Nanodot: the original nanotechnology weblog

Nanowires of indium phosphide grown directly on an electrode greatly increase the flow of electrons through a polymer film to the electrode. Although still at the proof of concept stage, this nanotech innovation could ultimately lead to more efficient thin-film solar cells. Excerpts from a University of California, San Diego news release, by Daniel Kane “Nanowires May Boost Solar Cell Efficiency, UC San Diego Engineers Say” (credit PhysOrg.com)

University of California, San Diego electrical engineers have created experimental solar cells spiked with nanowires that could lead to highly efficient thin-film solar cells of the future.

Indium phosphide (InP) nanowires can serve as electron superhighways that carry electrons kicked loose by photons of light directly to the device’s electron-attracting electrode — and this scenario could boost thin-film solar cell efficiency, according to research recently published in Nano Letters (paper).

The new design increases the number of electrons that make it from the light-absorbing polymer to an electrode. By reducing electron-hole recombination, the UC San Diego engineers have demonstrated a way to increases the efficiency with which sunlight can be converted to electricity in thin-film photovoltaics.

Including nanowires in the experimental solar cell increased the “forward bias current” — which is a measure of electrical current — by six to seven orders of magnitude as compared to their polymer-only control device, the engineers found. Read the rest of this entry »

Arizona State University chemists have demonstrated a nanotech version of molecular self-regulation by designing a molecule that mimics the way in which plants defend themselves from an overload of sunshine by draining away the excess light energy as heat so that it can not generate destructive high energy intermediates. The nanotech molecule is composed of five components, one of which responds to light by reversibly changing shape. Excerpts from “Molecule With ‘Self-control’ Synthesized“:

…The ASU-designed molecule works in a similar fashion in that it converts absorbed light to electrochemical energy but reduces the efficiency of the conversion as light intensity increases. The ASU-designed molecule has several components including two light gathering antennas— a porphyrin electron donor, a fullerene acceptor and a control unit that reversibly photoisomerizes between a dihydroindolizine (DHI) and a betaine (BT).

When white light (sunlight) shines on a solution of the molecules, light absorbed by the porphyrin (or by the antennas) is converted to electrochemical potential energy. When the white light intensity is increased, the DHI on some molecules change to a different molecular structure, BT, that drains light excitation energy out of the porphyrin and converts it to heat, avoiding the generation of excess electrochemical potential. As the light becomes brighter, more molecules switch to the non-functional form, so that the conversion of light to chemical energy becomes less efficient. The molecule adapts to its environment, regulating its behavior in response to the light intensity. Read the rest of this entry »

In an application of nanotechnology to medicine, a nanotech material has been produced that self-assembles in the presence of bodily fluids into highly hydrated fibers that stop bleeding within 15 seconds, and which are harmlessly adsorbed by the body when no longer needed. The material also shows promise as a tissue engineering scaffold to facilitate healing in the central nervous system. Excerpts from “Nanohealing Material Heads to Market“, written by Kevin Bullis at Technology Review (via KurzweilAI.net):

A startup based in Cambridge, MA, says that it plans to soon begin clinical trials of a nanostructured material that stops bleeding almost instantly. A startup called Arch Therapeutics has licensed the technology from MIT and is developing manufacturing processes for making it in large amounts.

The new material can be poured over a site and will stop the bleeding almost at once.

The first application, pending Food and Drug Administration approval, will be for use during surgery to quickly stop bleeding and even prevent it in the first place. Floyd Loop, currently an advisor to Arch Therapeutics, and formerly a cardiovascular surgeon and the head of Cleveland Clinic, says that it could be useful in a wide variety of surgeries, including brain, heart, and prostate. For example, he says that when large tumors are removed, “there’s a lot of diffuse bleeding around the site, and you have to spend a lot of time with sponges and cautery stopping it.” Read the rest of this entry »

Nanotechnology—inspired by biology—can use catalytic motors to convert chemical to mechanical energy, using fuels that are chemically simpler than ATP—the energy currency of biology—and catalysts that are simpler than enzymes. In a Nanowerk Spotlight, Michael Berger describes nanotech catalytic motors for transporting micron-scale cargo. Excerpts from “Catalytic nanotransporters for nanotechnology applications outside biological systems“:

The catalytic conversion of chemical to mechanical energy is ubiquitous in biology, powering such important and diverse processes as cell division, skeletal muscle movement, protein synthesis, and transport of cargo within cells. Catalytic ‘engines’ will be key components of active micron- and sub-micron scale systems for controlled movement, particle assembly, and separations. …we show an example where catalytic nanomotors can, in principle, be tethered or coupled to other objects to act as the engines of nanoscale assemblies. Additionally, an object that moves by generating a continuous surface force in a fluid can, in principle, be used to pump the fluid by the same catalytic mechanism. Thus, by immobilizing these nanomotors, a group of scientists have developed micro/nanofluidic pumps that transduce energy catalytically.

“Until recently, catalytic micro- and nanomotors have been more or less unknown outside biology” Dr. Ayusman Sen explains to Nanowerk. “For nanotechnology researchers, catalyzed movement on the nanoscale is a fairly new phenomenon and there is much to be learned from nature’s motor systems. There is a good possibility that unexpected applications will arise from exploratory research.” Read the rest of this entry »

Sunday, May 18th at 7:00 PM Pacific / 10:00 PM Eastern, FastForward Radio will feature a distinguished panel discussing the Technology Roadmap for Productive Nanosystems.

The panel will discuss the background and history of the roadmap, and explore how it will serve to help realize these horizons. The panelists are:

• Christine Peterson, Acting President of Foresight Nanotech Institute
• Dr. David Forrest, President of the Institute for Molecular Manufacturing and a Senior Fellow at the Foresight Nanotech Institute
• Dr. Pearl Chin, Research Fellow with Foresight Nanotech

For more information, see The Speculist: “Panel to Discuss Productive Nanosystems“
—Jim

Can online gamers add to the nanotech toolkit for perfecting the de novo design of proteins that do not exist in nature? Prof. David Baker, who shared the 2004 Foresight Institute Feynman Prize in Nanotechnology in the Theoretical category, and whose milestone work in the protein engineering pathway to productive nanosystems was noted here two months ago (Major nanotechnology milestone: protein catalysts designed for non-natural chemical reactions), has invited online gamers to help develop better protein structures. Excerpts from “Biologists Enlist Online Gamers“, at Technology Review, written by Katherine Bourzac:

…The potential payoffs of making proteins that don’t exist in nature, such as those needed for HIV vaccines or as catalysts for more-efficient biofuel production, are huge. But making proteins to meet a specific need can be difficult.

Now a leading protein researcher has teamed up with computer scientists to create an online game for developing useful protein structures. David Baker, a leading protein scientist at the University of Washington, says that players will help his lab design new vaccines and make enzymes for repairing DNA in diseased tissues. Read the rest of this entry »

Using a spin-on coating that is applied to a silicon wafer, nanotech researchers have developed a method for mass fabrication of nanowire photonic and electronic devices. From Harvard University, via AAAS EurekAlert, “Scientists demonstrate method for integrating nanowire devices directly onto silicon“:

Fabrication technique could yield low-cost, scalable nanowire photonic and electronic circuits

Applied scientists at Harvard University in collaboration with researchers from the German universities of Jena, Gottingen, and Bremen, have developed a new technique for fabricating nanowire photonic and electronic integrated circuits that may one day be suitable for high-volume commercial production.

Spearheaded by graduate student Mariano Zimmler and Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, both of Harvard’s School of Engineering and Applied Sciences (SEAS), and Prof. Carsten Ronning of the University of Jena, the findings will be published in Nano Letters [abstract]. The researchers have filed for U.S. patents covering their invention. Read the rest of this entry »

A major advantage of nanotechnology in the race to develop better ways to deliver drugs to cancer cells is the wide variety of shapes and sizes that nanotech provides. Spherical nanoparticles are often cleared from circulation by the immune system in minutes—before they can have maximum impact on the cancer cells. Now researchers have joined about eight nanoparticles together to make nanostructures resembling segmented worms, and find these survive many hours. Excerpts from the UC San Diego News Center via ScienceDaily “UC San Diego Researchers Target Tumors with Tiny ‘Nanoworms’“:

Scientists at UC San Diego, UC Santa Barbara and MIT have developed nanometer-sized “nanoworms” that can cruise through the bloodstream without significant interference from the body’s immune defense system and—like tiny anti-cancer missiles—home in on tumors.

Their discovery, detailed in this week’s issue of the journal Advanced Materials [abstract], is reminiscent of the 1966 science fiction movie, the Fantastic Voyage, in which a submarine is shrunken to microscopic dimensions, then injected into the bloodstream to remove a blood clot from a diplomat’s brain.

Using nanoworms, doctors should eventually be able to target and reveal the location of developing tumors that are too small to detect by conventional methods. Carrying payloads targeted to specific features on tumors, these microscopic vehicles could also one day provide the means to more effectively deliver toxic anti-cancer drugs to these tumors in high concentrations without negatively impacting other parts of the body. Read the rest of this entry »

There is hope that nanotechnology in the form of silver nanoparticles will provide protection against drug-resistant bacteria in hospitals, but there is also concern that unregulated use of silver nanoparticles in commercial products will damage the environment. A mention on KurzweilAI.net led to this article by Monica Heger on SciAm.com News, provided originally by Scienceline. From “A Silver Coating in the Fight Against Microbes“:

A new technique in paint making could soon make almost any surface germ-free. Researchers have made paint that is embedded with silver nanoparticles, known for their ability to kill bacteria and other microbes, in the hopes that hospitals will coat their walls and countertops to fight infection.

According to the U.S. Centers for Disease Control and Prevention, more than 1 million people per year contract bacterial infections in hospitals. Silver itself is an excellent bacteria fighter, and in nanoparticle form it is even more potent at killing microorganisms. So far it has not shown any adverse effects in humans.

However, some scientists are concerned that silver nanoparticles may not be as harmless as they appear. Little research has been done on their health and environmental effects, and silver kills good microorganisms along with the bad. Also, there are currently no restrictions on using silver nanoparticles, which are already popping up in a range of consumer products that tout their antibacterial properties. Read the rest of this entry »

A while back Senior Associate Stuart Scott let us know that he had been selected to participate in a National Citizen’s Technology Forum process on nanotechnology, sponsored by Arizona State and University of North Carolina, among other schools. Presumably this is funded by the social science budget of the U.S. National Nanotechnology Initiative, via NSF. Regarding topics covered, Stuart commented: “Their interest seems to be transhumanism, nanotechnology as applied to augmentation, and ‘public policy’ implications such as how should ‘we’ allocate things when not all can afford them.”

He sent the URL for notes on interests and concerns from the human enhancement policy discussions: http://www4.ncsu.edu/~pwhmds/notes.html
and the final reports: http://www4.ncsu.edu/~pwhmds/final_reports.html

Stuart commented:

I thought that Arizona’s was one of the better and that Wisconson and New Hampshire were about as expected. What, if any, impact they will have is open to speculation. From the response the project operators made, this technique might be used more in the future. It was a part of the experiment as well as the topic.

If you have thoughts on the process or reports, we’d like to hear them. Just comment on this blog post. —Christine

Some nanostructures can be improved after fabrication by a new nanotech procedure that transiently and selectively liquifies the structures to remove defects. From “Self-perfection in nanomanufacturing“, a Nanowerk Spotlight written by Michael Berger:

…Rather than perfecting a nanostructure by improving its original fabrication method, researchers at Princeton University have demonstrated a new method, known as self-perfection by liquefaction (SPEL), which removes nanostructure fabrication defects and improves nanostructures after fabrication.

“When feature sizes in a device are small enough, the fabrication defects in many nanofabrication methods can become a dominant factor that determines the actual shape of the nanostructure” Dr. Stephen Y. Chou explains to Nanowerk. “Although extrinsic defects can be removed by improving the process, intrinsic defects caused by the fundamental statistical nature of a fabrication process — for example, noise in photon, electron or ion generation, scattering, and variations in chemical reaction — cannot be removed within the process regardless of improvements to it. The minimum line width and line height are often determined by the fundamental working principle of a fabrication, and are fixed once a fabrication method is selected.”

“Our process removes defects after fabrication rather than in the fabrication. As structures become very small, conventional fabrications will be limited by intrinsic noise, and improving the fabrication technology becomes fruitless.” Read the rest of this entry »

We’ve received an invitation to participate in the Center for Nanotechnology in Society’s project to build and critique nanotechnology scenarios.

Current topics to edit in the wiki, or you can add your own:
* Barless Prisons
* Bionic Eyes
* Living with a Brain Chip
* Disease Detector
* Automated Sewer Surveillance
* Engineered Tissues

Read the rest of this entry »

Studies of how molecules are released from nanoparticles when they encounter cancer cells and of how the nanoparticles break down prematurely while circulating in the blood point toward ways to improve the nanotech delivery of therapeutic drugs into cancer cells. From “Imaging yields insights into ‘nanomedicine’ for cancer treatment“, a Purdue University news release written by Emil Venere, via Nanowerk News:

Researchers at Purdue University have discovered a possible new pathway for anti-tumor drugs to kill cancer cells and proposed how to improve the design of tiny drug-delivery particles for use in “nanomedicine.”

The synthetic “polymer micelles” are drug-delivery spheres 60-100 nanometers in diameter, or roughly 100 times smaller than a red blood cell. The spheres harbor drugs in their inner core and contain an outer shell made of a material called polyethylene glycol.

Purdue researchers showed for the first time how this shell of polyethylene glycol latches onto the membranes of cancer cells, allowing fluorescent probes mimicking cancer drugs to enter the cancer cells, said Ji-Xin Cheng, an assistant professor in the Weldon School of Biomedical Engineering and Department of Chemistry. Read the rest of this entry »

Preliminary theoretical calculations show that it might be possible to develop a nanotech application in which clusters of a few boron atoms connect very small graphene semiconductors to make nanoelectronic devices. From nanotechweb.org, written by Belle Dumé (requires free registration) “Nanowiring using boron clusters“:

A model system that could serve as a “blueprint” for graphene-based nanodevices of the future has been put forward by scientists in Italy, Turkey and Germany. The model involves using alternating chains of boron clusters to connect various parts of a semiconducting graphene substrate. The concept is very similar to that routinely employed in silicon-based integrated circuits, but the resulting graphene-based devices would be several orders of magnitude smaller.

Graphene is set to become one of the key materials in future nanotechnology applications. However, graphene-based devices studied so far are on the micron rather than nanoscale because they mainly consist of broad sheets of graphene connected by wiring of about the same size.

Now, Jens Kunstmann of the Max-Planck Institute for Festkörperforschung in Stuttgart and colleagues have proposed a way to take the wiring down to the nanoscale by implanting chains of B7 clusters into the graphene matrix. These clusters might then be used to connect various areas of a semiconducting graphene substrate. Read the rest of this entry »

At the macro scale engineered motors are far more powerful than biological motors, but this has not been true with nanotech motors. Now, by adding carbon nanotubes to catalytic nanowires, nanotechnology has produced simple nanomotors that can surpass biological motors (somewhat). From the American Chemical Society, via AAAS EurekAlert “Go Speed Racer! Revving up the world’s fastest nanomotors“:

In a “major step” toward a practical energy source for powering tomorrow’s nanomachines, researchers in Arizona report development of a new generation of sub-microscopic nanomotors that are up to 10 times more powerful than existing motors.

In the new study, Joseph Wang and colleagues point out that existing nanomotors, including so-called “catalytic nanomotors,” are made with gold and platinum nanowires and use hydrogen peroxide fuel for self-propulsion. But these motors are too slow and inefficient for practical use, with top speeds of about 10 micrometers per second, the researchers say…

Wang and colleagues supercharged their nanomotors by inserting carbon nanotubes into the platinum, thus boosting average speed to 60 micrometers per second. Spiking the hydrogen peroxide fuel with hydrazine (a type of rocket fuel) kicked up the speed still further, to 94-200 micrometers per second. This innovation “offers great promise for self-powered nanoscale transport and delivery systems,” the scientists state.

The research is published in ACS Nano (abstract)
—Jim

Forests of spiraling nanotrees made from lead sulfide nanowires may lead to new nanotech approaches for producing one-dimensional nanostructures based on designed dislocations rather than metal catalysts to control growth. From the University of Wisconsin-Madison, via AAAS EurekAlert, “Spiraling nanotrees offer new twist on growth of nanowires“:

Since scientists first learned to make nanowires, the nano-sized wires just a few millionths of a centimeter thick have taken many forms, including nanobelts, nanocoils and nanoflowers.

But when University of Wisconsin-Madison chemistry professor Song Jin and graduate student Matthew Bierman accidentally made some pine tree shapes one day — complete with tall trunks and branches that tapered in length as they spiraled upward — they knew they’d stumbled upon something peculiar.

… Writing in the May 1 edition of Science Express [abstract], Jin and his team reveal just how curious the nanotrees truly are. In fact, they’re evidence of an entirely different way of growing nanowires, one that promises to give scientists a powerful means to create new and better nanomaterials for all sorts of applications, including high-performance integrated circuits, biosensors, solar cells, LEDs and lasers. Read the rest of this entry »

RNA interference (RNAi) is a way to decrease expression of a specific gene without otherwise affecting the cell, and it therefore could be a very promising treatment for a wide variety of diseases—if it could be reliably delivered into the diseased cell cytoplasm. One possible nanotech solution to this problem takes the form of a 10-fold more effective delivery of RNAi protected in nanocapsules formed by novel lipid-like molecules. From “Nano RNA delivery: Novel delivery agents could mean a more targeted way to turn off disease genes” at Technology Review, written by Kevin Bullis (credit to KurzweilAI.net):

An experimental and potentially powerful way to fight disease, called RNA interference (RNAi), could now be closer to reality, as researchers at MIT and Alnylam, a biotech company based in Cambridge, MA, have addressed a key obstacle to effectively delivering the treatment to targeted cells. The researchers report a method for quickly synthesizing more than a thousand different lipid-like molecules and screening them for their ability to deliver short RNA molecules to cells. They’ve shown that some of these delivery agents are 10 times as effective at delivering RNA than previous methods were. Read the rest of this entry »

Nanotechnology has provided a fourth fundamental two-terminal passive element for electronic circuits—one first theoretically predicted 37 years ago, but only made physically possible by nanotechnology. Now joining resistors, capacitors and inductors is a nanotech device named the ‘memristor’, developed by a team led by R. Stanley Williams, who shared the 2000 Foresight Nanotech Institute Feynman Prize for Experimental work. From “H.P. Unveils New Memory Technology“, written by John Markoff for The New York TImes:

A team of Hewlett-Packard scientists reported Wednesday in the science journal Nature [abstract] that they have designed a simple circuit element they believe will enable tiny powerful computers that could imitate biological functions.

The device, called a memristor, could make it possible to build extremely dense computer memory chips that use far less power than today’s DRAM memory chips, which are rapidly reaching the limit in how much smaller they can be made.

The memristor, an electrical resistor with memory properties, may also make it possible to fashion advanced logic circuits, like a class of reprogrammable chips known as field programmable gate arrays, that are today widely used for rapid prototyping of new circuits and for custom-made chips that need to be manufactured quickly. Read the rest of this entry »

A special issue of the International Journal of Nanomanufacturing presenting topics on manufacturing in 3D at the nanoscale (derived from the 4th International Symposium on Nanomanufacturing held at MIT in November 2006) contains a report of a nanomanipulator for the complex assembly of nanoparticles. Although the press release from Inderscience Publishers, via AAAS EurekAlert (”Are nanobots on their way? US researchers have built a proto-prototype nano assembler“) explicitly references Eric Drexler’s 1986 description of an assembler, it is not clear (to me) from what is presented how close this mechanism might come to atomically precise manufacturing.

…Jason Gorman of the Intelligent Systems Division at the US government’s National Institute of Standards and Technology (NIST) … and his colleagues at NIST have taken a novel approach to building a nanoassembler and reveal details in a forthcoming issue of the International Journal of Nanomanufacturing [abstract]. “Our demonstration is still a work in progress,” says Gorman, “you might describe it as a ‘proto-prototype’ for a nanoassembler.”

…The NIST system consists of four Microelectromechanical Systems (MEMS) devices positioned around a centrally located port on a chip into which the starting materials can be placed. Each nanomanipulator is composed of positioning mechanism with an attached nanoprobe. By simultaneously controlling the position of each of these nanoprobes, the team can use them to cooperatively assemble a complex structure on a very small scale. “If successful, this project will result in an on-chip nanomanufacturing system that would be the first of its kind,” says Gorman. Read the rest of this entry »

A new building block for structural DNA nanotechnology uses a 3-carbon glycerol molecule instead of the 5-carbon sugar deoxyribose found in DNA. To begin exploring this new DNA nanotech, the researchers made a simple four-helix junction of the type pioneered in Ned Seeman’s laboratory, and found that nanostructures built from GNA not only tolerate higher temperatures than do comparable structures made with DNA, but both left-handed and right-handed four-helix junctions are obtained—something not easily done with DNA. An excerpt from “Scientists make chemical cousin of DNA for use as new nanotechnology building block” from Arizona State University, via AAAS EurekAlert:

In the Biodesign Institute at Arizona State University, researchers are using DNA to make intricate nano-sized objects. Working at this scale holds great potential for advancing medical and electronic applications. DNA, often thought of as the molecule of life, is an ideal building block for nanotechnology because they self-assemble, snapping together into shapes based on natural chemical rules of attraction. This is a major advantage for Biodesign researchers like Hao Yan, who rely on the unique chemical and physical properties of DNA to make their complex nanostructures.

While scientists are fully exploring the promise of DNA nanotechnology, Biodesign Institute colleague John Chaput is working to give researchers brand new materials to aid their designs. In an article recently published in the Journal of the American Chemical Society [abstract], Chaput and his research team have made the first self-assembled nanostructures composed entirely of glycerol nucleic acid (GNA)—a synthetic analog of DNA. Read the rest of this entry »