detail (Note: Links have been removed),

The hard contact lens is made of plastic. The researchers used tiny crystals, called quantum dots, to create the LEDs that generated the colored light. Different size dots can be used to generate various colors.

“We used the quantum dots [also known as nanoparticles] as an ink,” McAlpine said. “We were able to generate two different colors, orange and green.”

The contact lens is also part of an ongoing effort to use 3-D printing to assemble diverse, and often hard-to-combine, materials into functioning devices. In the recent past, a team of Princeton professors including McAlpine created a bionic ear out of living cells with an embedded antenna that could receive radio signals.

Yong Lin Kong, a researcher on both projects, said the bionic ear presented a different type of challenge.

“The main focus of the bionic ear project was to demonstrate the merger of electronics and biological materials,” said Kong, a graduate student in mechanical and aerospace engineering.

Kong, the lead author of the Oct. 31 [2014] article describing the current work in the journal Nano Letters, said that the contact lens project, on the other hand, involved the printing of active electronics using diverse materials. The materials were often mechanically, chemically or thermally incompatible — for example, using heat to shape one material could inadvertently destroy another material in close proximity. The team had to find ways to handle these incompatibilities and also had to develop new methods to print electronics, rather than use the techniques commonly used in the electronics industry.

“For example, it is not trivial to pattern a thin and uniform coating of nanoparticles and polymers without the involvement of conventional microfabrication techniques, yet the thickness and uniformity of the printed films are two of the critical parameters that determine the performance and yield of the printed active device,” Kong said.

To solve these interdisciplinary challenges, the researchers collaborated with Ian Tamargo, who graduated this year with a bachelor’s degree in chemistry; Hyoungsoo Kim, a postdoctoral research associate and fluid dynamics expert in the mechanical and aerospace engineering department; and Barry Rand, an assistant professor of electrical engineering and the Andlinger Center for Energy and the Environment.

McAlpine said that one of 3-D printing’s greatest strengths is its ability to create electronics in complex forms. Unlike traditional electronics manufacturing, which builds circuits in flat assemblies and then stacks them into three dimensions, 3-D printers can create vertical structures as easily as horizontal ones.

“In this case, we had a cube of LEDs,” he said. “Some of the wiring was vertical and some was horizontal.”

To conduct the research, the team built a new type of 3-D printer that McAlpine described as “somewhere between off-the-shelf and really fancy.” Dan Steingart, an assistant professor of mechanical and aerospace engineering and the Andlinger Center, helped design and build the new printer, which McAlpine estimated cost in the neighborhood of $20,000.

McAlpine said that he does not envision 3-D printing replacing traditional manufacturing in electronics any time soon; instead, they are complementary technologies with very different strengths. Traditional manufacturing, which uses lithography to create electronic components, is a fast and efficient way to make multiple copies with a very high reliability. Manufacturers are using 3-D printing, which is slow but easy to change and customize, to create molds and patterns for rapid prototyping.

Prime uses for 3-D printing are situations that demand flexibility and that need to be tailored to a specific use. For example, conventional manufacturing techniques are not practical for medical devices that need to be fit to a patient’s particular shape or devices that require the blending of unusual materials in customized ways.

“Trying to print a cellphone is probably not the way to go,” McAlpine said. “It is customization that gives the power to 3-D printing.”

In this case, the researchers were able to custom 3-D print electronics on a contact lens by first scanning the lens, and feeding the geometric information back into the printer. This allowed for conformal 3-D printing of an LED on the contact lens.

Here’s what the contact lens looks like,

Michael McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton, is leading a research team that uses 3-D printing to create complex electronics devices such as this light-emitting diode printed in a plastic contact lens. (Photos by Frank Wojciechowski)

Michael McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton, is leading a research team that uses 3-D printing to create complex electronics devices such as this light-emitting diode printed in a plastic contact lens. (Photos by Frank Wojciechowski)

Also, here’s a link to and a citation for the research paper,

3D Printed Quantum Dot Light-Emitting Diodes by Yong Lin Kong, Ian A. Tamargo, Hyoungsoo Kim, Blake N. Johnson, Maneesh K. Gupta, Tae-Wook Koh, Huai-An Chin, Daniel A. Steingart, Barry P. Rand, and Michael C. McAlpine. Nano Lett., 2014, 14 (12), pp 7017–7023 DOI: 10.1021/nl5033292 Publication Date (Web): October 31, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall.

I’m always a day behind for Dexter Johnson’s postings on the Nanoclast blog (located on the IEEE [institute of Electrical and Electronics Engineers]) so I didn’t see his Dec. 11, 2014 post about these 3Dprinted LED[embedded contact lenses until this morning (Dec. 12, 2014). In any event, I’m excerpting his very nice description of quantum dots,

The LED was made out of the somewhat exotic nanoparticles known as quantum dots. Quantum dots are a nanocrystal that have been fashioned out of semiconductor materials and possess distinct optoelectronic properties, most notably fluorescence, which makes them applicable in this case for the LEDs of the contact lens.

“We used the quantum dots [also known as nanoparticles] as an ink,” McAlpine said. “We were able to generate two different colors, orange and green.”

I encourage you to read Dexter’s post as he provides additional insights based on his long-standing membership within the nanotechnology community.

Lighting your way onto the internet with LiFi

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Chinese researchers have found a way to use lightbulbs instead of WiFi to access the internet, according to an Oct. 17, 2013 news item on Nanowerk,

Successful experiments by Chinese scientists have indicated the possibility of the country’s netizens getting online through signals sent by lightbulbs (LiFi), instead of WiFi.

Four computers under a one-watt LED lightbulb may connect to the Internet under the principle that light can be used as a carrier instead of traditional radio frequencies, as in WiFi, said Chi Nan, an information technology professor with Shanghai’s Fudan University, on Thursday [Oct. 17, 2013].

The Oct. 17, 2013 news release on Xinhua News (China’s official press agency), which originated the news item, describes the possibilities of ‘LiFi’,

A lightbulb with embedded microchips can produce data rates as fast as 150 megabits per second, which is speedier than the average broadband connection in China, said Chi, who leads a LiFi research team including scientists from the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences.

With LiFi cost-effective as well as efficient, netizens should be excited to view 10 sample LiFi kits that will be on display at the China International Industry Fair that will kick off on Nov. 5 [2013] in Shanghai.

The current wireless signal transmission equipment is expensive and low in efficiency, said Chi.

“As for cell phones, millions of base stations have been established around the world to strengthen the signal but most of the energy is consumed on their cooling systems,” she explained. “The energy utilization rate is only 5 percent.”

Compared with base stations, the number of lightbulbs that can be used is practically limitless. Meanwhile, Chinese people are replacing the old-fashioned incandescent bulbs with LED lightbulbs at a fast pace.

“Wherever there is an LED lightbulb, there is an Internet signal,” said Chi. “Turn off the light and there is no signal.”

However, there is still a long way to go to make LiFi a commercial success.

“If the light is blocked, then the signal will be cut off,” said Chi.

More importantly, according to the scientist, the development of a series of key related pieces of technology, including light communication controls as well as microchip design and manufacturing, is still in an experimental period.

The term LiFi was coined by Harald Haas from the University of Edinburgh in the UK and refers to a type of visible light communication technology that delivers a networked, mobile, high-speed communication solution in a similar manner as WiFi.

I was not able to find any academic papers about Chi’s work with LiFi but there is her academic page here. As for the fair where Chi’s work will be displayed. CIIF 2013 – The 15th China International Industry Fair 2013 is being held in Shanghai from Nov. 5 – 9, 2013.

Rare earths, China, and Nanosys

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There’s been some discussion recently about rare earths in the light of tensions between China and Japan. Here’s a brief description of rare earths for anyone who’s not certain what they are, from the Wikipedia essay on rare earths,

… rare earth elements or rare earth metals are a collection of seventeen chemical elements in the periodic table, namely scandium, yttrium, and the fifteen lanthanides.

Despite their name, rare earth elements (with the exception of the highly unstable promethium) are relatively plentiful in the Earth’s crust, with cerium being the 25th most abundant element at 68 parts per million (similar to copper). However, because of their geochemical properties, rare earth elements are not often found in concentrated and economically exploitable forms, generally called rare earth minerals. It was the very scarcity of these minerals (previously called “earths”) that led to the term “rare earth”

Here’s what started the tensions (from the NY Times article by Keith Bradsher),

Chinese customs officials abruptly halted the processing of paperwork for shipments bound for Japan on Sept. 21 [2010]. The shipments were halted during an acrimonious dispute over Japan’s detention of a Chinese fishing trawler that rammed two Japanese coast guard vessels two weeks earlier near islands long controlled by Japan but claimed by China.

Here’s why they’re so important,

Rare earths are vital to the production of a wide range of industrial products, including automobiles, glass, oil refining, computers, smartphones, wind turbines and flat-screen televisions. The military needs them for missiles, sonar systems and the range finders of tanks.

Here are some of the consequences of the ban,

Many factories in China assemble products that require high-tech components from Japan that use rare earths. Some of these factories, which employ large numbers of workers in China, have begun running low on components as Japanese suppliers ran short on some of the more obscure rare earths needed to manufacture them, two rare earth industry executives said.

Electronics industries have been affected, particularly camera manufacturers, leading to a desperate scramble for raw materials that has even included buying tons of obscure rare earth compounds from corporate stockpiles in Europe and airlifting them to Japan.

All 32 of the authorized rare earth exporters in China have refused to increase their shipments to other countries during the unannounced ban on shipments to Japan, making it difficult for Japanese traders to obtain supplies indirectly.

As a result of the blocked shipments, some rare earths now cost up to 10 times as much outside China as inside; the Chinese government has started a vigorous campaign to prevent this from leading to smuggling.

Brasher’s article is very interesting and I do recommend reading all of it.

There has been one other consequence to this concern over a dependency on China’s rare earths (excerpted from the Nov. 23, 2010 article by Ariel Schwartz on Fast Company),

There’s just one problem: The metals are only found in high concentrations in a few sites in China, the U.S., and Australia–and China has threatened to stop exporting its supply. But instead of expanding rare earth metal mines, what if we look for more sustainable replacements?

Enter Nanosys, a company that offers process-ready materials for the LED and energy-storage markets, among other things. Nanosys has been thinking about rare earth material shortages for years, which is why the company manufactures synthetic phosphors out of common materials–not the rare earth materials (i.e. yttrium) usually used in phosphors.

“We make a semiconductor phosphor that employs a nanomaterial called a quantum dot,” explains Nanosys CEO Jason Hartlove. “It’s made out of indium phosphide and phosphorous, and the synthesis process is all in the lab. There’s no heavy metal mining, no destructive mining practices.”

Nanosys’s QuantumRail LED backlighting device is made out of quantum dots, which can purportedly generate brighter and richer colors than their rare earth metal counterparts–all while delivering a higher efficiency and lower cost.

I don’t know how close they are to producing these quantum dots in industrial quantities but the appeal of a process that lessens dependency on resources that have to be mined and/or be used to apply political pressure is undeniable. If you’re interested, you can visit the Nanosys website here.

(They talk about ‘architected’ materials. I view that word with the same enthusiasm I have for ‘impactful’. These people should never be allowed to invent another word, ever again.)