Blog @ NanoVic - Nanotechnology Blog

My daughter Clem and I spent some time recently playing with “magic sand”: super-hydrophobic powder from Educational Innovations.  It is a compelling demonstration, but we hadn’t many good ideas about applications.  Just today, though, I saw that Oak Ridge National laboratory in the US have developed a new super-hydrophobic coating, which can be made cheaply (from powdered glass) and applied over large surfaces.

The thing that attracted me was the description of how the nano-structured material “maintains a microscopic layer of air on surfaces even when submerged in water, resulting in a profound change in the basic water-solid interface”. The inventor, John Simpson likes to refer to this as the “Moses effect” – and I love the name!  He also speculates about how such a layer could significantly reduce the drag experienced by a ship moving through water, potentially saving a lot of energy.

There’s more…  Another feature of this powder is its thermal insulation. Water does not enter the grain pores because the powder grains are superhydrophobic. This results in a dry breathable coating with trapped insulating air throughout. And, because the powder consists almost entirely of porous amorphous silica, it also makes a very good electrical insulator. In addition, since the powder creates a layer of air between the coated substrate and any water on the surface, water-based corrosion of the substrate is greatly reduced or entirely eliminated. 

The wikipedia entry on nanobacteria still cautiously starts by defining them as ‘a possible class of living organisms’, but two recently published, independent studies have given increased weight to the hypothesis that they are not living creatures after all.

Image credit: Martel and Young. PNAS.

The nanoscale structures containing calcium and protein were first termed ‘nanobacteria’ by geologist Robert Folk who reported them after seeing nanoparticles on scanning electron micrographs of mineral samples he’d collected from hot springs in Italy.

Ever since they were first reported, there has been controversy as to whether or not they could possibly be ‘alive’, as DNA is around 2nm wide, and some proteins are known to be bigger than the proposed size of the nanobacteria. Studies conflicted, with some reports showing that the nanobacteria could increase in number, implying an ability to reproduce (at a slow rate), yet other studies showed that no DNA could be detected in the nano-sized structures.

The two most recent papers in PLoS and PNAS show that, whilst these structures do exist and have interesting properties, they do not seem to be alive. A group from Taiwan were able to show that the nanostructures could be formed when calcium carbonate solution was incubated in a nutrient solution. A protein in the nutrient solution called albumin, commonly found in serum which is used in routine human cell culture, was found to help seed formation of these particles. No DNA was found in the particles. A team from France also found that the nanostructures of calcium carbonate could form in complex with a protein called Fetuin, and that these particles could seed formation of new particles, in a process likened to that of prions- catalytic proteins that cause mad-cow disease and scrapie but are themselves not ‘alive’.

The nanoparticles of calcium carbonate have been reported to be involved in all sorts of disease states such as arthritis, artherosclerosis and kidney stones, and while these recent studies mean they might not be living organisms, they still may have interesting medical implications. I’ll wait to see what the after-life holds for the ‘nanobacteria’!

I have been reading with interest about a wiperless windshield.  Designed by Italian car designer, Leonardo Fioravanti of Pininfarina the ”Hidra” is a working prototype concept car.  The Hidra has an aerodynamic design and uses four layers to achieve this effect.

The top layer repels water and protects from the sun.  The second layer features “nano-dust” which pushes the dirt to the outer edges of the windshield.  This layer is activated by the third layer which senses the dust in the first place.  The last layer conducts electricity which keeps it all up and running.

Sounds like a great idea - although it mentions it will take around five years before it finds its way to the family car.  Would be good if they could create a completely self cleaning car, especially as here in Melbourne at the moment, we have plenty of dust gathering on our cars due to lack of rain and restrictions on washing them! 

A few weeks ago I was helping my housemate mend her punctured tyre on her bike.  We had to dismantle the wheel, remove the inner tube, figure out where the leak was using sophisticated technology like sticking it in a bucket of water looking for the bubbles and then basically stick a rubber bandaid over the hole.  It wasn’t difficult, but imagine what it would be like if you never had to fix a puncture again.  If the rubber just melded itself back together and off you went.   

It could happen!  In normal rubber compounds the forces that hold the molecules together are covalent cross-links, ionic bonds and hydrogen bonds.   Researchers at ESPCI in Paris have created a rubber like material from fatty acids and urea where molecules are linked only by hydrogen bonds.  This makes the material less strong, but imparts a remarkable ability for the material to repair itself when it is compressed at room temperature.  It can be cut, and it heals itself.  It loses no strength in the process, which can be repeated over and over. 

 So, if I would like a self repairing tyre, what would you make with your self-repairing ‘smart’ rubber?!

Sarah recently posted on the Bridge8 blog about meeting Don Eigler, IBM fellow from IBM Almaden Research Center (USA) at ICONN08. (Pictured are Mrs Francesca Calati of La Trobe University, Don Eigler, Prof Chennupati Jagadish from ARCNN and Assoc Prof Joe Shapter from Flinders University)

So who is Don? You might remember some excitement amongst physicists and molecular scientists in the late 1990s when some IBM guy managed to manipulate individual xenon atoms to spell out the word “I-B-M”.   

That guy was Don Eigler. Don then and now works on extending human understanding of the physics of atomic-scale structures and exploring the potential of atomic-scale logic and data storage technologies. Don is remarkable not only for his capacity to dream big and make things happen for IBM, but also for his willingness to participate in the scientific process at many levels.

In addition to delivering a plenary lecture at ICONN2008, Don inspired a whole new generation of scientists by chatting to teenagers and their supervisors attending the conference student and teacher nanotechnology teaching sessions. He provided simple and yet unpatronising explanations of atoms, electron microscopy and data storage amongst other topics, and willingly answered questions and posed for photos (we are such atomic celebrity junkies!).

A gecko-inspired medical adhesive may have potential applications for sealing wounds and for replacement or augmentation of sutures or staples. 

US researchers have used a polymer poly(glycerol-co-sebacate acrylate) and modified the surface to mimic the nanotopography of gecko feet, which allows attachment to vertical surfaces.  Ideally these adhesives would also have the ability to deliver drugs or growth factors to promote healing.  The findings have been published in Proceedings of the National Academy of Sciences.

As a first demonstration, a gecko-inspired tissue adhesive from a biocompatible and biodegradable elastomer combined with a thin tissue-reactive biocompatible surface coating was been created. Tissue adhesion was optimized by varying dimensions of the nanoscale pillars, including the ratio of tip diameter to pitch and the ratio of tip diameter to base diameter. Coating these nanomolded pillars of biodegradable elastomers with a thin layer of oxidized dextran significantly increased the interfacial adhesion strength on porcine intestine tissue in vitro and in the rat abdominal subfascial in vivo environment.

Perhaps this might also lead to taking the ‘ouch’ out of removing bandaids from the skin!

Despite its beautiful, floating appearance in the narrow walkways of your garden, spider silk is stronger than steel and can be extended 30-50% of its length before it breaks.  Unraveling the secrets behind the strength of spider silk is attracting a lot of research dollars - if we could replicate it synthetically, imagine the impact on fabric technology, tethering equipment and load-bearing materials.  As reported recently in Science Daily, the eternal question of how spider silk manages to be such an amazing natural substance is being tackled by researchers in Civil and Environmental Engineering at Massachusetts Institute of Technology, USA.  The group has recently published some interesting data.  Crazily enough, it apparently all boils down to the basic hydrogen bond.  Along the length of the spider silk, groups of 3-4 hydrogen bonds form nanocomposite structures within the protein assembly, binding together repeated stacks of short protein beta strands.  Overall, hydrogen bonds arranged in such groupings of 3-4 resist force and dissipate energy; any fewer bonds, and the silk is not strong enough. Any more, and there is no net gain in strength. This incredible arrangement of beta sheets and hydrogen bonds is also found in muscle tissue and amyloid fibres, suggesting that increasing protein strength by this method offered a distinct evolutionary advantage (evolution is my favourite topic at the moment). So next time you stumble through a web, and maniacally tear at your web-infested hair in utter panic, just spare a thought for the humble hydrogen bond and evolution. I know I will.

Lovers of carbon nanotubes as I know you all are, it’s time to move over and make way for boron……or so say Jun Ni and his research team in Beijing, China. Boron is the 5th element in the periodic table, having the chemical symbol B (carbon, C, is the 6th element). As would be expected from their divergent periodic groupings, boron nanotubes assemble with a different chemistry to those of carbon. Rather than forming the classic ‘chicken-wire’ pattern, boron atoms are naturally inclined to form a buckled triangular latticework. However, theoretical modelling by Ni and his colleagues has allowed them to predict that adding an extra atom to the centre of some hexagons in the unstable ‘carbon-like’ boron lattice would confer the nanostructure with enough stability to be used commercially. Boron nanotubes of differing diameters are predicted to have a range of possible applications, largely as a result of varied electrical properties; wide tubes should be metallic conductors and perhaps even superconductors at high temperatures. Narrow tubes would offer value in the form of semiconductors. The next step in the boron nanotube story is to find an effective catalyst for production by chemical vapour deposition. Personally, I find all this chemistry talk really exciting….hope none of you found this blog too boron-ing. [Image courtesy of New Scientist]

Courtesy Atsushi Asano, Cornell University

While not quite on the nanoscale, an average human sperm on average is about 0.055 mm long, sperm have provided inspiration for how to power nano-sized devices. Energy to power the sperm tail (flagellum) comes from the mitochondria, the power stations of the cell, while the rear section of the tail or ‘principal piece’ gets it’s energy from glycolysis, the direct breakdown of glucose to produce energy. It’s this process that has inspired researchers at the Cornell NanoScale Science and Technology Facility to try and mimic this process to provide a power source for nanodevices. In sperm, the 10 enzymes required for glycolysis are attached to scaffolding proteins in the sperm tail, holding them in place in a unique conformation. Scientists engineered and tethered 3 of the 10 proteins to a gold surface covered in nickel ions, whilst retaining the enzymes activity. Researchers are now looking to extend the project to include all 10 protens necessary to complete a nano ‘power supply’.

A recent online poll by COSMOS magazine asked people what they thought would be the most likely cause to the end of humanity. In a good sign for nanotechnology, only 4% of people thought that nano “grey goo” would be the catastrophic cause. The term “grey goo” referes to the potential exponential growth of self-replicating nanobots, highlighted in many science fiction stories incorporating nanotechnology such as Michael Crichton’s Prey. The man who coined the term, Eric Drexler, has said that “An obsession with obsolete science-fiction images of swarms of replicating nanobugs has diverted attention from the real issues raised by the coming revolution in molecular nanotechnologies,” said Drexler. “We need to focus on the issues that matter—how to deal with these powerful new capabilities in a competitive world.”

In perhaps not such a great sign for humanity, the leading predicted cause of our eventual downfall was human induced climate change (35%), which for me personally is certainly a much more concerning problem which requires immediate action than the sci-fi version of swarms of marauding nanobots!