Personalized Life Extension 2012
Mar 31-Apr 1, 2012
South San Francisco
http://lifeextensionconference.com/

Hi folks — Join fellow Foresight members, self-trackers, self-experimenters, and health geeks to explore the latest ways to optimize your body and brain & slow aging.

Foresight is a partner on the conference, so we can use discount code NANODOT for $100 off.

If you plan to register but haven’t quite gotten around to it, now is the time. Tomorrow, March 14, is the cutoff for early rate registration, and also the deadline for the hotel room discount (see Logistics page).

Not sure? Check out the program, look through the blog posts, and see the list of participants on the registration page. Lots of Foresight names on that list.

Based on feedback from last time, I can say for certain that you’ll be healthier if you join us for this meeting. Hope to meet you there! –Christine Peterson, Conference Chairman & Foresight co-founder

Image courtesy of the Wyss Institute

“The nanosized robot was created in the form of an open barrel whose two halves are connected by a hinge. The DNA barrel, which acts as a container, is held shut by special DNA latches that can recognize and seek out combinations of cell-surface proteins, including disease markers. This image was created by Campbell Strong, Shawn Douglas, and Gaël McGill using Molecular Maya and cadnano.“

DNA nanotechnology is not only a very promising path toward productive nanosystems and atomically precise manufacturing, but also a path to increasingly sophisticated DNA molecular machines for near-term drug delivery applications in nanomedicine. A recent advance comprises an autonomous DNA nanorobot incorporating a DNA origami chasis and DNA aptamer locks functioning as logical AND gates that are unlocked after the aptamers bind a protein target on the target cell, allowing the nanorobot to discharge its therapeutic cargo. A hat tip to KurzweilAI.net for reprinting this Harvard Gazette news release written by Twig Mowatt “Sending DNA robot to do the job: Technology has potential to seek out cancer cells, cause them to self-destruct“:

Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University have developed a robotic device made from DNA that could potentially seek out specific cell targets within a complex mixture of cell types and deliver important molecular instructions, such as telling cancer cells to self-destruct. Inspired by the mechanics of the body’s own immune system, the technology might one day be used to program immune responses to treat various diseases. The research findings appear today in Science ["A Logic-Gated Nanorobot for Targeted Transport of Molecular Payloads" abstract; full text available for fair use on Church lab web site].

Using the DNA origami method, in which complex 3-D shapes and objects are constructed by folding strands of DNA, Shawn Douglas, a Wyss Technology Development Fellow, and Ido Bachelet, a former Wyss postdoctoral fellow who is now an assistant professor in the Faculty of Life Sciences and the Nano-Center at Bar-Ilan University in Israel, created a nanosized robot in the form of an open barrel whose two halves are connected by a hinge. The DNA barrel, which acts as a container, is held shut by special DNA latches that can recognize and seek out combinations of cell-surface proteins, including disease markers. When the latches find their targets, they reconfigure, causing the two halves of the barrel to swing open and expose its contents, or payload. The container can hold various types of payloads, including specific molecules with encoded instructions that can interact with specific cell surface signaling receptors.

Douglas and Bachelet used this system to deliver instructions, which were encoded in antibody fragments, to two different types of cancer cells — leukemia and lymphoma. In each case, the message to the cell was to activate its “suicide switch” — a standard feature that allows aging or abnormal cells to be eliminated. And because leukemia and lymphoma cells speak different languages, the messages were written in different antibody combinations. …

“We can finally integrate sensing and logical computing functions via complex, yet predictable, nanostructures — some of the first hybrids of structural DNA, antibodies, aptamers, and metal atomic clusters — aimed at useful, very specific targeting of human cancers and T-cells,” said George Church, a Wyss core faculty member and professor of genetics at Harvard Medical School, who is principal investigator on the project. …

A key feature of this work is that the DNA aptamer changes structure upon binding its target so it releases its hold on the complementary part of the DNA latch. Since two DNA latches hold the nanorobot in a closed configuration, the latches can be programmed to both respond to the same cell surface target, or to each respond to a different target so that both targets would need to be on the cell to activate the nanorobot to open and allow the payload molecules to bind their targets. This logical AND function allows for much greater specificity in recognizing target cells. As the authors conclude, “These findings demonstrate that the robots can induce a variety of tunable changes in cell behavior.” Conceivably a similar mechanism could be used in an atomically precise manufacturing operation in which DNA nanorobots could add a payload molecule to a workpiece depending on whether both of two specific molecular signals on the workpiece were present.
—James Lewis

John Walker, a longtime friend to nanotech and Foresight, sends this news about a TEDxBerkeley video:

Carl Bass, successor to the successor to the successor to me as CEO of Autodesk got up in front of an audience and spoke on “The Five New Rules of Innovation” among which was nanoscale and bio-inspired structures.

Unlike when I did it all those many years ago, nobody giggled.

And they say there isn’t progress!

Video (17 minutes–the nano bit is short, but it’s there):

John Walker’s thoughts on nanotechnoloogy were published about 22 years ago in a Foresight Briefing “What Next? Nanotechnology for Manufacturing“. The definitive copy of this essay, with the complete set of illustrations, is available on John Walker’s Web site.

RNA structural motif identification is essential in understanding the RNA architecture and functionalities. The illustration shows a novel RNA structural motif, named 'rope sling motif', identified by a newly developed computational framework … - Credit: C. Zhong and S. Zhang, Nucleic Acids Res., 2012, 40:1307–1317

As we pointed out recently, a unique advantage of RNA nanotechnology compared to DNA nanotechnology is that the more complex rules of base pairing involved in RNA folding allow the formation of a variety of compact, complex three-dimensional shapes. Although one principal function of RNA molecules in cells is as messenger RNA, carrying a copy of the information in a DNA gene to the ribosomes where that message is translated to make a protein, a large number of other RNA molecules, including those comprising the ribosomes themselves, have complex three-dimensional shapes and embody various functional properties dependent on those shapes, as do proteins.

Taking advantage of the rapid increase in available high resolution, three-dimensional structures for various non-coding RNA molecules, a new computational method has uncovered many new RNA structural motifs, revealing the tool kit of RNA nanotechnology to be even more diverse than thought. A hat tip to Science Daily for reprinting this news release from the University of Central Florida “Computer Sleuthing Helps Unravel RNA’s Role in Cellular Function“:

… University of Central Florida Engineering Assistant Professor Shaojie Zhang used a complex computer program to analyze RNA motifs – the subunits that make up RNA (ribonucleic acid). …

The units that make up RNA fold like a long accordion and vary in structure. Many have been identified in the past, but finding a quick automatic way to determine patterns in the varying types of units has been elusive until now.
“We have discovered many new RNA structural motifs using our new computational method,” Zhang said. “This breakthrough can largely increase our current knowledge of RNA structural motifs. And newly discovered motifs may also help us develop possible treatment of certain diseases.”

Zhang’s work is this month’s cover story in Nucleic Acids Research [abstract, Open Access Full Text], an academic journal.

Using computers, Zhang and his team have been able to view these RNA accordion-like structures and how they fold in a 3-D scale. The program can quickly go through many RNA samples and discover units that are distinct and form patterns. That information gives researchers clues about their function. …

The newly identified structural motifs contain variations in base-pairing rules. As the authors conclude:

These new motifs may lead to the discovery of unknown structure–function relationships and define new building blocks for the RNA architecture, significantly improving our understanding of the RNA structural motifs. …

The next test will be to see if these new insights into RNA structure will enable the design of new RNA machines with novel functions, and eventually artificial RNA molecular machines.
—James Lewis

Join us for an intellectually stimulating evening with best-selling author and tech analyst Sonia Arrison! Dinner and drinks will be served h’orderve/tapas-style at 7pm; Sonia will present at 8pm, with personalized, small-group Q&A on the future of technology to follow.

Wednesday March 21, 2012 at Ristorante Don Giovanni, 235 Castro Street, Mountain View, CA 94041

This is a limited-audience event; to RSVP, please Paypal $40 to foresight@foresight.org at http://www.paypal.com/

SONIA ARRISON is a bestselling author and technology analyst who has studied the impact of new technologies on society for more than a decade. Her book, 100 PLUS: How the Coming Age of Longevity will Change Everything, From Careers and Relationships to Family and Faith, is a national bestseller and has been featured in top media outlets such as the Wall Street Journal, The Economist, MSNBC, Bloomberg News, Fox News, and the Today Show.

As a founder, academic advisor, and trustee of Singularity University, she is focused on exponentially growing technologies and their impact on society. She is also a Senior Fellow at the California-based Pacific Research Institute for Public Policy (PRI) and a columnist for TechNewsWorld. She is author of three books and numerous PRI studies and was also the host of a radio show called “digital dialogue” on the Voice America network.

What are reviewers saying about 100+?

NEW SCIENTIST
“Brilliant …. The chapters devoted to advances in regenerative medicine and the search for interventions that slow ageing are exhilarating. Growing new limbs, copying internal organs like a Xerox machine, exponential increases in computing power, better eyes and ears—I could read stories like this endlessly. We need such vision to help carry the science forward, and some of the most exciting advances in the scientific study of ageing are forthcoming. Arrison paints a realistic picture of the science driving the next longevity revolution, and makes the case that, if we play our cards right, humanity will reap huge dividends for the effort. In that way, this book is the most comprehensive treatment of the socioeconomic consequences of life extension that I’ve seen …. [T]he costs and benefits of life extension and, more importantly, health extension, are subjects in desperate need of open dialogue, and Arrison begins this process with elegance and style.”

WALL STREET JOURNAL
“Ms. Arrison entertainingly chronicles efforts to conquer aging and death from antiquity to today. Food, sex, exercise and alchemy have all been employed to keep the grim reaper at bay. But technology offers the most plausible route, she says, noting that biology and computing are drawing ever closer together with the sequencing of the human genome …. [Her] sunny outlook is infectious.”

SINGULARITY HUB
“Easy to read, and easy to understand, 100+ walks you through the incredible achievements in regenerative medicine we’ve already seen, projects them forward, and discusses the changes in environment, economy, family, and religion that will follow…. Arrison states her case strongly enough to convince almost anyone, and in a style that will be as accessible to your techno-phobic Uncle Walter as it is to your computer loving self.”

Remember, space is limited! To RSVP, Paypal $40 to foresight@foresight.org at http://www.paypal.com/

Join us for an intellectually stimulating evening with best-selling author and tech analyst Sonia Arrison! Dinner and drinks will be served h’orderve/tapas-style at 7pm; Sonia will present at 8pm, with personalized, small-group Q&A on the future of technology to follow.

Wednesday March 21, 2012 at Ristorante Don Giovanni, 235 Castro Street, Mountain View, CA 94041

This is a limited-audience event; to RSVP, please Paypal $40 to foresight@foresight.org at http://www.paypal.com/

SONIA ARRISON is a bestselling author and technology analyst who has studied the impact of new technologies on society for more than a decade. Her book, 100 PLUS: How the Coming Age of Longevity will Change Everything, From Careers and Relationships to Family and Faith, is a national bestseller and has been featured in top media outlets such as the Wall Street Journal, The Economist, MSNBC, Bloomberg News, Fox News, and the Today Show.

As a founder, academic advisor, and trustee of Singularity University, she is focused on exponentially growing technologies and their impact on society. She is also a Senior Fellow at the California-based Pacific Research Institute for Public Policy (PRI) and a columnist for TechNewsWorld. She is author of three books and numerous PRI studies and was also the host of a radio show called “digital dialogue” on the Voice America network.

What are reviewers saying about 100+?

NEW SCIENTIST
“Brilliant …. The chapters devoted to advances in regenerative medicine and the search for interventions that slow ageing are exhilarating. Growing new limbs, copying internal organs like a Xerox machine, exponential increases in computing power, better eyes and ears—I could read stories like this endlessly. We need such vision to help carry the science forward, and some of the most exciting advances in the scientific study of ageing are forthcoming. Arrison paints a realistic picture of the science driving the next longevity revolution, and makes the case that, if we play our cards right, humanity will reap huge dividends for the effort. In that way, this book is the most comprehensive treatment of the socioeconomic consequences of life extension that I’ve seen …. [T]he costs and benefits of life extension and, more importantly, health extension, are subjects in desperate need of open dialogue, and Arrison begins this process with elegance and style.”

WALL STREET JOURNAL
“Ms. Arrison entertainingly chronicles efforts to conquer aging and death from antiquity to today. Food, sex, exercise and alchemy have all been employed to keep the grim reaper at bay. But technology offers the most plausible route, she says, noting that biology and computing are drawing ever closer together with the sequencing of the human genome …. [Her] sunny outlook is infectious.”

SINGULARITY HUB
“Easy to read, and easy to understand, 100+ walks you through the incredible achievements in regenerative medicine we’ve already seen, projects them forward, and discusses the changes in environment, economy, family, and religion that will follow…. Arrison states her case strongly enough to convince almost anyone, and in a style that will be as accessible to your techno-phobic Uncle Walter as it is to your computer loving self.”

Remember, space is limited! To RSVP, Paypal $40 to foresight@foresight.org at http://www.paypal.com/

At various points along the path toward productive nanosystems for molecular manufacturing it would be useful to be able to calculate the properties and reactions of assemblies of atoms of various sizes. Within the domain of non-relativistic quantum mechanics, such information is supplied by the Schrödinger equation, but this can only be solved analytically for the hydrogen atom and ions with only one electron. For larger atoms and molecules, numerical solutions require compromises between computational feasibility and accuracy. Recent work from researchers at Argonne National Laboratory suggests that machine learning can be an efficient alternative to numerical computations. A hat tip to KurzweilAI.net for pointing to this New Scientist article by Lisa Grossman “Molecules from scratch without the fiendish physics“:

A SUITE of artificial intelligence algorithms may become the ultimate chemistry set. Software can now quickly predict a property of molecules from their theoretical structure. Similar advances should allow chemists to design new molecules on computers instead of by lengthy trial-and-error.

Our physical understanding of the macroscopic world is so good that everything from bridges to aircraft can be designed and tested on a computer. There’s no need to make every possible design to figure out which ones work. Microscopic molecules are a different story. “Basically, we are still doing chemistry like Thomas Edison,” says Anatole von Lilienfeld of Argonne National Laboratory in Lemont, Illinois.

The chief enemy of computer-aided chemical design is the Schrödinger equation. In theory, this mathematical beast can be solved to give the probability that electrons in an atom or molecule will be in certain positions, giving rise to chemical and physical properties.

But because the equation increases in complexity as more electrons and protons are introduced, exact solutions only exist for the simplest systems: the hydrogen atom, composed of one electron and one proton, and the hydrogen molecule, which has two electrons and two protons. …

The researchers developed a machine learning model to calculate the atomisation energy—the energy of all the bonds holding a molecule together and applied it to a database of 7165 small organic molecules of known structure and atomization energy and containing up to seven atoms of carbon, nitrogen, oxygen, or sulfur, plus the number of hydrogen atoms necessary to saturate the bonds. These molecules had atomization energies ranging from 800 to 2000 kcal/mol. The model was trained on a subset of 1000 compounds and then used to calculate the energies of the remaining molecules in the database. The results showed a mean error of only 9.9 kcal/mol, comparable to the accuracy of methods based upon the Schrödinger equation, but the computations were done in milliseconds rather than hours. The authors suggest that extensions of their approach might permit rational molecule design or molecular dynamics calculations of systems of atoms undergoing chemical reactions.

The research was published in Physical Review Letters [abstract]. A free full text preprint is available.
—James Lewis

A new optimistic look at the future Abundance: The future is better than you think co-authored by Foresight Advisor Peter Diamandis and science writer Steven Kotler has hit #1 on both Amazon and BarnesAndNoble this morning (Monday, Feb. 20, 2012). From the book’s web site:

Since the dawn of humanity, a privileged few have lived in stark contrast to the hardscrabble majority. Conventional wisdom says this gap cannot be closed. But it is closing—fast. In Abundance, space entrepreneur turned innovation pioneer Peter H. Diamandis and award-winning science writer Steven Kotler document how progress in artificial intelligence, robotics, infinite computing, ubiquitous broadband networks, digital manufacturing, nanomaterials, synthetic biology, and many other exponentially growing technologies will enable us to make greater gains in the next two decades than we have in the previous two hundred years. We will soon have the ability to meet and exceed the basic needs of every man, woman, and child on the planet. Abundance for all is within our grasp. …

Providing abundance is humanity’s grandest challenge—this is a book about how we rise to meet it.

A preview of Chapter 1 and other information is available on the Abundance web site. Kudos to Diamandis and Kotler for showing why the future is brighter than it appears, and laying out a roadmap to get there.
—James Lewis

Credit: Lab of Jene Golovchenko, Harvard University

One of the greatest promises of near-term nanotechnoloogy is cheaper DNA sequencing to speed the development of personalized medicine. There are not only genetic differences between different patients, but also genetic differences between, for example, different cancers of the same organ diagnosed in different patients, or even from different locations in the same patient, that can greatly affect the success of a therapy. Nanopore sensors are among the promising new third-generation DNA sequencing technologies being developed to make inexpensive whole genome sequencing a reality. A review of the potential of this emerging nanotechnology was published recently in Nature Nanotechnology [abstract]. The full text of the review “Nanopore sensors for nucleic acid analysis” has been made available by the authors for down-loading. Nanopores and other third generation sequencing technologies sequence single molecules of DNA in real time. Single molecules of DNA are pulled through a nanopore of some type and changes in the ionic current, dependent on whether an A, G, C, or T nucleotide is passing through the pore, are recorded. The review discusses the different types of nanopore that have been tried, both biological and solid-state, and the challenges encountered, such as reducing the speed at which the DNA molecule transits the nanopore, and improving sensitivity.

Research done by scientists at Harvard and MIT and published in Nature [abstract, free authors' manuscript deposited in PubMedCentral] showed that a graphene sheet one or two atomic layers thick could form an electrode separating two liquid reservoirs so that current from ions passing through a nanopore in the graphene sheet could be measured, and the current blockade seen when DNA molecules passed through the pore indicated it should be possible to resolve individual nucleotides with an insulating membrane this thin. From a Harvard Gazette article by Michael Rutter “Graphene may help speed up DNA sequencing“:

… By drilling a tiny pore just a few nanometers in diameter, called a nanopore, in the graphene membrane, the researchers were able to measure exchange of ions through the pore and demonstrate that a long DNA molecule can be pulled through the graphene nanopore just as a thread is pulled through the eye of a needle.

“By measuring the flow of ions passing through a nanopore drilled in graphene we have demonstrated that the thickness of graphene immersed in liquid is less then 1 nm thick, or many times thinner than the very thin membrane which separates a single animal or human cell from its surrounding environment,” says lead author Slaven Garaj, a physics research associate at Harvard. “This makes graphene the thinnest membrane able to separate two liquid compartments from each other. The thickness of the membrane was determined by its interaction with water molecules and ions.” …

“Although the membrane prevents ions and water from flowing through it, the graphene membrane can attract different ions and other chemicals to its two atomically close surfaces. This affects graphene’s electrical conductivity and could be used for chemical sensing,” says co-author Jene Golovchenko, the Rumford Professor of Physics and Gordon McKay Professor of Applied Physics at Harvard, whose pioneering work started the field of artificial nanopores in solid-state membranes. “I believe the atomic thickness of the graphene makes it a novel electrical device that will offer new insights into the physics of surface processes and lead to a wide range of practical application, including chemical sensing and detection of single molecules.” …

When the researchers added long DNA chains in the liquid, they were electrically pulled one by one through the graphene nanopore. As the DNA molecule threaded the nanopore, it blocked the flow of ions, resulting in a characteristic electrical signal that reflects the size and conformation of the DNA molecule. …

As a DNA chain passes through the nanopore, the nucleobases, which are the letters of the genetic code, can be identified. But a nanopore in graphene is the first nanopore short enough to distinguish between two closely neighboring nucleobases.…

More recently another group at Harvard has integrated nanowire field-effect transistors with a solid-state nanopore to achieve rapid, sensitive detection of the very small currents created as DNA molecules zip through the nanopore. From a Harvard Gazette story by Peter Reuell “Reading life’s building blocks“:

Scientists are one step closer to a revolution in DNA sequencing, following the development in a Harvard lab of a tiny device designed to read the minute electrical changes produced when DNA strands are passed through tiny holes — called nanopores — in an electrically charged membrane.

As described in Nature Nanotechnology [abstract, free full text provided by authors] on Dec. 11, a research team led by Charles Lieber, the Mark Hyman Jr. Professor of Chemistry [and also winner of the 2001 Feynman Prize in Nanotechnology-Experimental], have succeeded for the first time in creating an integrated nanopore detector, a development that opens the door to the creation of devices that could use arrays of millions of the microscopic holes to sequence DNA quickly and cheaply.

First described more than 15 years ago, nanopore sequencing measures subtle electrical current changes produced as the four base molecules that make up DNA pass through the pore. By reading those changes, researchers can effectively sequence DNA.

But reading those subtle changes in current is far from easy. A series of challenges — from how to record the tiny changes in current to how to scale up the sequencing process — meant the process has never been possible on a large scale. Lieber and his team, however, believe they have found a unified solution to most of those problems.

“Until we developed our detector, there was no way to locally measure the changes in current,” Lieber said. “Our method is ideal because it is extremely localized. We can use all the existing work that has been done on nanopores, but with a local detector we’re one step closer to completely revolutionizing sequencing.”

The detector developed by Lieber and his team grew out of earlier work on nanowires. Using the ultra-thin wires as a nanoscale transistor, they are able to measure the changes in current more locally and accurately than ever before.

“The nanowire transistor measures the electrical potential change at the pore and effectively amplifies the signal,” Lieber said. “In addition to a larger signal, that allows us to read things much more quickly. That’s important because DNA is so large [that] the throughput for any sequencing method needs to be high. In principle, this detector can work at gigahertz frequencies.”

The highly localized measurement also opens the door to parallel sequencing, which uses arrays of millions of pores to speed the sequencing process dramatically.

In addition to the potential for greatly improving the speed of sequencing, the new detector holds the promise of dramatically reducing the cost of DNA sequencing, said Ping Xie, an associate of the Department of Chemistry and Chemical Biology and co-author of the paper describing the research. …

“Right now, we are limited in our ability to perform DNA sequencing,” Xie said. “Current sequencing technology is where computers were in the ’50s and ’60s. It requires a lot of equipment and is very expensive. But just 50 years later, computers are everywhere, even in greeting cards. Our detector opens the door to doing a blood draw and immediately knowing what a patient is infected with, and very quickly making treatment decisions.”

Rapid, inexpensive DNA sequencing and other nanotechnology-based innovations in drug-delivery and tissue regeneration may transform health care in the coming decade.
—James Lewis

A team led by Michelle Y. Simmons, who spoke on “Atomic-scale device fabrication in silicon” at the 2007 Productive Nanosystems: Launching the Technology Roadmap conference, which introduced the Technology Roadmap for Productive Nanosystems, has succeeded in the atomically precise placement of a transistor consisting of a single atom of phosphorous between source and drain electrodes and gate electrodes all made from phosphorous wires only a few atoms wide. A YouTube video illustrating this working transistor of a single atom of phosphorous placed with atomic precision on a silicon crystal includes an STM image that shows the single phosphorous atom placed several tens of rows of silicon atoms from source and drain electrodes of phosphorous that appear to be about 10 rows of atoms wide. To manufacture the phosphorous transistor and electrodes, a scanning tunneling microscope was used to remove precisely determined hydrogen atoms from the passivating layer covering a silicon crystal to form a mask that was then used to apply phosphorous atoms to the vacancies created. An overlay of silicon atoms then preserved these phosphorous nanostructures. The accomplishment is described in a NY Times article by John Markoff, which describes both the place of this work in the progression of Moore’s Law and its potential for a new generation of quantum computers: “Physicists Create a Working Transistor From a Single Atom“:

Australian and American physicists have built a working transistor from a single phosphorus atom embedded in a silicon crystal.

The group of physicists, based at the University of New South Wales and Purdue University, said they had laid the groundwork for a futuristic quantum computer that might one day function in a nanoscale world and would be orders of magnitude smaller and quicker than today’s silicon-based machines. …

“Their approach is extremely powerful,” said Andreas Heinrich, an I.B.M. physicist. “This is at least a 10-year effort to make very tiny electrical wires and combine them with the placement of a phosphorous atom exactly where they want them.”

He said the research was a significant step toward making a functioning quantum computing system. However, whether quantum computing will ever be harnessed for useful tasks remains uncertain, and the researchers also noted that their work demonstrated the fundamental limits that today’s computers would be able to shrink to.

“It shows that Moore’s Law can be scaled toward atomic scales in silicon,” said Gerhard Klimeck, professor of electrical and computer engineering at Purdue, referring to the rate at which computing gets faster and cheaper. “The technologies for classical computing can survive to the atomic scale.”

The results were published in Nature Nanotechnology [abstract]. At least for the moment (February 19, 2012), the full text is available without charge. Also available in the same issue is a commentary by Gabriel P. Lansbergen “Nanoelectronics: Transistors arrive at the atomic limit“, which gives additional background and details on this accomplishment.

… Single-atom transistors represent the ultimate limit in solid-state device miniaturization, but they are also interesting for another reason. Deterministically positioned single-dopant atoms in silicon, electrically addressable by metallic leads, are at the heart of a number of promising proposals for quantum-information-processing devices3. The long coherence and relaxation times associated with single dopants make them very attractive candidates for quantum-device architectures.

The atom-by-atom fabrication technique developed by Simmons and co-workers therefore fulfills a long-standing need for a method that is capable of atomic-scale device fabrication in silicon. And although the technique is not directly applicable on an industrial scale, it does bring the development of truly atomistic electronics — and the possibilities they offer — into the experimental realm.

This latest accomplishment from Prof. Simmons and her collaborators follows swiftly on their recent demonstration published just last month in Science [abstract], that Ohms law holds for nanowire only four phosphorous atoms wide. From the Purdue University news service “Down to the wire for silicon: Researchers create a wire 4 atoms wide, 1 atom tall“:

The smallest wires ever developed in silicon – just one atom tall and four atoms wide – have been shown by a team of researchers from the University of New South Wales, Melbourne University and Purdue University to have the same current-carrying capability as copper wires.

Experiments and atom-by-atom supercomputer models of the wires have found that the wires maintain a low capacity for resistance despite being more than 20 times thinner than conventional copper wires in microprocessors.

The discovery, which was published in this week’s journal Science, has several implications, including:

• For engineers it could provide a roadmap to future nanoscale computational devices where atomic sizes are at the end of Moore’s law. The theory shows that a single dense row of phosphorus atoms embedded in silicon will be the ultimate limit of downscaling.
• For computer scientists, it places donor-atom based silicon quantum computing closer to realization.
• And for physicists, the results show that Ohm’s Law, which demonstrates the relationship between electrical current, resistance and voltage, continues to apply all the way down to an atomic-scale wire.

…

Although the path from this laboratory demonstration to a practical technology is not yet clear, as emphasized above by the researchers themselves and commentators, the progress at Zyvex Labs (and elsewhere) that we cited in Oct. 2010 in this basic technology of using an STM for atomically precise lithography holds hope that a convergence of manufacturing technology and demonstrated prototypes will not be too distant.
—James Lewis