David Kirkpatrick

October 18, 2010

DARPA’s shooting for the stars


From the link:

NASA Ames Director Simon “Pete” Worden revealed Saturday that NASA Ames has “just started a project with DARPA called the Hundred Year Starship,” with $1 million funding from DARPA and $100K from NASA.

“You heard it here,” said Worden at “Long Conversation,” a Long Now Foundation event in San Francisco. “We also hope to inveigle some billionaires to form a Hundred Year Starship fund,” he added.

“The human space program is now really aimed at settling other worlds,” he explained. “Twenty years ago you had to whisper that in dark bars and get fired.” (Worden was in fact fired by President George W. Bush, he also revealed.)

But these ambitious projects will need whole new concepts for propulsion, Worden advised. “NASA needs to build a true starship, probably using electric propulsion, probably also using solar energy and nuclear energy.

Microwave thermal propulsion (Kevin Parker)


September 3, 2010

Cool nanotech image — a 2-water molecule thick ice crystal

Researchers used graphene to trap the room-temperature ice on a mica surface.

Atomic force micrograph of ~1 micrometer wide × 1.5 micrometers (millionths of a meter) tall area. The ice crystals (lightest blue) are 0.37 nanometers (billionths of a meter) high, which is the height of a 2-water molecule thick ice crystal. A one-atom thick sheet of graphene is used to conformally coat and trap water that has adsorbed onto a mica surface, permitting it to be imaged and characterized by atomic force microscopy. Detailed analysis of such images reveals that this (first layer) of water is ice, even at room temperature. At high humidity levels, a second layer of water will coat the first layer, also as ice. At very high humidity levels, additional layers of water will coat the surface as droplets. Credit: Heath group/Caltech

Hit the link for the full story on this image.

July 27, 2010

Artificial photosynthesis

I’ll keep my contribution here short and sweet — very interesting.

From the link:

The U.S. Department of Energy has awarded $122 million to establish a research center in California to develop ways of generating fuel made from sunlight. The project will be led by researchers at Caltech and the Lawrence Berkeley National Laboratory, and will include researchers at various other California institutions, including Stanford University, the University of California, Irvine, and the University of California, Berkeley.

Sun-soaked silicon: Researchers at the new Joint Center for Artificial Photosynthesis will work to optimize light-trapping silicon microwires, like these, to produce fuel from solar energy.

Credit: Nate Lewis, Caltech

May 13, 2010

Molecular nanobots

Via KurzweilAI.net — very cool! As always, I’ve included the entire KurzweilAI post. This one is a bit longer than usual.

How to make a molecular nanobot
KurzweilAI.net, May 13, 2010

Scientists have programmed an autonomous molecular nanorobot made out of DNA to start, move, turn, and stop while following a DNA track.

(Paul Michelotti)

The development could ultimately lead to molecular systems that could be used for medical therapeutic devices and molecular-scale reconfigurable robots—robots made of many simple units that can reposition or even rebuild themselves to accomplish different tasks.

Molecular robots, in theory, could be programmed to sense their environment (say, the presence of disease markers on a cell), make a decision (that the cell is cancerous and needs to be neutralized), and act on that decision (deliver a cargo of cancer-killing drugs). Or they could be programmed to assemble complex molecular products.

“In normal robotics, the robot itself contains the knowledge about the commands, but with individual molecules, you can’t store that amount of information, so the idea instead is to store information on the commands on the outside,” says Nils G. Walter, professor of chemistry and director of the Single Molecule Analysis in Real-Time (SMART) Center at the University of Michigan in Ann Arbor. And you do that by “imbuing the molecule‘s environment with informational cues,” says Milan N. Stojanovic, a faculty member in the Division of Experimental Therapeutics at Columbia University.

“We were able to create such a programmed or ‘prescribed’ environment using DNA origami,” explains Hao Yan, professor of chemistry and biochemistry at Arizona State University. DNA origami is a type of self-assembledstructure made from DNA that can be programmed to form nearly limitless shapes and patterns. Exploiting the sequence-recognition properties of DNA base pairing, DNA origami are created from a long single strand of DNA and a mixture of different short synthetic DNA strands that bind to and “staple” the long DNA into the desired shape. The origami used in the Nature study was a rectangle that was 2 nanometers (nm) thick and roughly 100 nm on each side.

The researchers constructed a trail of molecular “bread crumbs” on the DNA origami track by stringing additional single-stranded DNA molecules, or oligonucleotides, off the ends of the staples. These represent the cues that tell the molecular robots what to do—start, walk, turn left, turn right, or stop, for example—akin to the commands given to traditional robots.

To build the 4-nm-diameter molecular robot, the researchers started with a common protein called streptavidin, which has four symmetrically placed binding pockets for a chemical moiety called biotin. Each robot leg is a short biotin-labeled strand of DNA, “so this way we can bind up to four legs to the body of our robot,” Walter says. “It’s a four-legged spider,” quips Stojanovic. Three of the legs are made of enzymatic DNA, which is DNA that binds to and cuts a particular sequence of DNA. The spider also is outfitted with a “start strand”—the fourth leg—that tethers the spider to the start site (one particular oligonucleotide on the DNA origami track). “After the robotis released from its start site by a trigger strand, it follows the track by binding to and then cutting the DNA strands extending off of the staple strands on the molecular track,” Stojanovic explains.

“Once it cleaves,” adds Yan, “the product will dissociate, and the leg will start searching for the next substrate.” In this way, the spider is guided down the path laid out by the researchers. Finally, explains Yan, “the robot stops when it encounters a patch of DNA that it can bind to but that it cannot cut,” which acts as a sort of flypaper.

Using atomic force microscopy and single-molecule fluorescence microscopy, the researchers were able to watch spiders crawling over the origami, showing that they were able to guide their molecular robots to follow four different paths.

More info: Caltech news and Molecular robots guided by prescriptive landscapes

April 22, 2010

New negative-index metamaterial for invisibility cloaks and more

Here’s news on a new artificial optical material with applications for invisibility cloaking tech and more.

From the first link:

Caltech-led team designs novel negative-index metamaterial that responds to visible light

Uniquely versatile material could be used for more efficient light collection in solar cells

IMAGE: Arrays of coupled plasmonic coaxial waveguides offer a new approach by which to realize negative-index metamaterials that are remarkably insensitive to angle of incidence and polarization in the visible range….

Click here for more information.

PASADENA, Calif.—A group of scientists led by researchers from the California Institute of Technology (Caltech) has engineered a type of artificial optical material—a metamaterial—with a particular three-dimensional structure such that light exhibits a negative index of refraction upon entering the material. In other words, this material bends light in the “wrong” direction from what normally would be expected, irrespective of the angle of the approaching light.

This new type of negative-index metamaterial (NIM), described in an advance online publication in the journal Nature Materials, is simpler than previous NIMs—requiring only a single functional layer—and yet more versatile, in that it can handle light with any polarization over a broad range of incident angles. And it can do all of this in the blue part of the visible spectrum, making it “the first negative index metamaterial to operate at visible frequencies,” says graduate student Stanley Burgos, a researcher at the Light-Material Interactions in Energy Conversion Energy Frontier Research Center at Caltech and the paper’s first author.

“By engineering a metamaterial with such properties, we are opening the door to such unusual—but potentially useful—phenomena as superlensing (high-resolution imaging past the diffraction limit), invisibility cloaking, and the synthesis of materials index-matched to air, for potential enhancement of light collection in solar cells,” says Harry Atwater, Howard Hughes Professor and professor of applied physics and materials science, director of Caltech’s Resnick Institute, founding member of the Kavli Nanoscience Institute, and leader of the research team

What makes this NIM unique, says Burgos, is its engineering. “The source of the negative-index response is fundamentally different from that of previous NIM designs,” he explains. Those previous efforts used multiple layers of “resonant elements” to refract the light in this unusual way, while this version is composed of a single layer of silver permeated with “coupled plasmonic waveguide elements.”

Surface plasmons are light waves coupled to waves of electrons at the interface between a metal and a dielectric (a non-conducting material like air). Plasmonic waveguide elements route these coupled waves through the material. Not only is this material more feasible to fabricate than those previously used, Burgos says, it also allows for simple “tuning” of the negative-index response; by changing the materials used, or the geometry of the waveguide, the NIM can be tuned to respond to a different wavelength of light coming from nearly any angle with any polarization. “By carefully engineering the coupling between such waveguide elements, it was possible to develop a material with a nearly isotopic refractive index tuned to operate at visible frequencies.”

This sort of functional flexibility is critical if the material is to be used in a wide variety of ways, says Atwater. “For practical applications, it is very important for a material’s response to be insensitive to both incidence angle and polarization,” he says. “Take eyeglasses, for example. In order for them to properly focus light reflected off an object on the back of your eye, they must be able to accept and focus light coming from a broad range of angles, independent of polarization. Said another way, their response must be nearly isotropic. Our metamaterial has the same capabilities in terms of its response to incident light.”

This means the new metamaterial is particularly well suited to use in solar cells, Atwater adds. “The fact that our NIM design is tunable means we could potentially tune its index response to better match the solar spectrum, allowing for the development of broadband wide-angle metamaterials that could enhance light collection in solar cells,” he explains. “And the fact that the metamaterial has a wide-angle response is important because it means that it can ‘accept’ light from a broad range of angles. In the case of solar cells, this means more light collection and less reflected or ‘wasted’ light.”

“This work stands out because, through careful engineering, greater simplicity has been achieved,” says Ares Rosakis, chair of the Division of Engineering and Applied Science at Caltech and Theodore von Kármán Professor of Aeronautics and Mechanical Engineering.


In addition to Burgos and Atwater, the other authors on the Nature Materials paper, “A single-layer wide-angle negative index metamaterial at visible frequencies,” are Rene de Waele and Albert Polman from the Foundation for Fundamental Research on Matter Institute for Atomic and Molecular Physics in Amsterdam. Their work was supported by the Energy Frontier Research Centers program of the Office of Science of the Department of Energy, the National Science Foundation, the Nederlandse Organisatie voor Wetenschappelijk Onderzoek, and “NanoNed,” a nanotechnology program funded by the Dutch Ministry of Economic Affairs.

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