This 3-D print shows a DNA-based structure designed to test a critical assumption -- that such objects could be realized, as designed, with subnanometer precision. This object is a relatively large, three-dimensional DNA-based structure, asymmetrical to help determine the orientation, and incorporating distinctive design motifs. Subnanometer-resolution imaging with low-temperature electron microscopy enabled researchers to map the object -- which comprises more than 460,000 atoms -- with subnanometer-scale detail. (Credit: Dietz Lab, TU Muenchen)

Before this year the best way to build complex 3D nanostructures from DNA was to use scaffolded DNA origami (see, for example, this post). Last May scientists at the Wyss Institute introduced a DNA tile method for fabricating complex DNA objects that was much faster and much less expensive, and just two weeks ago we posted news that they had extended this method to make arbitrarily complex 3D DNA nanostructures from DNA bricks. Now scientists at the Technische Universität München have published two papers documenting major enhancements to scaffolded DNA origami. From “Reality check for DNA nanotechnology“:

Two major barriers to the advancement of DNA nanotechnology beyond the research lab have been knocked down. This emerging technology employs DNA as a programmable building material for self-assembled, nanometer-scale structures. Many practical applications have been envisioned, and researchers recently demonstrated a synthetic membrane channel made from DNA. Until now, however, design processes were hobbled by a lack of structural feedback. Assembly was slow and often of poor quality. Now researchers led by Prof. Hendrik Dietz of the Technische Universitaet Muenchen (TUM) have removed these obstacles.

One barrier holding the field back was an unproven assumption. Researchers were able to design a wide variety of discrete objects and specify exactly how DNA strands should zip together and fold into the desired shapes. They could show that the resulting nanostructures closely matched the designs. Still lacking, though, was the validation of the assumed subnanometer-scale precise positional control. This has been confirmed for the first time through analysis of a test object designed specifically for the purpose. A technical breakthrough based on advances in fundamental understanding, this demonstration has provided a crucial reality check for DNA nanotechnology.

In a separate set of experiments, the researchers discovered that the time it takes to make a batch of complex DNA-based objects can be cut from a week to a matter of minutes, and that the yield can be nearly 100%. They showed for the first time that at a constant temperature, hundreds of DNA strands can fold cooperatively to form an object — correctly, as designed — within minutes. Surprisingly, they say, the process is similar to protein folding, despite significant chemical and structural differences. “Seeing this combination of rapid folding and high yield,” Dietz says, “we have a stronger sense than ever that DNA nanotechnology could lead to a new kind of manufacturing, with a commercial, even industrial future.” And there are immediate benefits, he adds: “Now we don’t have to wait a week for feedback on an experimental design, and multi-step assembly processes have suddenly become so much more practical.” …

To test the unproven assumption of subnanometer-scale precise positional control, the TUM scientists and their collaborators at MRC Laboratory of Molecular Biology in Cambridge, UK built a large asymmetrical 3D DNA nanostructure incorporating distinctive design motifs, and then characterized its structure with low-temperature electron microscopy. The research was published recently in PNAS (abstract, open access PDF). They designed a DNA nanostructure comprising 15,328 nucleotides (more than 460,000 atoms) assembled from a 7,249-nucleotide long scaffold strand of bacteriophage DNA and 163 short staple strands. The structure formed overnight in a one-pot reaction in high yield. Cryo-electron microscopy enabled a 3D reconstruction based upon tens of thousands of individual images. The resolution of the reconstructed image was sub-nanometer but not quite atomically precise, ranging from 0.97 nm in the core of the nanostructure to 1.4 nm at the periphery. Analysis of the structure determined indicates that the structural order within the nanostructure is comparable to that of natural nanomachines. Detailed comparison of the obtained structure with the designed structure showed more variation than expected in the structure of the DNA helices formed, indicating that the densely packed design led to some unusual DNA topologies. These results indicate that an interactive strategy of designing a folded DNA structure followed by 3D structural analysis will allow construction of a rich variety of precise, complex objects. The authors conclude:

By using chemical groups attached to DNA strands or even reactive motifs formed by DNA itself, this strategy offers an attractive route to achieving complex functionalities known today only from natural nanomachines.

In a second paper just published in Science [abstract], the TUM researchers tackle a major limitation of scaffolded DNA origami: week-long reaction times as the mixture of template and staple DNA strands is very slowly cooled over a very large temperature range, and poor yields. The researchers very carefully followed the rate of structure formation for three different DNA nanostructures as reaction mixes were slowly cooled over a very broad temperature range. One DNA nanostructure was a multilayer platelike structure, one a bricklike object, and a third a gearlike object. They found that the DNA nanostructures each formed at a very narrow temperature range (of about 4° C) that was different for each DNA nanostructure. In addition, the folding was complete in as little as 15 minutes. By choosing the appropriate temperature for each DNA nanostructure, the folding could be complete at constant temperature in as little as 5 minutes. Further, folding at constant temperature greatly increased the yield of correctly folded nanostructures. For several different nanostructures, the increase in yield compared to previous protocols ranged from 7-fold to 330-fold improvement. In absolute terms, the yield of properly folded nanostructres approached 100%. The authors note that several attributes of the folding they observe with their protocols resemble the folding of proteins, despite the chemical and structural differences between proteins and DNA.

From the standpoint of DNA nanotechnology as a component of the Technology Roadmap for Productive Nanosystems, the high yield of well-folded building blocks opens the door to hierarchical assembly of larger objects. It will also greatly facilitate the process of fine-tuning the design of functional molecular machine systems incorporating complex DNA nanostructures. The respective roles to be played by DNA bricks and scaffolded DNA origami, of course, remain to be seen.
—James Lewis, PhD

(credit: Reck-Peterson Lab, Harvard Medical School)

Among the recommendations of the 2007 Technology Roadmap for Productive Nanosystems is the development of modular molecular composite nanosystems (MMCNs), such as systems in which million-atom-scale DNA frameworks are used to organize various functional molecular components in ways to accomplish specific functions, eventually including atomically precise manufacturing. A step in this direction was taken by Harvard University scientists who used a DNA origami framework as a chasis on which to assemble and test the biological molecular motors that maintain subcellular organization in eukaryotic cells through the organized transport of various molecular cargos. In cells these molecular motors dynein and kinesin transport cargos in opposite directions along a hollow 25-nm-diameter protein track—the microtubule component of the cytoskeleton. In this work, the molecular motors carried a DNA chasis cargo along microtubules for a few tens of micrometers—comparable to the length of a eukaryotic cell. “Tug-of-War in Motor Protein Ensembles Revealed with a Programmable DNA Origami Scaffold” was published online in Science last week [abstract, PDF made available by corresponding author].

The DNA chasis comprised a 12-helix bundle with six DNA double helices on the inside and six on outside of the bundle. A total of 90 unique DNA handles on the outer helices of the chasis, and complementary DNA handles on the cargo-binding domains of the dynein and kinesin motor molecules, made it possible to bind specific motor molecules to specific spots on the DNA chasis. The researchers then measured how fast and how far the DNA chasis cargoes were carried along the microtubules when different ensembles of motor molecules were attached to one DNA chasis. After determining how different number of one motor carried the cargo to one end of the microtubule and different numbers of the other motor carried the cargo to the other end of the microtubule, the researchers tried mixing both motors on one cargo chasis. Not surprisingly, in some cases no movement was observed as the two motors tugged in opposite directions. Specific cleavage of the attachments of one type of motor to the cargo released the cargo to move in the appropriate direction. In summing up their results:

Using DNA origami, we built a versatile, synthetic cargo system that allowed us to determine the motile behavior of microtubule-based motor ensembles. In ensembles of identical-polarity motors, motor number had minimal affect on directional velocity, while ensembles of opposite-polarity motors engaged in a tug-of-war resolvable by disengaging one motor species. … The system we built pro-vides a powerful platform to investigate the motile properties of any combination of identical- or opposite-polarity motors, and could also be used to investigate the role of motor regulation.

It seems likely that the system reported in this article will enable researchers to learn to regulate the movement of molecular motors carrying very diverse cargos along thick protein tracks to destinations separated by micrometers or ten of micrometers. Would such a capability contribute to the construction of useful molecular assembly lines? Could molecular motors be constructed that move cargos shorter, precisely determined distances along smaller, more precisely arranged tracks? Is this just a cute trick for learning more about biological molecular motors (after all, they do figure prominently in various serious diseases), or could this be a small step toward learning to build nanofactories?
—James Lewis, PhD

Northwestern University researchers have broken a world record by creating two new synthetic materials with the greatest amount of surface areas reported to date.

Named NU-109 and NU-110, the materials belong to a class of crystalline nanostructure known as metal-organic frameworks (MOFs) that are promising vessels for natural-gas and hydrogen storage for vehicles, and for catalysts, chemical sensing, light harvesting, drug delivery, and other uses requiring a large surface area per unit weight.

The materials’ promise lies in their vast internal surface area. If the internal surface area of one NU-110 crystal the size of a grain of salt could be unfolded, the surface area would cover a desktop. …

MOFs are composed of organic linkers held together by metal atoms, resulting in a molecular cage-like structure. The researchers believe they may be able to more than double the surface area of the materials by using less bulky linker units in the materials’ design. …

Beyond their near-term practical applications, Eric Drexler has cited MOFs as potentially useful building blocks in the molecular machine path to molecular manufacturing. Near-term applications may drive the technology development to produce more choices for molecular machine system components.
—James Lewis, PhD

Walk traffic man icon assembled by using an atomic force microscope to place molecules of green fluorescent protein (credit: Ludwig-Maximilians University)

Four years ago we cited a report by a German research group of a single molecule cut and paste technology to assemble molecular building blocks on a DNA scaffold. The advance was noteworthy because it combined self-assembly of atomically precise components with the ability to use a manipulator (an atomic force microscope) to place those components at arbitrary positions in a larger structure, analogous to the way in which we use our hands to assemble parts macroscopically. These researchers have extended this technology to arrange single protein molecules. A hat tip to ScienceDaily.com and KurzweilAI.net for pointing to this press release from Ludwig-Maximilians University in Munich “All systems go at the biofactory“:

In order to assemble novel biomolecular machines, individual protein molecules must be installed at their site of operation with nanometer precision. LMU researchers have now found a way to do just that. Green light on protein assembly!

The finely honed tip of the atomic force microscope (AFM) allows one to pick up single biomolecules and deposit them elsewhere with nanometer accuracy. The technique is referred to as Single-Molecule Cut & Paste (SMC&P), and was developed by the research group led by LMU physicist Professor Hermann Gaub. In its initial form, it was only applicable to DNA molecules. However, the molecular machines responsible for many of the biochemical processes in cells consist of proteins, and the controlled assembly of such devices is one of the major goals of nanotechnology. A practical method for doing so would not only provide novel insights into the workings of living cells, but would also furnish a way to develop, construct and utilize designer nanomachines.

In a major step towards this goal, the LMU team has modified the method to allow them to take proteins from a storage site and place them at defined locations within a construction area with nanometer precision. “In liquid medium at room temperature, the “weather conditions” at the nanoscale are comparable to those in a hurricane,” says Mathias Strackharn, first author of the new study. Hence, the molecules being manipulated must be firmly attached to the tip of the AFM and held securely in place in the construction area.

The forces that tether the proteins during transport and assembly must also be weak enough not to cause damage, and must be tightly controlled. To achieve these two goals, the researchers used a combination of antibodies, DNA-binding “zinc-finger” proteins, and DNA anchors. “We demonstrated the method’s feasibility by bringing hundreds of fluorescent GFP molecules together to form a little green man, like the traffic-light figure that signals to pedestrians to cross the road, but only some micrometers high,” Strackharn explains.

With this technique, functional aspects of complex protein machines – such as how combinations of different enzymes interact, and how close together they must be to perform coupled reactions – can be tested directly. A further goal is to develop artificial multimolecular assemblies modeled on natural “cellulosomes”, which could be used to convert plant biomass into biofuels. Strackharn points out the implications: “If we can efficiently build mimics of these ‘enzymatic assembly lines’ by bringing individual proteins together, we could perhaps make a significant contribution to the exploitation of sustainable energy sources.” [abstract of research paper]

The precision achieved in this preliminary report of single-molecule cut-and-paste with proteins is about 10 nm. This is about 100-fold less precise than atomic precision. However, the AFM tip can be moved with atomic precision (0.1 nm). The lower precision seen in this preliminary demonstration is due to the long spacer used to attach the anchor DNA to the surface, so the precision can presumably be improved in future work as it becomes more important.

To use the AFM to build a structure by precisely placing GFP molecules, the Green Fluorescent Protein was fused to a zinc finger protein that binds a specific fragment of double strand DNA. This DNA fragment has a single strand overhang that binds to a single strand anchor DNA on the surface in what the authors refer to as the “unzip” geometry so that the DNA binding can be pulled apart one base pair at a time. The GFP is also fused to a short peptide fragment that will bind to an antibody fragment that is attached to the AFM tip.

The combination of DNA base pair interactions and peptide-antibody interactions allows controlled transfer of the green fluorescent protein-DNA complex from the depot to the AFM tip because only a force of 25 pN is required to separate the complex from the depot one base pair at a time, but a force of 40 pN binds the complex to the AFM tip. Lowering the AFM tip at the target position binds to the anchor DNA at the target, but because the DNA strand at the target position is in the “shear” geometry, this new DNA complex cannot be ruptured by a force of less than 60 pN, so the AFM tip can be retracted leaving the GFP complex in the new position.

Assembling the micrometer-size image of the “traffic man” from individual GFP molecules required 900 steps. Two “traffic man” icons were assembled: one using a red dye coupled to the DNA component of the complex that was assembled in the shape of the sign that means “Don’t walk,” and one using the green fluorescence of the GFP itself in the shape of the sign that means “Walk”. The fact the GFP still fluoresces shows that the forces used during the process are gentle enough to preserve the function of the protein.

This work is an important step in the biology-based folding polymer path toward designing and building complex molecular machine systems (see the Technology Roadmap for Productive Nanosystems for discussions of various paths). With the huge array of molecular machines that biology provides it should be possible to explore the capabilities of some very sophisticated systems. It is not yet clear just how precise this cut and paste system can be made, so it is premature to compare it with other proposed systems of assembling designed arrays of proteins: using DNA origami or DNA tiles as scaffolds.
—James Lewis, PhD

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

Kyoto, Japan — Expanding on previous work with engines traveling on straight tracks, a team of researchers at Kyoto University and the University of Oxford have successfully used DNA building blocks to construct a motor capable of navigating a programmable network of tracks with multiple switches. The findings, published in the January 22 online edition of the journal Nature Nanotechnology [abstract], are expected to lead to further developments in the field of nanoengineering.

The research utilizes the technology of DNA origami, where strands of DNA molecules are sequenced in a way that will cause them to self-assemble into desired 2D and even 3D structures. In this latest effort, the scientists built a network of tracks and switches atop DNA origami tiles, which made it possible for motor molecules to travel along these rail systems.

“We have demonstrated that it is not only possible to build nanoscale devices that function autonomously,” explained Dr. Masayuki Endo of Kyoto University’s Institute for Integrated Cell-Material Sciences (iCeMS), “but that we can cause such devices to produce predictable outputs based on different, controllable starting conditions.”

The team, including lead author Dr. Shelley Wickham at Oxford, expects that the work may lead to the development of even more complex systems, such as programmable molecular assembly lines and sophisticated sensors.

“We are really still at an early stage in designing DNA origami-based engineering systems,” elaborated iCeMS Prof. Hiroshi Sugiyama. “The promise is great, but at the same time there are still many technical hurdles to overcome in order to improve the quality of the output. This is just the beginning for this new and exciting field.”

Courtesy Sugiyama Lab, Kyoto University iCeMS

A depiction of a DNA origami tile with a built-in network of tracks. The DNA engine or motor, in red, can be programmed to navigate a series of junctions to reach one of four desired end points.

Perhaps the next step is to have multiple addressable DNA motors bring different components together to be joined?
—James Lewis

The authors begin with the observation that, despite “remarkable progress” in synthesizing molecular switches, there have been only few and very rudimentary examples of harvesting useful work from such molecular switches. They then ask whether only incremental progress will be necessary for artificial molecular machines to achieve the levels of function so elegantly achieved by biological molecular machines, or whether some paradigm shift in thinking will be necessary (they believe the latter).

The fundamental theory of molecular machines is applied to two questions. (1) Can artificial molecular machines be developed to manipulate or chemically transform other molecular or nanoscale structures? (2) Can artificial molecular machines be assembled into integrated systems that work together to manipulate or fabricate structures at the meso- and macroscopic levels? The overall conclusion of these authors with respect to these two questions is optimistic:

Indeed, nanoscale-based machinery has been envisaged ever since the days of Feynman and today the Feynman’s Grand Prize offers a $250,000 reward to the first persons to create a nanoscale robotic arm, capable of precise positional control. While, in pursuit of this goal, the “top-down” fabrication strategies have so far failed rather dismally, we are convinced that a “bottom-up” approach, utilizing AMMs [artificial molecular machines], can deliver. Engineering a macromolecular architecture capable of robotic function will no doubt be a considerable synthetic challenge. We feel, however, that the time is ripe for such an undertaking—for instance, by combining AMMs with the DNA-origami materials, such that the former would provide the actuation within precisely folded DNA nanoscaffolds of the latter.

A major focus of this tutorial review is to describe the recently developed theoretical concepts “that distinguish simple molecular switches from fully fledged molecular machines.” Simple molecular switches differ from familiar macroscopic switches in that the switching between the states of the switch is driven by thermal noise. To advance from simple molecular switches to molecular machines, it must be possible to drive chemical reactions uphill, away from equilibrium, as do biological motor molecules. This can be accomplished by using molecular switches to alter the energy profile of the reaction by first lowering the energy of the intermediate to be less than the energy of the starting material, and then switching again to raise the energy of the intermediate above that of the product, and finally switching again to reset the system to the original energy profile. Switching makes each molecular transformation along the way spontaneous, but the end result is shifted way from the equilibrium without switching.

The authors give the example of doubly stable bistable rotaxanes—dumbbell-shaped molecules in which an electrochemical input can move reactants to different positions along the central part of the dumbbell to alter an energy profile and drive a reaction uphill. An example is given of a molecule that can be switched by an oxidation-reduction event between contracted and extended states. If such a molecule is attached to a molecular spring, then the extended form of the molecule could store energy in the spring molecule. If the architecture of the device as a whole allows the spring to be detached from the oxidation-reduction switch, then the energy stored in the spring can be harvested to do external work. Thus an oxidation-reduction switch becomes part of a simple molecular motor.

Having considered how to extract external work from externally switchable molecules, the authors consider how sufficient energy to perform macroscopic work could be harvested from mesoscopic arrays of AMMs. They note that in biological systems molecular motors are organized spatially and synchronized to act together, and consider approaches to fabricate such arrays through self-assembly. They cite metal oxide frameworks as one potentially promising type of scaffolding that might be used to array AMMs.

The brief roadmap presented in this tutorial review outlines the challenges and opportunities involved in transforming simple molecular switches into AMMs. The authors are optimistic:

On the horizon lie new types of “mechanized” enzyme-like mimicks, addressable nanomaterials, nanorobots, and possibly more into the bargain.

Physicist Richard Feynman in his famous 1959 talk, “Plenty of Room at the Bottom,” described the precise control at the atomic level promised by molecular machines of the future. More than 50 years later, synthetic molecular switches are a dime a dozen, but synthetically designed molecular machines are few and far between.

Northwestern University chemists recently teamed up with a University of Maine physicist to explore the question, “Can artificial molecular machines deliver on their promise?” Their provocative analysis provides a roadmap outlining future challenges that must be met before full realization of the extraordinary promise of synthetic molecular machines can be achieved.

The tutorial review is published by the journal Chemical Society Reviews.

The senior authors are Sir Fraser Stoddart, Board of Trustees Professor of Chemistry, and Bartosz A. Grzybowski, the K. Burgess Professor of Physical Chemistry, both in Northwestern’s Weinberg College of Arts and Sciences, and Dean Astumian, professor of physics at the University of Maine. (Grzybowski is also professor of chemical and biological engineering in the McCormick School of Engineering and Applied Science.)

One might ask, what is the difference between a switch and a machine at the level of a molecule? It all comes down to the molecule doing work.

“A simplistic analogy of an artificial molecular switch is the piston in a car engine while idling,” explains Ali Coskun, lead author of the paper and a postdoctoral fellow in Stoddart’s laboratory. “The piston continually switches between up and down, but the car doesn’t go anywhere. Until the pistons are connected to a crankshaft that, in turn, makes the car’s wheels turn, the switching of the pistons only wastes energy without doing useful work.”

Astumian points out that this analogy only takes us part of the way to understanding molecular machines. “All nanometer-scale machines are subject to continual bombardment by the molecules in their environment giving rise to what is called ‘thermal noise,’” he cautions. “Attempts to mimic macroscopic approaches to achieve precisely controlled machines by minimizing the effects of thermal noise have not been notably successful.”

Scientists currently are focused on a chemical approach where thermal noise is exploited for constructive purposes. Thermal “activation” is almost certainly at the heart of the mechanisms by which biomolecular machines in our cells carry out the essential tasks of metabolism. “At the nanometer scale of single molecules, harnessing energy is as much about preventing unwanted, backward motion as it is about causing forward motion,” Astumian says.

In order to fulfill their great promise, artificial molecular machines need to operate at all scales. A single molecular switch interfaced to its environment can do useful work only on its own tiny scale, perhaps by assembling small molecules into chemical products of great complexity. But what about performing tasks in the macroscopic world?

To achieve this goal, “there is a need to organize the molecular switches spatially and temporally, just as in nature,” Stoddart explains. He suggests that “metal-organic frameworks may hold the key to this particular challenge on account of their robust yet highly integrated architectures.”

What is really encouraging is the remarkable energy-conversion efficiency of artificial molecular machines to perform useful work that can be greater than 75 percent. This efficiency is quite spectacular when compared to the efficiency of typical car engines, which convert only 20 to 30 percent of the chemical energy of gasoline into mechanical work, or even of the most efficient diesel engines with efficiencies of 50 percent.

“The reason for this high efficiency is that chemical energy can be converted directly into mechanical work, without having to be first converted into heat,” Grzybowski says. “The possible uses of artificial molecular machines raise expectations expressed in the fact that the first person to create a nanoscale robotic arm, which shows precise positional control of matter at the nanoscale, can claim Feynman’s Grand Prize of $250,000.”

• What will be the next great revolution in the material basis of civilization?
• How can we establish reliable knowledge about key aspects of such technologies?

From the news release, aptly titled “The next technological revolution?“:

The key to tackling some of our planet’s greatest challenges may be found in the laws of physics and methods of engineering, as opposed to any specific technological innovation.

Speaking at the inaugural public lecture of the Oxford Martin Programme on the Impacts of Future Technology, Dr Eric Drexler said there is a compelling case for the viability of atomically precise manufacturing. This is the process of building structures, tools and machines starting at the molecular level, with atomic precision, to address challenges such as rising greenhouse gases and energy production for our growing population.

In a talk entitled “Exploring a Timeless Landscape: Physical Law and the Future of Nanotechnology”, pioneering nanotechnology researcher Dr. Drexler invited the audience to consider the intriguing possibility of nano-level manufacture of macro-level products. Such a process, if achieved, would be the next great revolution in the material basis of civilization, offering high-performance components, materials or systems and accelerated productivity. …

Those who have read Drexler’s 1988 essay on exploratory engineering and the 2007 Technology Roadmap for Productive Nanosystems will be familiar with the main arguments presented in the talk. Dr. Drexler’s conclusions about the development of atomically precise manufacturing were:

• We now have ample scientific knowledge. Rather than additional breakthroughs we need component design.
• Molecular experiments are fast and inexpensive by ordinary engineering standards.
• Advances in fabrication methods will yield faster more predictable results, accelerating progress.

Dr. Drexler left the audience to consider whether the advent of atomically precise manufacturing meant that in preparing for the 21st century we should expect scarcity and conflict or something radically different, and whether we could change the conversation in the world about the future incrementally in a well-grounded way.

The Oxford Martin Programme has made the abstract available, which includes a link to a Youtube video of the lecture “Timeless Landscape: Physical Law and the Future of Nanotechnology“.

A decade ago, University of Oregon chemist James E. Hutchison wrote an invited article in Chemical & Engineering News in which he envisioned “a generalized roadmap for the future design and development of green nanoscience materials.”

That roadmap has grown up and is now in front of chemistry leaders worldwide with the publication of “Green Nanotechnology Challenges and Opportunities.” The new “white paper” on the potential of incorporating benign chemistry practices was co-written by Hutchison. The American Chemical Society’s Green Chemistry Institute issued the document, which is freely available at www.acs.org/greenreport.

…

“The roots of green nano are really deep here in Oregon,” said Hutchison, who holds the Lokey-Harrington Chair in Chemistry at the UO. “This report mirrors the strategy that we have had for several years now. This is the way that things are going to be done. The report addresses the need for commercialization, for new policies — a new science for addressing our societal needs. It’s been 10 years in coming, but we are at the table now.”

The report outlines the promise of green nanotechnology, which promotes the design of useful particles thousands of times smaller than the width of a human hair in a way that reduces or eliminates waste or the production of hazardous substances. It also spells out what actions need to be undertaken by the various stakeholders, Hutchison said.

When successfully implemented, green nanotechnology could lead to a revitalized and sustainable U.S. chemical and materials manufacturing base, the white paper says. Nanoparticles could well find their ways into medicine, electronics, energy production and other industries.

“Green Nanotechnology Challenges and Opportunities” presents examples of both encouraging success in meeting the challenges of near-term nanoparticle development and reasons for concern that inept government regulation will retard progress.

A solid success is the development of sensitive assays for the biological effects of nanoparticle to be used to guide research and development of nanoparticles for applications. The combination of the embryonic zebrafish model with precisely engineered gold nanoparticles means that the effect of specific changes to charge, surface chemistry, and particle size can be investigated for subtle biological effects.

An example of the challenges yet to be overcome is the case of Dune Sciences. This company licensed a promising nanotechnnology innovation to permanently attach silver nanoparticles to surfaces so that commercial antimicrobial applications of silver nanoparticles could be developed without the worry of potentially toxic silver nanoparticles escaping into the environment. Unfortunately no path could be found through the EPA regulatory maze to register the product, despite the evident fact that the proposed product was safer than what was already on the market. This impasse prevented the company from securing funding and necessitated putting development of the product on hold.

The report also presents a brief analysis of the different barriers to developing nanotechnology in the US and in China that is worth a look.

Given Foresight’s interest in the long-term development of atomically precise productive nanosystems as a future manufacturing technology, with both its much greater potential benefits and its potentially more complex regulatory issues, the path forward being blazed by green nanotechnology is worth following.