Whether you’re following the development or just interested in the possible impact of nanotechnology, a new report published by the American Chemical Society (ACS) in the journal ACS Nano, titled Nanomaterials in the Construction Industry: A Review of Their Applications and Environmental Health and Safety Considerations is a comprehensive look at the future of nanotechnology in the materials used by the construction industry AND their potential impact on health and the environment. A lengthy abstract is available at the above URL; the full text of the report requires subscription or purchase.

The report was prepared by scientists at Rice University (Texas, USA) and the University of California Los Angeles (USA). Its combination of a review of applications with a realistic approach to potential problems makes this report a standout. While the language is at times technical (the target audience is for people familiar with the field), it’s easy to understand the overall picture:

Nanomaterials will be extensively incorporated in construction materials. Nanomaterials will make them stronger, lighter, more flexible, and endow some materials with unusual or even extraordinary properties. Overall the application of nanomaterials provides a major opportunity for more energy conserving and environmentally friendly materials – as long as that is made a top priority.

Examples of uses for manufactured nanomaterials (MNMs)
[Taken from Table 1 of Nanomaterials in the Construction Industry]

Carbon Nanotubes
Concrete Mechanical durability, crack prevention
Ceramics Enhanced mechanical and thermal properties
MEMS Real-time structural health monitoring
Solar Cell Effective electron mediation
Silicon Dioxide Nanoparticles
Concrete Reinforcement in mechanical strength
Ceramics Coolant, light transmission, fire resistance
Windows Flame proofing, anti-reflection
Titanium Dioxide Nanoparticles
Cement Rapid hydration, increased degree of hydration, self-cleaning
Windows Superhydrophilicity, anti-fogging, fouling-resistance
Solar Cell Non-utility electricity generation
Iron Oxide Nanoparticles
Concrete Increased compressive strength, abrasion resistance
Copper Nanoparticles
Steel Weldability, corrosion resistance, formability
Silver Nanoparticles
Coating/Paints Biocidal activity

Source: American Chemical Society

On the other hand, nanomaterials either in raw form or in the combination with traditional construction materials will become prevalent world-wide. Insofar as these materials have toxic or environmentally damaging properties – and we already know that some of them do – this new exposure at massive scale will probably create dangerous situations (or worse).

Some MNMs could be considered as potential emerging pollutants because their environmental release is currently not regulated despite growing concerns about the associated risks to public and environmental health. Once in the environment, MNMs may undergo diverse physical, chemical, and biological transformations that change their properties, impact, and fate. Thus, a holistic MNM lifecycle exposure profiling is essential to evaluate potential impacts to human and ecosystem health, as well as to mitigate unnecessary risks.

The report stresses the importance of understanding the health and environmental impact of using nanomaterials in construction from all points in the ‘life cycle’ of the materials:

- Creation and transport of the raw (nano)components
- The manufacturing process
- Distribution and application in the construction industry
- Long-term degradation
- Final demolition and disposal.

Without taking into to account the dangers present at each point along the cycle (and they will vary considerably among the different materials), we will not have a profile accurate enough to provide guidance for regulation, prevention, troubleshooting and emergency procedures.

Perhaps the best known example of the additive process is the Hewlett-Packard 3-D printer, or as it is now called: Designjet 3D. Announced in January of 2010 to considerable hoopla, it’s just now coming to market at the popular price of about $17,000 (which is actually a lot cheaper than heavy-duty commercial versions of similar technology). It uses a thermoplastic (ABS) as the construction material and as controlled by a computer with Computer Assisted Design (CAD) software, it can create objects by spraying layer after layer of the plastic to build up a complete shape. Its immediate use is for prototyping designs. The idea sounds neat, if somewhat like science fiction. However, the fact is additive layer manufacturing (ALM or often just AM) has many forms and is slowly but surely becoming a factor in the world of commercial manufacturing.

The reasons for the rise in popularity start with economics: There is much less waste. On average, about 26 times less waste of material than standard manufacturing. This is related to a second big reason for popularity: The high degree of control over the process. By constructing things layer by layer to very exact specifications, components can be built that are impossible with traditional methods. This leads to a third reason for popularity: Designers and engineers are freer to use their imagination. After all, additive layer manufacturing’s first tasks were to make prototypes. AM is very good at making one-of-a-kind pieces, for example, artificial hip joints for specific people. All this control and freedom does have a drawback, AM processes are not very robust, that is the precision required is difficult to maintain. The mechanics are finicky and difficult to calibrate. The hard part for using AM on commercial quantity production for standard metallic or plastic components is the need to make it less delicate.

With nanotechnology, however, working with extreme precision at very small scale is the name of the game. Nanomanufacturing is already built on the foundation of very complex and ‘delicate’ machinery – marrying it with additive layer manufacturing at its present level of sophistication seems like a natural fit.

Researchers are working at combining high-performance polymers (such as polyether ether ketone, or PEEK) with carbon nanotubes. The hope is to develop AM ‘printing’ techniques that combine growing carbon nanotubes within the material in aligned formation. In short, the goal is to embed the carbon nanotube structures to perform electronic functions such as sensing and communications. Most AM techniques involve the spraying or deposition of very fine-grain particles, which are then burned or manipulated with high-powered lasers, so it’s no surprise AM companies are working with makers of nanoparticles to experiment with improved composite construction, or to add electrical properties.

The combination of additive manufacturing and nanotechnology falls into the domain of ‘emerging technologies.’ There is a perceived need to provide manufacturing techniques for some kinds of nanotechnology that are between the self-assembly envisioned at the molecular level and the traditional techniques applied to micron (or larger) scale materials. As far back as 2004 (practically ancient history in the nanotech business), a conference on Advanced Technology and the Future of American Technology came to the conclusion:

Highly miniaturized, functional, and efficient electronics devices, and precise and selective biomolecular materials are part of this future. At the same time, it is not yet well known how to manufacture nanomaterials and how to integrate nano- and large-scale manufacturing. Advancing these developments depends on the ability to foster multidisciplinary interconnections between researchers in a range of scientific and engineering disciplines, business managers, policy makers, and educators.

[Source: Georgia Tech]

What is called for could be the use of nanoparticles within the composites of additive manufacturing.

For more background on additive manufacturing, I’d recommend The rise of additive manufacturing at the Engineer (UK).

The first announcement sort of fits the battle metaphor. It’s characterized as ‘zapping nanobubbles.’ …Researchers at Rice University (Houston, USA) have developed a technique for treating cancer cells – one at a time if appropriate – by using gold nanoparticles. The nanoparticles are targeted for a specific type of cancer, where they attach to individual cells. Then a laser device, set to a specific frequency, causes the gold nanoparticles to heat causing either a (nano)bubble inside the cancer cell or exploding it (zapping).

“Single-cell targeting is one of the most touted advantages of nanomedicine, and our approach delivers on that promise with a localized effect inside an individual cell,” said Rice physicist Dmitri Lapotko, the lead researcher on the project. “The idea is to spot and treat unhealthy cells early, before a disease progresses to the point of making people extremely ill.”

[Source: EurekAlert]

The technique is not only good for an onco-shooting gallery. It can also be used for diagnosis because the nanobubbles are highly visible to microscopes. The researchers refer to this as a ‘theranostic’ opportunity – combining diagnostics followed immediately by therapy. The technique has been tested on human cancer cells. The next steps are trials of various methods of application.

The second announcement is less dramatic. It involves using nanoparticles to cross mucus barriers. That’s less dramatic, but it’s an important achievement. The human body has many organs with natural mucus barriers – the stomach, intestines, lungs, eyes, throat, cervix – some of which are nearly impermeable to traditional drug chemistry. The nanoparticles developed by the Johns Hopkins School of Medicine (Maryland, USA) have a special outer layer of polyethylene glycol (commercially, Carbowax), which makes it possible for the particles to penetrate mucus membranes with ease. The nanoparticles have been created with an inner layer of polysebacic acid, which can hold a variety of drug or genetic molecules, making the particles a drug delivery system that can be targeted for specific diseases. Better yet, the nanoparticles are designed to release their drug cargo as they biodegrade. In effect, the dissolving of the particles is the timer for release of the drugs, and when that’s over, the nanoparticle compounds are flushed out with normal bodily systems.

The original target for these nanoparticles is cystic fibrosis, which is notorious for creating unusually thick and sticky mucus in the lungs and gut.

The team’s work was reported recently in the Proceedings of the National Academy of Sciences. Hanes’ collaborators included cystic fibrosis expert Pamela Zeitlin, a professor of pediatrics at the Johns Hopkins School of Medicine and director of pediatric pulmonary medicine at the Johns Hopkins Children’s Center.

“Cystic fibrosis mucus is notoriously thick and sticky and represents a huge barrier to aerosolized drug delivery,” she said. “In our study, the nanoparticles were engineered to travel through cystic fibrosis mucus at a much greater velocity than ever before, thereby improving drug delivery. This work is critically important to moving forward with the next generation of small molecule and gene-based therapies.”

[Source: Nanotechnology Today]

This use of nanoparticles has many potential applications, some of which are in development.

The technique uses dye to color (tag) the cancer cells fluorescent green (which makes them more visible to a microscope), then magnetic nanoparticles that are dyed red are introduced, which attach themselves to the cancer cells. Once attached, the cancer cells can be located and manipulated with magnetic equipment. This method makes it possible to filter travelling cancer cells from the bloodstream or peritoneal fluids, which would reduce the occurrence of cancer spreading (metastasizing) from the original location.

We are primarily interested in developing an effective method to reduce the spread of ovarian cancer cells to other organs ,” said John McDonald, professor at the the School of Biology at the Georgia Institute of Technology and chief research scientist at the Ovarian Cancer Institute.

“Often, the lethality of cancers is not attributed to the original tumor but to the establishment of distant tumors by cancer cells that exfoliate from the primary tumor,” said Scarberry [co-author of the study]. “Circulating tumor cells can implant at distant sites and give rise to secondary tumors. Our technique is designed to filter the peritoneal fluid or blood and remove these free floating cancer cells, which should increase longevity by preventing the continued metastatic spread of the cancer.”

[Source: Georgia Tech]

This study, furthering the work done in 2008 with mice blood, has demonstrated the same ability with human blood. The next step is to work with live animals (mice) to see if the technique significantly reduces the risk of metastasization.

Pint grew his carbon nanotubes using the chemical vapor deposition (CVD) technique, which starts with a layer of catalytic metal nanoparticles. The size of these particles helps determine the size of the carbon nanotubes. The layer of catalyst (a substrate) is heated to 700C and two gasses are introduced, one is a process gas (ammonia, nitrogen, or hydrogen) and the other a carbon containing gas (acetylene, ethylene, ethanol, or methane). From these gases, carbon nanotubes grow at the sites of the metal catalyst. Typically the catalyst metal stays attached to the tips of the growing nanotubes, or remains at the base. However, Pint found that by etching the nanotubes with a mixture of hydrogen gas and water vapor, the bonds of the metal catalyst are loosened. When the nanotubes are ‘stamped’ (pressed onto another surface), they adhere to the new surface, leaving behind the catalyst.

The nanotubes stick to a surface thanks to something called the Van der Waals forces. Named after the Dutch scientist Johannes van der Waals, these forces are the attraction or repulsion between molecules, or within a molecule, at the quantum level. This relatively weak bond is different than chemical bonds created by shared ions, or bonds created by electron sharing covalence. Weak though they may be, Van der Waals forces have interesting effects, for example, the gecko (a lizard) can climb glass windows because it has millions of microscopic hairs on its feet, which generate a Van der Waals bond with surfaces it climbs. Similarly with carbon nanotubes, they ‘adhere’ to surfaces with Van der Waals forces.

Pint’s work with the CVD technique has led to the research paper on the use of metallic nanoparticles of controlled size for the carbon nanotube catalyst. The discovery of a technique for making nanotubes adhere to surfaces has led to the ability to easily create patterns – rows, crosses – of nanotubes. This is a key property in nanotube manufacturing processes and should be readily scalable for commercial purposes.

Pint is primary author of the research paper, which also details a way to quickly and easily determine the range of diameters in a batch of nanotubes grown through chemical vapor deposition (CVD). Common spectroscopic techniques are poor at seeing tubes bigger than two nanometers in diameter – or most of the nanotubes in the CVD “supergrowth” process.

“This is important since all of the properties of the nanotubes – electrical, thermal and mechanical – change with diameter,” he said. “The best thing is that nearly every university has an FTIR (Fourier transform infrared) spectrometer sitting around that can do these measurements, and that should make the process of synthesis and application development from carbon nanotubes much more precise.”

[Source: EurekAlert]

From the standpoint of the ongoing (or is it onrushing?) advance of practical applications for nanotechnology, really interesting indeed.

The key to this research was the discovery that combining two different nanoparticles – one to find and adhere to the cancerous cells and the other to kill the cells – actually worked. Typically nanoparticles in the bloodstream have a hard time staying active, either because they break down, or because the body’s own defense mechanisms, immune cells called mononuclear phagocytes, remove them. By working two nanoparticles in tandem, the researchers were able to improve the amount of time the ‘cocktail’ stays active in the bloodstream, meaning the longer time the particles have to reach the target cancer.

“This study represents the first example of the benefits of employing a cooperative nanosystem to fight cancer,” said Michael Sailor, a professor of chemistry and biochemistry at the University of California, San Diego and the primary author of a paper describing the results, which is being published in a forthcoming issue of the Proceedings of the National Academy of Sciences.

The researchers designed one type of responder particle with strings of iron oxide, which they called “nanoworms,” that show up brightly in a medical magnetic resonance imaging, or MRI, system. The second type is a hollow nanoparticle loaded with the anti-cancer drug doxorubicin. With the drug-loaded responder, the scientists demonstrated in their experiments that a tumor growing in a mouse can be arrested and then shrunk. “The nanoworms would be useful to help the medical team identify the size and shape of a tumor in a patient before surgery, while the hollow nanoparticles might be used to kill the tumor without the need for surgery,” said Sailor.

[Source: University of California San Diego]

This research is the first time a combination of nanoparticles has been used (successfully) in test animals. Like much of nanomedicine, the application of this approach in human cases is a way off (possibly years).

Yuan Yao, an assistant professor of food science, has successfully modified the phytoglycogen nanoparticle, a starchlike substance that makes up nearly 30 percent of the dry mass of some sweet corn. The modification allows the nanoparticle to attach to oils and emulsify them while also acting as a barrier to oxidation, which causes food to become rancid. His findings were published in the early online version of the Journal of Agricultural and Food Chemistry.

Yao was able to modify the surface of phytoglycogen nanoparticle to make it behave like an emulsifier, creating phytoglycogen octenyl succinate, or PG-OS. PG-OS is thicker and denser than commonly used emulsifiers, creating a better defense from oxygen, free radical and metal ions, which cause lipid oxidation.

Yao’s findings also showed that ?-polylysine, a food-grade polypeptide, can be added to the oil droplets to aid in the protection from oxidation. Polylysine is much smaller than the PG-OS nanoparticles, allowing it to fill in the gaps between PG-OS nanoparticles.

According to Yao’s study, PG-OS nanoparticles with ?-polylysine significantly increased the amount of time it took for oxidation to ruin the oil droplets, in some cases doubling the shelf life of the model product. Shelf life was tested by warming the emulsifiers and checking for chemical reactions that signal oxidation has occurred.

[Source: Purdue University]

A patent is already pending for this use of corn-derived nanoparticles, which is an indicator of how viable the approach may be in terms of commercial application. It seems that the ability of nanoscale materials to make novel and useful surfaces (coatings) is one of the most lucrative and therefore powerful drivers in nanotechnology research.

Using aluminum for fuel is not completely new–the space shuttle’s solid rocket boosters use a small amount of the metal, as will NASA’s Ares rocket. But the new work involves making aluminum one of the key ingredients by using nanoscale particles. These tiny particles, when ignited, combust more rapidly than larger particles, forcing more exhaust gases out of the metal and giving the rocket the necessary kick.

The oxygen and hydrogen in water molecules enhance the combustion of the aluminum. Freezing the propellant keeps it intact, avoiding any premature reactions.

The propellant was able to lift a rocket 396 meters during an August flight test, which was funded by NASA and the Air Force Office of Scientific Research. Now, for even better performance, the researchers are working on adjusting the ratios of different ingredients and possibly mixing the nano-aluminum with larger aluminum particles.

[Source: Technology Review]

For human space flight, the availability of water is obviously important. Being able to refuel in space – without requiring a complex refinery process – may be even more important. That’s why the availability of sufficient water to be a source of fuel may be one of the decisive factors in planning for travel within our solar system. [See SciTechStory: On the Moon or Elsewhere: Follow the Water].

Duke University researchers have demonstrated in animal models that a new nanoformulation can eliminate tumors after a single treatment. After delivering the drug to the tumor, the delivery vehicle breaks down into harmless byproducts, markedly decreasing the toxicity for the recipient.
…
“When used to deliver anti-cancer medications in our models, the new formulation has a four-fold higher maximum tolerated dose than the same drug by itself, and it induced nearly complete tumor regression after one injection,” says Ashutosh Chilkoti, Theo Pilkington Professor of Biomedical Engineering at Duke’s Pratt School of Engineering. “The free drug had only a modest effect in shrinking tumors or in prolonging animal survival”.

As often happens with this kind of research, it is the method of creating the drug or delivery mechanism that provides the most interesting news:

The delivery system makes use of the bacterium Escherichia coli (E. coli) which has been genetically altered to produce a specific artificial polypeptide known as a chimeric polypeptide. Since E. coli are commonly used to produce proteins, it makes for a simple and reliable production plant for these specific polypeptides with high yield.

When attached to one of these chimeric polypeptides, the drug takes on characteristics that the drug alone does not possess. Most drugs do not dissolve in water, which limits their ability to be taken in by cells. But being attached to a nanoparticle makes the drug soluble.

“When these two elements are combined in a container, they spontaneously self-assemble into a water-soluble nanoparticle,” Chilkoti says. “They also self-assemble consistently and reliably in a size of 50 nanometers or so that makes them ideal for cancer therapy. Since many chemotherapeutic drugs are insoluble, we believe that this new approach could work for them as well.”

[Source: Futurity]

If the promise of nanotechnology is to be fulfilled, nanoparticles will have to be able to make something of themselves. An important advance towards this goal has been achieved by researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) who have found a simple and yet powerfully robust way to induce nanoparticles to assemble themselves into complex arrays.
…
“We’ve demonstrated a simple yet versatile approach to precisely controlling the spatial distribution of readily available nanoparticles over multiple length scales, ranging from the nano to the macro,” says Ting Xu, a polymer scientist who led this project and who holds joint appointments with Berkeley Lab’s Materials Sciences Division and the University of California, Berkeley’s Departments of Materials Sciences and Engineering, and Chemistry.
…
Nano-sized particles – bits of matter a few billionths of a meter in size, or more than a hundred times smaller than the stuff of today’s microtechnologies – display highly coveted properties not found in macroscopic materials, including optical, electronic, magnetic, etc. The promise of nanotechnololgy is that exploiting these unique properties on a commercial scale could yield such “game-changers” as sustainable, clean and cheap energy, and the creation on demand of new materials with properties tailored to meet specific needs. Realizing this promise starts with nanoparticles being able to organize themselves into complex structures and hierarchical patterns, similar to what nature routinely accomplishes with proteins.
…
For this study, Xu and her colleagues added [PDP or OPAP] small molecules to various blends of nanoparticles, such as cadmium selenide and lead sulfide, mixed in with a commercial block copolymer – polystyrene-block-poly (4-vinyl pyridine). While she and her group worked with light and heat, she says other stimuli, such as pH, could also be used to reposition small molecules and their nanoparticle partners along block copolymer formations. Strategic substitutions of different types of stimulus-responsive small molecules could serve as a mechanism for structural fine-tuning or for incorporating specific functional properties into nanocomposites.

“Bring together the right basic components – nanoparticles, polymers and small molecules – stimulate the mix with a combination of heat, light or some other factors, and these components will assemble into sophisticated structures or patterns,” says Xu. “It is not dissimilar from how nature does it.”

[Source: Berkeley Lab]

There are many other approaches to nano-manufacture – using nanoparticles to make nano-structures. In all cases, the difficult first step is exerting some control. Some researchers are using highly controlled environments (magnetism, light) and controlled nanoparticles compositions; others are looking to natural models. It’s really a continuum of approaches, and it’s not a horse race to see which approach ‘wins.’ In all likelihood, there will be successes of different kinds and with different methods.