MIT Just Created Living Plants That Glow Like A Lamp, And Could Grow Glowing Trees To Replace Streetlights

Roads of the future could be lit by glowing trees instead of streetlamps, thanks to a breakthrough in creating bioluminescent plants. Experts injected specialized nanoparticles into the leaves of a watercress plant, which caused it to give off a dim light for nearly four hours. This could solve lots of problems.

The chemical involved, which produced enough light to read a book by, is the same as is used by fireflies to create their characteristic shine. To create their glowing plants, engineers from the Massachusetts Institute of Technology (MIT) turned to an enzyme called luciferase. Luciferase acts on a molecule called luciferin, causing it to emit light.

 

Roads of the future could be lit by glowing trees instead of streetlamps, thanks to a breakthrough in creating bioluminescent plants. Experts created a watercress plant which caused it to glow for nearly four hours and gave off enough light to illuminate this book

Another molecule called Co-enzyme A helps the process along by removing a reaction byproduct that can inhibit luciferase activity. The MIT team packaged each of these components into a different type of nanoparticle carrier.

The nanoparticles help them to get to the right part of the plant and also prevent them from building to concentrations that could be toxic to the plants. The result was a watercress plant that functioned like a desk lamp.

Researchers believe with further tweaking, the technology could also be used to provide lights bright enough to illuminate a workspace or even an entire street, as well as low-intensity indoor lighting. 

Michael Strano, professor of chemical engineering at MIT and the senior author of the study, said: 'The vision is to make a plant that will function as a desk lamp — a lamp that you don't have to plug in. The light is ultimately powered by the energy metabolism of the plant itself. Our work very seriously opens up the doorway to streetlamps that are nothing but treated trees, and to indirect lighting around homes.'

Luciferases make up a class of oxidative enzymes found in several species that enable them to 'bioluminesce', or emit light. Fireflies are able to emit light via a chemical reaction.

In the chemical reaction luciferin is converted to oxyluciferin by the luciferase enzyme. Some of the energy released by this reaction is in the form of light. The reaction is highly efficient, meaning nearly all the energy put into the reaction is rapidly converted to light.

Lighting accounts for around 20 per cent of worldwide energy consumption, so replacing them with naturally bioluminescent plants would represent a significant cut to CO2 emissions. The researchers’ early efforts at the start of the project yielded plants that could glow for about 45 minutes, which they have since improved to 3.5 hours.

The light generated by one ten centimetre (four inch) watercress seedling is currently about one-thousandth of the amount needed to properly read by, but it was enough to illuminate the words on a page of John Milton's Paradise Lost.

The MIT team believes it can boost the light emitted, as well as the duration of light, by further optimising the concentration and release rates of the chemical components. For future versions of this technology, the team hopes to develop a way to paint or spray the nanoparticles onto plant leaves, which could make it possible to transform trees and other large plants into light sources. 

The researchers have also demonstrated that they can turn the light off by adding nanoparticles carrying a luciferase inhibitor. This could enable them to eventually create plants that shut off their light emission in response to environmental conditions such as sunlight, they say.

The full findings of the study were published in the American Chemical Society journal Nano Letters.

ORIGINAL: The Space Academy
December 18, 2017

Carbon Nanotube Transistors Finally Outperform Silicon

Photo: Stephanie Precourt/UW-Madison College of Engineering

Back in the 1990s, observers predicted that the single-walled carbon nanotube (SWCNT) would be the nanomaterial that pushed silicon aside and created a post-CMOS world where Moore’s Law could continue its march towards ever=smaller chip dimensions. All of that hope was swallowed up by inconsistencies between semiconducting and metallic SWCNTs and the vexing issue of trying to get them all to align on a wafer.

The introduction of graphene seemed to take the final bit of luster off of carbon nanotubes’ shine, but the material, which researchers have been using to make transistors for over 20 years, has experienced a renaissance of late.

Now, researchers at the University of Wisconsin-Madison (UW-Madison) have given SWCNTs a new boost in their resurgence by using them to make a transistor that outperforms state-of-the-art silicon transistors.

“This achievement has been a dream of nanotechnology for the last 20 years,” said Michael Arnold, a professor at UW-Madison, in a press release. “Making carbon nanotube transistors that are better than silicon transistors is a big milestone,” Arnold added. “[It’s] a critical advance toward exploiting carbon nanotubes in logic, high-speed communications, and other semiconductor electronics technologies.”

In research described in the journal Science Advances, the UW-Madison researchers were able to achieve a current that is 1.9 times as fast as that seen in silicon transistors. The measure of how rapidly the current that can travel through the channel between a transistor’s source and drain determines how fast the circuit is. The more current there is, the more quickly the gate of the next device in the circuit can be charged .

The key to getting the nanotubes to create such a fast transistor was a new process that employs polymers to sort between the metallic and semiconducting SWCNTs to create an ultra-high purity of solution.

“We’ve identified specific conditions in which you can get rid of nearly all metallic nanotubes, [leaving] less than 0.01 percent metallic nanotubes [in a sample],” said Arnold.

The researchers had already tackled the problem of aligning and placing the nanotubes on a wafer two years ago when they developed a process they dubbed “floating evaporative self-assembly.” That technique uses a hydrophobic substrate and partially submerges it in water. Then the SWCNTs are deposited on its surface and the substrate removed vertically from the water.

“In our research, we’ve shown that we can simultaneously overcome all of these challenges of working with nanotubes, and that has allowed us to create these groundbreaking carbon nanotube transistors that surpass silicon and gallium arsenide transistors,” said Arnold.

In the video below, Arnold provides a little primer on SWCNTs and what his group’s research with them could mean to the future of electronics.

In continuing research, the UW-Madison team will be aiming to replicate the manufacturability of silicon transistors. To date, they have managed to scale their alignment and deposition process to 1-inch-by-1-inch wafers; the longer-term goal is to bring this up to commercial scales.

Arnold added: “There has been a lot of hype about carbon nanotubes that hasn’t been realized, and that has kind of soured many people’s outlook. But we think the hype is deserved. It has just taken decades of work for the materials science to catch up and allow us to effectively harness these materials.”

ORIGINAL: IEEE

By Dexter Johnson

6 Sep 2016

Nanorods could harvest water in dry climates

The accidental discovery holds on to water until you don't need it.

S. Nune et al/PNNL, Flickr

Sometimes it's the accidental discoveries that make the biggest impact. Researchers at Pacific Northwest National Laboratory have learned that carbon-rich nanorods created in a botched experiment might be ideal for harvesting water. When there's relatively low humidity (below 50 percent), the rods trap water inside their gaps; if it's any more humid, however, they promptly expel that water as vapor. It's a very unusual trait that's likely caused by water condensing into a "bridge" in the nanorods, whose surface tension forces them to close and eventually kick the water out.

If scientists can refine the shape of these nanorods and get them to spray water on a consistent basis (only 10 to 20 percent do that right now), the implications are huge. They'd be ideal for harvesting and purifying water in dry climates -- you could gather ambient moisture until there's enough to drink. Alternately, you could use it for anti-sweat clothing that soaks up your perspiration and spits it outside. All told, you'd have direct control over just when and how you get water.

Via: Gizmag

Source: PNNL

ORIGINAL: Engadget

Jon Fingas , @jonfingas

06.14.16

From Living Computers to Nano-Robots: How We’re Taking DNA Beyond Genetics

DNA is one of the most amazing molecules in nature, providing a way to carry the instructions needed to create almost any life form on Earth in a microscopic package. Now scientists are finding ways to push DNA even further, using it not just to store information but to create physical components in a range of biological machines.

Deoxyribonucleic acid or “DNA” carries the genetic information that we, and all living organisms, use to function. It typically comes in the form of the famous double-helix shape, made up of two single-stranded DNA molecules folded into a spiral. Each of these is made up of a series of four different types of molecular component: adenine (A), guanine (G), thymine (T), and cytosine (C).

Genes are made up from different sequences of these building block components, and the order in which they appear in a strand of DNA is what encodes genetic information. But by precisely designing different A, G, T and C sequences, scientists have recently been able to develop new ways of folding DNA into different origami shapes, beyond the conventional double helix.

This approach has opened up new possibilities of using DNA beyond its genetic and biological purpose, turning it into a Lego-like material for building objects that are just a few billionths of a meter in diameter (nanoscale). DNA-based materials are now being used for a variety of applications, ranging from templates for electronic nano-devices, to ways of precisely carrying drugs to diseased cells.

DNA-based nanothermometers

Designing electronic devices that are just nanometers in size opens up all sorts of possible applications but makes it harder to spot defects. As a way of dealing with this, researchers at the University of Montreal have used DNA to create ultrasensitive nanoscale thermometers that could help find minuscule hotspots in nanodevices (which would indicate a defect). They could also be used to monitor the temperature inside living cells.

The nanothermometers are made using loops of DNA that act as switches, folding or unfolding in response to temperature changes. This movement can be detected by attaching optical probes to the DNA. The researchers now want to build these nanothermometers into larger DNA devices that can work inside the human body.

Biological nanorobots

Researchers at Harvard Medical School have used DNA to design and build a nanosized robot that acts as a drug delivery vehicle to target specific cells. The nanorobot comes in the form of an open barrel made of DNA, whose two halves are connected by a hinge held shut by special DNA handles. These handles can recognize combinations of specific proteins present on the surface of cells, including ones associated with diseases.

When the robot comes into contact with the right cells, it opens the container and delivers its cargo. When applied to a mixture of healthy and cancerous human blood cells, these robots showed the ability to target and kill half of the cancer cells, while the healthy cells were left unharmed.

DNA barrel. Image credit: Campbell Strong, Shawn Douglas, and Gaël McGill.

Bio-computers in living animals

Because DNA structures can act as switches, moving from one position to another and back again, they can be used to perform the logical operations that make computer calculations possible. Researchers at Harvard and Bar-Ilan University in Israel have used this principle to build different nanoscale robots that can interact with each other, using their DNA switches to react to and produce different signals.

What’s more, the scientists implanted the robots into a living animal, in this instance a cockroach. This allowed them to develop a novel type of biological computer that can control the delivery of therapeutic molecules inside the cockroach by switching elements of their structure “on” or “off”. A trial of these DNA nanorobots is now scheduled to take place in humans.

Light-harvesting antennas

As well as creating minuscule machines, DNA can provide a way for us to copy natural processes at the nanoscale. For example, nature can capture energy from the sun using photosynthesis to convert light into chemical energy, which acts as fuel for plants and other organisms (and the animals that eat them). Researchers at Arizona State University and the University of British Columbia have now built a three-arm DNA structure that can capture and transfer light that mimics this process.

Photosynthesis occurs in living organisms thanks to tiny antennas made up of a large number of pigment molecules at specific orientations and distances from each other, which are able to absorb visible light. The artificial DNA-based structures act as similar antennas, controlling the position of specific dye molecules that absorb the light energy and channel it to a reaction centre where it is converted into chemical energy. This work could pave the way for devices capable of more efficiently using the most abundant source of energy we have at our disposal: sunlight.

So what’s next for DNA nanotechnology? It is hard to know but, with DNA, nature has given us a very versatile tool. It is now up to us to make the best use of it.

ORIGINAL: Singularity Hub

By MATTEO PALMA

ON JUN 07, 2016

Meet the Nanomachines That Could Drive a Medical Revolution

A group of physicists recently built the smallest engine ever created from just a single atom. Like any other engine it converts heat energy into movement — but it does so on a smaller scale than ever seen before. The atom is trapped in a cone of electromagnetic energy and lasers are used to heat it up and cool it down, which causes the atom to move back and forth in the cone like an engine piston.

The scientists from the University of Mainz in Germany who are behind the invention don’t have a particular use in mind for the engine. But it’s a good illustration of how we are increasingly able to replicate the everyday machines we rely on at a tiny scale. This is opening the way for some exciting possibilities in the future, particularly in the use of nanorobots in medicine, that could be sent into the body to release targeted drugs or even fight diseases such as cancer.

Nanotechnology deals with ultra-small objects equivalent to one billionth of a meter in size, which sounds an impossibly tiny scale at which to build machines. But size is relative to how close you are to an object. We can’t see things at the nanoscale with the naked eye, just as we can’t see the outer planets of the solar system. Yet if we zoom in — with a telescope for the planets or a powerful electron microscope for nano-objects — then we change the frame of reference and things look very different.

However, even after getting a closer look, we still can’t build machines at the nanoscale using conventional engineering tools. While regular machines, such as the internal combustion engines in most cars, operate according to the rules of physics laid out by Isaac Newton, things at the nanoscale follow the more complex laws of quantum mechanics. So we need different tools that take into account the quantum world in order to manipulate atoms and molecules in a way that uses them as building blocks for nanomachines. Here are four more tiny machines that could have a big impact.

1- Graphene engine for nanorobots

Researchers from Singapore have recently demonstrated a simple but nano-sized engine made from a highly elastic piece of graphene. Graphene is a two-dimensional sheet of carbon atoms that has exceptional mechanical strength. Inserting some chlorine and fluorine molecules into the graphene lattice and firing a laser at it causes the sheet to expand. Rapidly turning the laser on and off makes the graphene pump back and forth like the piston in an internal combustion engine.

The researchers think the graphene nano-engine could be used to power tiny robots, for example to attack cancer cells in the body. Or it could be used in a so-called “lab-on-a-chip” — a device that shrinks the functions of a chemistry lab into tiny package that can be used for rapid blood tests, among other things.

2- Frictionless nano-rotor

Molecular motor.
Image credit: Palma, C.-A.; Kühne, D.; Klappenberger, F.; Barth, J.V.; Technische Universität München

Molecular motor. Image credit: Palma, C.-A.; Kühne, D.; Klappenberger, F.; Barth, J.V.; Technische Universität München

The rotors that produce movement in machines such as aircraft engines and fans all usually suffer from friction, which limits their performance. Nanotechnology can be used to create a motor from a single molecule, which can rotate without any friction. Normal rotors interact with the air according to Newton’s laws as they spin round and so experience friction. But, at the nanoscale, molecular rotors follow quantum law, meaning they don’t interact with the air in the same way and so friction doesn’t affect their performance.

Nature has actually already shown us that molecular motors are possible. Certain proteins can travel along a surface using a rotating mechanism that create movement from chemical energy. These motor proteins are what cause cells to contract and so are responsible for our muscle movements.

Researchers from Germany recently reported creating a molecular rotor by placing moving molecules inside a tiny hexagonal hole known as a nanopore in a thin piece of silver. The position and movement of the molecules meant they began to rotate around the hole like a rotor. Again, this form of nano-engine could be used to power a tiny robot around the body.

3- Controllable nano-rockets

A rocket is the fastest man-made vehicle that can freely travel across the universe. Several groups of researchers have recently constructed a high-speed, remote-controlled nanoscale version of a rocket by combining nanoparticles with biological molecules.

In one case, the body of the rocket was made from a polystyrene bead covered in gold and chromium. This was attached to multiple “catalytic engine” molecules using strands of DNA. When placed in a solution of hydrogen peroxide, the engine molecules caused a chemical reaction that produced oxygen bubbles, forcing the rocket to move in the opposite direction. Shining a beam of ultra-violet light on one side of the rocket causes the DNA to break apart, detaching the engines and changing the rocket’s direction of travel. The researchers hope to develop the rocket so it can be used in any environment, for example to deliver drugs to a target area of the body.

4- Magnetic nano-vehicles for carrying drugs

Magnetic nanoparticles. Image credit: Tapas Sen, author provided

My own research group is among those working on a simpler way to carry drugs through the body that is already being explored with magnetic nanoparticles. Drugs are injected into a magnetic shell structure that can expand in the presence of heat or light. This means that, once inserted into the body, they can be guided to the target area using magnets and then activated to expand and release their drug.

The technology is also being studied for medical imaging. Creating the nanoparticles to gather in certain tissues and then scanning the body with a magnetic resonance imaging (MRI) could help highlight problems such as diabetes.

Tapas Sen, Reader in Nanomaterials Chemistry, University of Central Lancashire

This article was originally published on The Conversation. Read the original article.

ORIGINAL: Singularity Hub

BY TAPAS SEN

ON APR 21, 2016

Acoustic tweezers manipulate cells with sound waves

An illustration of the surface acoustic wave generators, with the generated 3-D trapping nodes. The inset indicates a single particle within a 3-D trapping node, which can be manipulated independently along x, y, or z axes.

Technique could enable 3-D printing of cellular structures for tissue engineering.

Engineers at MIT, Penn State University, and Carnegie Mellon University have devised a way to manipulate cells in three dimensions using sound waves. These “acoustic tweezers” could make possible 3-D printing of cell structures for tissue engineering and other applications, the researchers say.

Designing tissue implants that can be used to treat human disease requires precisely recreating the natural tissue architecture, but so far it has proven difficult to develop a single method that can achieve that while keeping cells viable and functional.

“The results presented in this paper provide a unique pathway to manipulate biological cells accurately and in three dimensions, without the need for any invasive contact, tagging, or biochemical labeling,” says Subra Suresh, president of Carnegie Mellon and former dean of engineering at MIT. “This approach could lead to new possibilities for research and applications in such areas as regenerative medicine, neuroscience, tissue engineering, biomanufacturing, and cancer metastasis.”

Suresh, Ming Dao, a principal research scientist in MIT’s Department of Materials Science and Engineering, and Tony Jun Huang, a professor of engineering science and mechanics at Penn State, are senior authors of a paper describing the device, published the week of Jan. 25. in the Proceedings of the National Academy of Sciences.

The paper’s lead author is Penn State graduate student Feng Guo. The team also includes Penn State researchers Zhangming Mao, Yuchao Chen, James Lata, Peng Li, Liqiang Ren, Jiayang Liu, Zhiwei Xie, and Jian Yang.

3-D control

The new acoustic tweezers are based on a microfluidic device that the researchers previously developed to manipulate cells in two dimensions. This device produces two acoustic standing waves, which are waves with a constant height. Where the two waves meet, they create a “pressure node” that can trap single cells. By altering the wavelength and another wave property known as the phase, the researchers can move the node and the cell trapped within it.

The research team previously used a similar approach to separate cancer cells from healthy cells, which could be useful for detecting rare tumor cells in a patient’s bloodstream and predicting whether the tumor will spread.

In the new study, the researchers added a third dimension of control: Once the cells are trapped in a horizontal plane, they can be moved up and down by altering the acoustic waves’ power, that is, the rate at which sound energy is emitted. Boosting the power allows the researchers to lift the cells from the surface in a type of “acoustic levitation,” then place them in a specific location, Dao says.

The researchers also developed equations that allow them to accurately predict how changes in the wavelength, phase, and acoustic power will affect cells’ positions.

“We now have a good idea of what to expect and how to control the 3-D positioning of the acoustic waves and the pressure nodes, enabling validation of the method as well as system optimization,” Dao says.

“Innovative approach”

In this study, the researchers demonstrated their device on polystyrene particles as well as mouse fibroblast cells. They were able to move the cells, one at a time, into specific positions on a surface and create patterns. They could also stack cells on top of each other.

“This is an exceptionally innovative approach of manipulating particles and single cells in 3-D in fluids,” says Taher Saif, a professor of mechanical science and engineering at the University of Illinois at Urbana-Champaign, who was not part of the research team. “Since acoustic energy is used for this manipulation, the approach is noninvasive and the cells maintain their viability. Overall, the method presented will be of significant interest for a broad community, from biologists to bioengineers.”

The researchers have filed for a patent on the technology and plan to continue developing it for tissue engineering and other applications.

ORIGINAL: MIT News

Anne Trafton | MIT News Office 

January 25, 2016

Forward to the Future: Visions of 2045

DARPA asked the world and our own researchers what technologies they expect to see 30 years from now—and received insightful, sometimes funny predictions

Today—October 21, 2015—is famous in popular culture as the date 30 years in the future when Marty McFly and Doc Brown arrive in their time-traveling DeLorean in the movie “Back to the Future Part II.” The film got some things right about 2015, including in-home videoconferencing and devices that recognize people by their voices and fingerprints. But it also predicted trunk-sized fusion reactors, hoverboards and flying cars—game-changing technologies that, despite the advances we’ve seen in so many fields over the past three decades, still exist only in our imaginations.

A big part of DARPA’s mission is to envision the future and make the impossible possible. So ten days ago, as the “Back to the Future” day approached, we turned to social media and asked the world to predict: What technologies might actually surround us 30 years from now? We pointed people to presentations from DARPA’s Future Technologies Forum, held last month in St. Louis, for inspiration and a reality check before submitting their predictions.

Well, you rose to the challenge and the results are in. So in honor of Marty and Doc (little known fact: he is a DARPA alum) and all of the world’s innovators past and future, we present here some highlights from your responses, in roughly descending order by number of mentions for each class of futuristic capability:

• Space: Interplanetary and interstellar travel, including faster-than-light travel; missions and permanent settlements on the Moon, Mars and the asteroid belt; space elevators
• Transportation & Energy: Self-driving and electric vehicles; improved mass transit systems and intercontinental travel; flying cars and hoverboards; high-efficiency solar and other sustainable energy sources
• Medicine & Health: Neurological devices for memory augmentation, storage and transfer, and perhaps to read people’s thoughts; life extension, including virtual immortality via uploading brains into computers; artificial cells and organs; “Star Trek”-style tricorder for home diagnostics and treatment; wearable technology, such as exoskeletons and augmented-reality glasses and contact lenses
• Materials & Robotics: Ubiquitous nanotechnology, 3-D printing and robotics; invisibility and cloaking devices; energy shields; anti-gravity devices
• Cyber & Big Data: Improved artificial intelligence; optical and quantum computing; faster, more secure Internet; better use of data analytics to improve use of resources

A few predictions inspired us to respond directly:

• “Pizza delivery via teleportation”—DARPA took a close look at this a few years ago and decided there is plenty of incentive for the private sector to handle this challenge.
• “Time travel technology will be close, but will be closely guarded by the military as a matter of national security”—We already did this tomorrow.
• “Systems for controlling the weather”—Meteorologists told us it would be a job killer and we didn’t want to rain on their parade.
• “Space colonies…and unlimited cellular data plans that won't be slowed by your carrier when you go over a limit”—We appreciate the idea that these are equally difficult, but they are not. We think likable cell-phone data plans are beyond even DARPA and a total non-starter.

So seriously, as an adjunct to this crowd-sourced view of the future, we asked three DARPA researchers from various fields to share their visions of 2045, and why getting there will require a group effort with players not only from academia and industry but from forward-looking government laboratories and agencies:

Pam Melroy, an aerospace engineer, former astronaut and current deputy director of DARPA’s Tactical Technologies Office (TTO), foresees technologies that would enable machines to collaborate with humans as partners on tasks far more complex than those we can tackle today:

Justin Sanchez, a neuroscientist and program manager in DARPA’s Biological Technologies Office (BTO), imagines a world where neurotechnologies could enable users to interact with their environment and other people by thought alone:

Stefanie Tompkins, a geologist and director of DARPA’s Defense Sciences Office, envisions building substances from the atomic or molecular level up to create “impossible” materials with previously unattainable capabilities.

Check back with us in 2045—or sooner, if that time machine stuff works out—for an assessment of how things really turned out in 30 years.

# # #

Associated images posted on www.darpa.mil and video posted at www.youtube.com/darpatv may be reused according to the terms of the DARPA User Agreement, available here:http://www.darpa.mil/policy/usage-policy.

Tweet @darpa

ORIGINAL: DARPA

OUTREACH@DARPA.MIL

10/21/2015

Stanford engineers create artificial skin that can send pressure sensation to brain cell

Stanford engineers have created a plastic skin-like material that can detect pressure and deliver a Morse code-like signal directly to a living brain cell. The work takes a big step toward adding a sense of touch to prosthetic limbs.

Stanford chemical engineering Professor Zhenan Bao and her team have created a skin-like material that can tell the difference between a soft touch and a firm handshake. The device on the golden “fingertip” is the skin-like sensor developed by Stanford engineers. (Bao Lab)

Stanford engineers have created a plastic "skin" that can detect how hard it is being pressed and generate an electric signal to deliver this sensory input directly to a living brain cell.

Zhenan Bao, a professor of chemical engineering at Stanford, has spent a decade trying to develop a material that mimics skin's ability to flex and heal, while also serving as the sensor net that sends touch, temperature and pain signals to the brain. Ultimately she wants to create a flexible electronic fabric embedded with sensors that could cover a prosthetic limb and replicate some of skin's sensory functions.

Bao's work, reported today in Science, takes another step toward her goal by replicating one aspect of touch, the sensory mechanism that enables us to distinguish the pressure difference between a limp handshake and a firm grip.

"This is the first time a flexible, skin-like material has been able to detect pressure and also transmit a signal to a component of the nervous system," said Bao, who led the 17-person research team responsible for the achievement.

Benjamin Tee, a recent doctoral graduate in electrical engineering; Alex Chortos, a doctoral candidate in materials science and engineering; and Andre Berndt, a postdoctoral scholar in bioengineering, were the lead authors on the Science paper.

DIGITIZING TOUCH

The heart of the technique is a two-ply plastic construct: the top layer creates a sensing mechanism and the bottom layer acts as the circuit to transport electrical signals and translate them into biochemical stimuli compatible with nerve cells. The top layer in the new work featured a sensor that can detect pressure over the same range as human skin, from a light finger tap to a firm handshake.

Five years ago, Bao's team members first described how to use plastics and rubbers as pressure sensors by measuring the natural springiness of their molecular structures. They then increased this natural pressure sensitivity by indenting a waffle pattern into the thin plastic, which further compresses the plastic's molecular springs.

To exploit this pressure-sensing capability electronically, the team scattered billions of carbon nanotubes through the waffled plastic. Putting pressure on the plastic squeezes the nanotubes closer together and enables them to conduct electricity.

This allowed the plastic sensor to mimic human skin, which transmits pressure information to the brain as short pulses of electricity, similar to Morse code. Increasing pressure on the waffled nanotubes squeezes them even closer together, allowing more electricity to flow through the sensor, and those varied impulses are sent as short pulses to the sensing mechanism. Remove pressure, and the flow of pulses relaxes, indicating light touch. Remove all pressure and the pulses cease entirely.

The team then hooked this pressure-sensing mechanism to the second ply of their artificial skin, a flexible electronic circuit that could carry pulses of electricity to nerve cells.

IMPORTING THE SIGNAL

Bao's team has been developing flexible electronics that can bend without breaking. For this project, team members worked with researchers from PARC, a Xerox company, which has a technology that uses an inkjet printer to deposit flexible circuits onto plastic. Covering a large surface is important to making artificial skin practical, and the PARC collaboration offered that prospect.

Finally the team had to prove that the electronic signal could be recognized by a biological neuron. It did this by adapting a technique developed by Karl Deisseroth, a fellow professor of bioengineering at Stanford who pioneered a field that combines genetics and optics, called optogenetics. Researchers bioengineer cells to make them sensitive to specific frequencies of light, then use light pulses to switch cells, or the processes being carried on inside them, on and off.

For this experiment the team members engineered a line of neurons to simulate a portion of the human nervous system. They translated the electronic pressure signals from the artificial skin into light pulses, which activated the neurons, proving that the artificial skin could generate a sensory output compatible with nerve cells.

Optogenetics was only used as an experimental proof of concept, Bao said, and other methods of stimulating nerves are likely to be used in real prosthetic devices. Bao's team has already worked with Bianxiao Cui, an associate professor of chemistry at Stanford, to show that direct stimulation of neurons with electrical pulses is possible.

Bao's team envisions developing different sensors to replicate, for instance, the ability to distinguish corduroy versus silk, or a cold glass of water from a hot cup of coffee. This will take time. There are six types of biological sensing mechanisms in the human hand, and the experiment described in Science reports success in just one of them.

But the current two-ply approach means the team can add sensations as it develops new mechanisms. And the inkjet printing fabrication process suggests how a network of sensors could be deposited over a flexible layer and folded over a prosthetic hand.

"We have a lot of work to take this from experimental to practical applications," Bao said. "But after spending many years in this work, I now see a clear path where we can take our artificial skin."

ORIGINAL: Stanford

By Tom Abate

First Optical Rectenna – Combined Rectifier and Antenna – Converts Light to DC Current

Using nanometer-scale components, researchers have demonstrated the first optical rectenna, a device that combines the functions of an antenna and a rectifier diode to convert light directly into DC current.

Using nanometer-scale components, researchers have demonstrated the first optical rectenna, a device that combines the functions of an antenna and a rectifier diode to convert light directly into DC current. 

Based on multiwall carbon nanotubes and tiny rectifiers fabricated onto them, the optical rectennas could provide a new technology for photodetectors that would operate without the need for cooling, energy harvesters that would convert waste heat to electricity – and ultimately for a new way to efficiently capture solar energy.

In the new devices, developed by engineers at the Georgia Institute of Technology, the carbon nanotubes act as antennas to capture light from the sun or other sources. As the waves of light hit the nanotube antennas, they create an oscillating charge that moves through rectifier devices attached to them. The rectifiers switch on and off at record high petahertz speeds (10¹⁵ Hz = 1Million GHz), creating a small direct current.

Optical rectenna converts laser light. A carbon nanotube optical rectenna converts green laser light to electricity in the laboratory of Baratunde Cola at the Georgia Institute of Technology. (Credit: Rob Felt, Georgia Tech)

Billions of rectennas in an array can produce significant current, though the efficiency of the devices demonstrated so far remains below one percent. The researchers hope to boost that output through optimization techniques, and believe that a rectenna with commercial potential may be available within a year.

“We could ultimately make solar cells that are twice as efficient at a cost that is ten times lower, and that is to me an opportunity to change the world in a very big way” said Baratunde Cola, an associate professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. “As a robust, high-temperature detector, these rectennas could be a completely disruptive technology if we can get to one percent efficiency. If we can get to higher efficiencies, we could apply it to energy conversion technologies and solar energy capture.”

The research, supported by the Defense Advanced Research Projects Agency (DARPA), the Space and Naval Warfare (SPAWAR) Systems Center and the Army Research Office (ARO), was reported September 28 in the journal Nature Nanotechnology.

Developed in the 1960s and 1970s, rectennas have operated at wavelengths as short as ten microns, but for more than 40 years researchers have been attempting to make devices at optical wavelengths. There were many challenges:

• making the antennas small enough to couple optical wavelengths, and 
• fabricating a matching rectifier diode small enough and 
• able to operate fast enough to capture the electromagnetic wave oscillations. 

But the potential of high efficiency and low cost kept scientists working on the technology.

“The physics and the scientific concepts have been out there,” said Cola. “Now was the perfect time to try some new things and make a device work, thanks to advances in fabrication technology.”

Using metallic multiwall carbon nanotubes and nanoscale fabrication techniques, Cola and collaborators Asha Sharma, Virendra Singh and Thomas Bougher constructed devices that utilize the wave nature of light rather than its particle nature. They also used a long series of tests – and more than a thousand devices – to verify measurements of both current and voltage to confirm the existence of rectenna functions that had been predicted theoretically. The devices operated at a range of temperatures from 5 to 77 degrees Celsius.

Optical rectenna schematic. This schematic shows the components of the optical rectenna developed at the Georgia Institute of Technology. (Credit: Thomas Bougher, Georgia Tech)

Fabricating the rectennas begins with 

• growing forests of vertically-aligned carbon nanotubes on a conductive substrate.
• Using atomic layer chemical vapor deposition, the nanotubes are coated with an aluminum oxide material to insulate them. 
• Finally, physical vapor deposition is used to deposit optically-transparent thin layers of calcium 
• then aluminum metals atop the nanotube forest. 

The difference of work functions between the nanotubes and the calcium provides a potential of about two electron volts, enough to drive electrons out of the carbon nanotube antennas when they are excited by light.

In operation, oscillating waves of light pass through the transparent calcium-aluminum electrode and interact with the nanotubes. The metal-insulator-metal junctions at the nanotube tips serve as rectifiers switching on and off at femtosecond (10^-15s = 1 millionth of nanosecond) intervals, allowing electrons generated by the antenna to flow one way into the top electrode. Ultra-low capacitance, on the order of a few attofarads (10^-6 Picofarads) , enables the 10-nanometer diameter diode to operate at these exceptional frequencies.

“A rectenna is basically an antenna coupled to a diode, but when you move into the optical spectrum, that usually means a nanoscale antenna coupled to a metal-insulator-metal diode,” Cola explained. “The closer you can get the antenna to the diode, the more efficient it is. So the ideal structure uses the antenna as one of the metals in the diode – which is the structure we made.”

The rectennas fabricated by Cola’s group are grown on rigid substrates, but the goal is to grow them on a foil or other material that would produce flexible solar cells or photodetectors.

Measuring output from optical rectenna. Georgia Tech associate professor Baratunde Cola measures the power produced by converting green laser illumination to electricity using the carbon nanotube optical rectenna. (Credit: Rob Felt, Georgia Tech)

Cola sees the rectennas built so far as simple proof of principle. He has ideas for how to improve the efficiency by changing the materials, opening the carbon nanotubes to allow multiple conduction channels, and reducing resistance in the structures.

“We think we can reduce the resistance by several orders of magnitude just by improving the fabrication of our device structures,” he said. “Based on what others have done and what the theory is showing us, I believe that these devices could get to greater than 40 percent efficiency.”

Professor Baratunde Cola (left) holds a carbon nanotube optical rectenna device. With him are Asha Sharma (center) and Virendra Singh from his group, who are collaborators on the development. (Credit: Candler Hobbs, Georgia Tech)

This work was supported by the Defense Advanced Research Projects Agency (DARPA), the Space and Naval Warfare (SPAWAR) Systems Center, Pacific under YFA grant N66001-09-1-2091, and by the Army Research Office (ARO), through the Young Investigator Program (YIP), under agreement W911NF-13-1-0491. The statements in this release are those of the authors and do not necessarily reflect the official views of DARPA, SPAWAR or ARO. Georgia Tech has filed international patent applications related to this work under PCT/US2013/065918 in the United States (U.S.S.N. 14/434,118), Europe (No. 13847632.0), Japan (No. 2015-538110) and China (No. 201380060639.2)

CITATION: Asha Sharma, Virendra Singh, Thomas L. Bougher and Baratunde A. Cola, “A carbon nanotube optical rectenna,” (Nature Nanotechnology, 2015). http://dx.doi.org/10.1038/nnano.2015.220

Research News

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Media Relations Contact: John Toon (jtoon@gatech.edu) (404-894-6986)

Writer: John Toon

ORIGINAL: Georgia Tech
By John Toon

September 28, 2015

Google Won The Internet. Now It Wants to Cure Diseases

Click to Open Overlay Gallery RAFE SWAN/GETTY IMAGES

WHEN GOOGLE CO-FOUNDER Larry Page dropped his now-famous blog post revealing that Google was reorganizing itself as Alphabet, one of the most striking things was what he chose to highlight as the kind of work these newly independent non-Google companies would be pursuing.

“The companies that are pretty far afield of our main Internet products [are] contained in Alphabet instead,” Page wrote in the blog post announcing Alphabet’s existence. “Good examples are our health efforts: Life Sciences (that works on the glucose-sensing contact lens), and Calico (focused on longevity).”

Google has long dabbled in medicine, but Page’s announcement signaled that he wants biomedical research to be more than just a side project for his newly christened company. Behind the scenes, efforts were already well under way to transform Google into a place that was serious about life sciences.

Under Alphabet, life sciences will become its own independent division, though it doesn’t have an official name just yet. (The company says to expect more news soon.) But a few hints suggest the life sciences group had been operating fairly independently already. Last month, CFO Ruth Porat singled out life sciences during a quarterly earnings call as one of the areas Google sees as “longer-term sources of revenue.” To get there, the company has been quietly recruiting top scientific talent, from immunologists to neurologists to nanoparticle engineers.

“Google Life Sciences is focused on shifting health care from a reactive, undifferentiated approach to a proactive, targeted approach,” reads one of the company’s recent job listings. Biomedical researchers at Google will work to transform the “detection, prevention, management and even our basic understanding of disease,” the company says. In other words, just like everything else it does, the company once known as Google intends to train its outsized ambition on fixing the most basic problems afflicting human health.

Building An Infrastructure

For the past two years, Google’s life science efforts have been headed up by Andrew Conrad, previously the chief scientific officer at LabCorp and the co-founder of the National Genetics Institute. He leads more than 150 scientists who come from fields as wide-ranging as astrophysics, theoretical math, and oncology. “Our central thesis was that there’s clearly something amiss in Western medicine,” Conrad told Steven Levy of Backchannel back in October.

Sam Gambhir, a professor of radiology, bioengineering, and materials science at Stanford University who has collaborated with Conrad since before Google Life Sciences was a formal division within Google X, says the division isn’t just playing around. Gambhir says projects on which he’s partnered with Google’s life sciences team include the use of nanotechnology to improve diagnostics as well as devices to continuously monitor biomarkers.

“They’re systematically building an infrastructure to tackle things in-house as well as collaborate with multiple universities,” Gambhir tells WIRED. “It’s a very serious effort, and it seems to have always been supported from the very top of the company.”

Tackling Chronic Disease

One of the longest-standing efforts has been a project to develop new ways of diagnosing and treating diabetes. Last year Google unveiled a smart contact lens diabetics can use to read blood sugar levels through the tears in their eyes. Pharmaceutical giant Novartis announced that it would license the smart lens tech from Google, and the two companies are exploring other uses for the tech. Just this month, Google announced it was partnering with Dexcom, a glucose-monitoring company, to focus on making a continuous glucose monitor that’s cheaper, more convenient than current solutions, and disposable, the company said.

Google is also diving deep into genomics. Gambhir says a committee of scientists from Google, Duke University, and Stanford University have been meeting multiple times a week for about a year now to work on the design of what Google has called its Baseline Study, a project that will ultimately collect anonymous genetic information from 10,000 people to create a “baseline” picture of what a healthy human being looks like on a molecular level. Gambhir, a collaborator on the project, says Baseline is intended to be a “longitudinal study on human health to understand the transition from health to disease.”

Other work on the molecular level include a cancer-detecting pill that pairs with a wristband, all part of what Google called its “nanoparticle platform.” Part of getting the wearable to work correctly included understanding how light passed through skin, which led Conrad and his team to make artificial human skin. Life Sciences is looking at other chronic diseases, too. In January, Conrad told Bloomberg that the team planned to partner with multiple sclerosis drugmaker Biogen to study environmental and biological contributors to the disease’s progression.

Ageless Problems

Last September, Google bought Lift Labs, maker of Liftware—a high-tech spoon designed to help people with neurodegenerative tremors eat. But Google wouldn’t be Google (er, Alphabet wouldn’t be Alphabet) if it was just concerned with addressing the symptoms of disease. Aging itself is another problem it hopes to disrupt. Calico, which is organizationally separate from the life sciences group, aims to maximize the human lifespan by preventing aging. The life sciences division, meanwhile, is focused on staving off diseases that could interfere with Calico’s goal. Neither of those efforts seems very closely tied to Google’s original business model of targeting ads to users based on Internet searches. Now that life sciences have become independent under Alphabet, it looks like they don’t have to be.

ORIGINAL: Wired

08.19.15