Tough Stuff…Two New Materials That Will Surprise You (and A Very Old Metal with New Product Potential)!
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| by Shelley Kronzek |
| Nanotechnology and research-borne new nano-materials are revolutionizing the strength, size, and durability of what were long considered benign materials and elements. A prime example of a forgettable material becoming important is the graphite within a pencil (commonly called lead). Graphite is a carbon allotrope, an electrical conductor, and a semi-metal. Allotropes are structurally different forms of the same element, in which the same atoms bond together in different ways. Graphite, a soft material, is now the main component of graphene, one of the strongest materials in existence. Hydrogels, developed from water, are extremely stretchy, tough and invaluable for developing materials to replace damaged cartilage in human joints! |
| I. Graphene is a term that was first coined by Hanns-Peter Boehm and is a single-atom layer of pure carbon. It is an atomic-scale honeycomb lattice made of carbon atoms that has the appearance of chicken wire. |
Wikipedia |
| Graphene is the basic structural element within graphite, charcoal, carbon nanotubes, and fullerenes. Graphene is extremely strong, an excellent conductor, and with no internal structure at all, it offers an abundance of surface area — much like a sheet of paper. Researchers have worked hard developing new products with graphene and have aspirations of graphene replacing silicon as the main element for computer chips as well as using graphene instead of lithium for batteries. |
| The Nobel Prize in Physics for 2010 was awarded to Andre Geim and Konstantin Novoselov at the University of Manchester "for groundbreaking experiments regarding this two-dimensional material." |
American Society for Microbiology News Site |
| The discovery of graphene is quite significant due to the development of new graphene-based materials that have applications in electronics, energy storage, sensing, and biomedical devices. In 2011 MIT researchers discovered graphene's effectiveness as a photo detector, while at the University of Maryland scientists using bi-layer graphene (two atoms thick instead of one atom thick) developed a temperature-sensitive device more than 1,000 times faster than existing technologies. It's capable of recognizing a very broad range of light energies, which means it could be very useful in everything from biochemical weapons detection to airport body scanners. While this sounds promising, the new graphene photodetector has a high electrical resistance, and it will require tweaks to absorb enough light to be useful. That means years of research and development before we see commercial products. |
| In March 2012, The Graphene Research Group at Toyohashi University of Technology successfully synthesized graphene by reducing graphene oxide using microorganisms extracted from a local river. This approach offers a low-cost, highly efficient method for the mass production of high-quality graphene for the electronics industry and more. At Rice University (where the pivotal work in Carbon Nanotubes was first done by Dr. Richard Smalley) researchers report that electric current shoots straight across a sheet of defect-free graphene with almost no resistance, a feature that makes the material highly attractive to engineers who would use it in products such as touchscreens and other electronics, according to Rice theoretical physicist Boris Yakobson. He is co-author of a new paper about graphene formation that appeared last week in the Proceedings of the National Academy of Sciences. Graphene is also considered to be the world's thinnest known coating for protecting metals against corrosion. This list goes on and will undoubtedly grow within the coming years. |
| September 2012 reports reveal that researchers at the Norwegian University of Science and Technology have successfully been growing and now have patented GaAs nanowires on graphene for commercial purposes. Such products made of semiconductors grown on graphene are expected to become the basis for new types of device systems, and could fundamentally change the semiconductor industry. According to Professor Helge Weman of Norwegian University of Science and Technology: |
| "Graphene is experiencing tremendous attention worldwide. Companies like IBM and Samsung are driving this development in the search for a replacement for silicon in electronics as well as for new applications, such as flexible touchscreens for mobile phones. Well, they need not wait any more. Our invention fits perfectly with the production machinery they already have. We make it easy for them to upgrade consumer electronics to a level where design has no limits." |
| What I find to be the most promising use of graphene is that research shows that graphene-based materials can kill bacteria in two ways. Researchers at the Norwegian University of Science and Technology have found that graphene derivatives, like graphene oxide and reduced graphene oxide, inhibit the growth of E. coli bacteria. Graphene is biocompatible (particularly graphene oxide) and cells can grow very well on graphene substrates. Graphene may be used to make antibacterial paper, according to new work by researchers at the Chinese Academy of Sciences in Shanghai. The list of benefits and new products keeps growing. Keep an eye out and ear listening for new developments within technology and biotechnology for this relatively new nanomaterial! |
| II. Hydrogel is a network of polymer chains that are water insoluble. Hydrogels contain over 99 percent water and are superabsorbent polymers. Hydrogels also possess a degree of flexibility very similar to natural tissue due to their significant water content. |
| Hydrogels were first announced and celebrated in 2007, but 2012 has been a year for new developments in this health-related area. The online Early Edition of the Proceedings of the National Academy of Sciences reported on March 5, 2012, that University of California, San Diego, bioengineers had developed a self-healing hydrogel that binds in seconds, as easily as Velcro, and forms a bond strong enough to withstand repeated stretching. The material has numerous potential applications, including medical sutures, targeted drug delivery, industrial sealants, and self-healing plastics. |
| More recently, a team of experts in mechanics, materials science, and tissue engineering at Harvard has created a "Hydrogel" as its main ingredient is water. This new gel can stretch to 21 times its normal length and is exceptionally tough, self-healing, and biocompatible — a valuable collection of attributes that opens up new opportunities in medicine and tissue engineering. The material, its properties, and a simple method of synthesis are described in the September 6 issue of Nature. |
| Jeong-Yun Sun is a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences (SEAS). Sun and his coauthors were led by three faculty members: Zhigang Suo, Allen E. and Marilyn M. Puckett Professor of Mechanics and Materials at SEAS and a Kavli Scholar at the Kavli Institute for Bionano Science and Technology at Harvard; Joost J. Vlassak, Gordon McKay Professor of Materials Engineering and an Area Dean at SEAS; and David J. Mooney, Robert P. Pinkas Family Professor of Bioengineering at SEAS and a Core Faculty Member at the Wyss Institute for Biologically Inspired Engineering at Harvard. |
| The group's combined expertise in mechanics, materials science, and bioengineering enabled the group to apply two concepts from mechanics — crack bridging and energy dissipation — to a new problem. |
| To create the tough new hydrogel, the Harvard researchers combined two common polymers. The primary component is polyacrylamide, known for its use in soft contact lenses and as the electrophoresis gel that separates DNA fragments in biology labs; the second component is alginate, a seaweed extract that is frequently used to thicken food. Separately, these gels are both quite weak — alginate, for instance, can stretch to only 1.2 times its length before it breaks. Combined in an 8:1 ratio, however, the two polymers form a complex network of crosslinked chains that reinforce one another. The chemical structure of this network allows the molecules to pull apart very slightly over a large area instead of allowing the gel to crack. |
| The new hydrogel is capable of maintaining its elasticity and toughness over multiple stretches. Provided the gel has some time to relax between stretches, the ionic bonds between the alginate and the calcium can "re-zip," and the researchers have shown that this process can be accelerated by raising the ambient temperature. |
| Beyond artificial cartilage, the researchers suggest that the new hydrogel could be used in soft robotics, optics, artificial muscle, as a tough protective covering for wounds, or "any other place where we need hydrogels of high stretchability and high toughness." |
| III. Copper and Its Antibacterial Qualities. If you think that graphene is an interesting nanomaterial, let's end our "tough stuff" article by discussing a regular metal, the element copper (Cu), for a moment. Copper has been in use for at least 10,000 years, but more than 95 percent of all copper ever mined and smelted has been extracted since 1900. |
| Recycling is a major source of copper today throughout the world. Copper is 100 percent recyclable without any loss of quality. |
| Copper is a very soft metal. Copper ions are water soluble, where they can function at low concentration as bacteriostatic substances, fungicides, and wood preservatives. Copper alloys can kill bacteria, fungi, and viruses. The metals can be manufactured into everything from IV poles to sinks to bed rails — just about anything that is frequently touched in hospitals. While disease-causing organisms can exist on stainless steel surfaces for two weeks (what most hospital beds, sinks, and bed rails are made of), according to a recent University of Arizona research study, 99.9 percent of disease-causing organisms die within two hours on surfaces that contain at least 60 percent copper! |
| According to the Reuters Health report on July 1, 2011, based upon a study for the World Health Organization's Prevention and Infection Control Conference in 2011, hospital-acquired infections are the fourth leading cause of death in the United States, killing more people than AIDS and breast cancer combined. That's 2 million infections annually, and 100,000 deaths — one infection for every 20 people admitted to hospitals. |
| Metallic copper surfaces kill microbes on contact, decimating their populations, according to a paper in the February 2011 issue of the journal Applied and Environmental Microbiology. They do so literally in minutes, by causing massive membrane damage after about a minute's exposure, says the study's author, Gregor Grass of the University of Nebraska, Lincoln. Grass and his research team have been working with the Ronald MacDonald Foundation in testing medical equipment surfaces made from copper instead of stainless steel. Early results are VERY promising. The real test will be to see if antibacterial copper coating proves effective or not in controlling hospital-borne infections and hopefully its use will result in measurable decreases in infections. |
| While copper combined with magnets have been sold for decades and are advertised as having medicinal qualities, too much copper within the body (say through drinking water) can have disastrous results on the liver and kidneys. |
| Graphene, hydrogels, and copper are but a few materials that are in the news this year. Universities, hospitals, and tech and biotech companies worldwide are experimenting with nanomaterials, elements, and alloys of all kinds. R&D budgets are heavily skewed towards nanomaterial development and biotech research. The effectiveness and lifespan of medical, technological, and communications products, services, and procedures will increase dramatically as the elements and materials currently being tested in laboratories make it to the consumer level. |
| If you like this article, you might appreciate two Dover classic works: |
| Introduction to Superconductivity: Second Edition, by Michael Tinkham |
| Solid State Theory, by Walter A. Harrison |
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| References: |
1. Harvard School of Engineering and Applied Sciences news release September 5th 2012:
http://www.seas.harvard.edu/news-events/press-releases/tough-gel-stretches-to-21-times-its-lengthy |
| 2. Nanotech News: http://phys.org/nanotech-news/nano-materials/ |
| 3. Physics.org, All About Graphene: http://www.physics.org/article-questions.asp?id=67 |
4. American Society for Microbiology News Site:
http://archive.asm.org/index.php/news-room/dry-copper-kills-bacteria-on-contact.html?title=Dry+Copper+Kills+Bacteria+on+Contact |
| 5. Oxford Journals & Reuters News: http://cid.oxfordjournals.org/content/53/7/i.full |
| 6. Various mini-news releases in Science Daily on Hydrogels, Graphene, Copper |
7. Graphene
pics a. Wikipedia: http://en.wikipedia.org/wiki/Graphene
b. Mobile Local Social.com: http://mobilelocalsocial.com/2010/graphene-cpu-from-intel-reaches-100ghz/ |
