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Now, self-healing materials can mimic human skin, healing again and again |
| TheAllINeed.com |
(NC&T/UI) "In the same manner that a cut in the skin triggers blood flow to promote healing, a crack in these new materials will trigger the flow of healing agent to repair the damage," said Nancy Sottos, a Willett Professor of materials science and engineering, and the corresponding author of a paper accepted for publication in the journal Nature Materials, and posted on its Web site.
"The vascular nature of this new supply system means minor damage to the same location can be healed repeatedly," said Sottos, who also is a researcher at the university's Beckman Institute.
In the researchers' original approach, self-healing materials consisted of a microencapsulated healing agent and a catalyst distributed throughout a composite matrix. When the material cracked, microcapsules would rupture and release healing agent. The healing agent then reacted with the embedded catalyst to repair the damage.
"With repeated damage in the same location, however, the supply of healing agent would become exhausted," said Scott White, a Willett Professor of aerospace engineering and a researcher at the Beckman Institute. "In our new circulation-based approach, there is a continuous supply of healing agent, so the material could heal itself indefinitely."
To create their self-healing materials, the researchers begin by building a scaffold using a robotic deposition process called direct-write assembly. The process employs a concentrated polymeric ink, dispensed as a continuous filament, to fabricate a three-dimensional structure, layer by layer.
 | | The next generation of self-healing materials, invented by researchers at the University of Illinois, mimics human skin by healing itself time after time. (Photo: L. Brian Stauffer) |
Once the scaffold has been produced, it is surrounded with an epoxy resin. After curing, the resin is heated and the ink – which liquefies – is extracted, leaving behind a substrate with a network of interlocking microchannels.
In the final steps, the researchers deposit a brittle epoxy coating on top of the substrate, and fill the network with a liquid healing agent.
In the researchers' tests, the coating and substrate are bent until a crack forms in the coating. The crack propagates through the coating until it encounters one of the fluid-filled "capillaries" at the interface of the coating and substrate. Healing agent moves from the capillary into the crack, where it interacts with catalyst particles. If the crack reopens under additional stress, the healing cycle is repeated.
"Ultimately, the ability to achieve further healing events is controlled by the availability of active catalyst," said Kathleen S. Toohey, a U. of I. graduate student and lead author of the paper. "While we can pump more healing agent into the network, 'scar tissue' builds up in the coating and prevents the healing agent from reaching the catalyst."
In the current system, the healing process stops after seven healing cycles. This limitation might be overcome by implementing a new microvascular design based on dual networks, the researchers suggest. The improved design would allow new healing chemistries – such as two-part epoxies – to be exploited, which could ultimately lead to unlimited healing capability.
"Currently, the material can heal cracks in the epoxy coating – analogous to small cuts in skin," Sottos said. "The next step is to extend the design to where the network can heal 'lacerations' that extend into the material's substrate."
With Sottos, Toohey and White, the paper's other co-authors are Jennifer Lewis, the Thurnauer Professor of Materials Science and Engineering and interim director of the Frederick Seitz Materials Research Laboratory, and Jeffrey Moore, a William H. and Janet Lycan Professor of Chemistry and a researcher at the Frederick Seitz Materials Research Laboratory and Beckman Institute. White, Sottos and Moore co-invented self-healing plastic; Lewis and White pioneered direct ink writing of three-dimensional microvascular networks.
The work was funded by the U.S. Air Force Office of Scientific Research and the Beckman Institute.
How to make your home heating and cooling system cost effective? By: Ophelia Smith
Did your heating bill again knock your socks off? Why not mine? I have a 2100 plus square foot house but my heating system costs only $200 per month. As compared to me, your bill may be even more than $500. Why is there such a big difference? Let's know the basics to minimize this intolerable difference.
When it comes to my house, its visage is southern and obtains a good heat in winter seasons which turns into shade in summer. Most importantly, it is earth sheltered and on ground floor it is heated by propane heater. Additionally I have a wood stove for wintry days and even it is used for cooking whenever power is off. Higher altitude of mountainous location gives my home an appreciable air conditioning for free.
Now let's look on possible problems in your house. First of all your house may be in city where it gets little sun heat. Even though your house might be new and expensive but still I think insulation may be poor. Additionally you may have conventional gas heating and electric cooling system, both of which are expensive. In this way your house is sucking some extra money from your pocket. Obviously most of the houses in US are power controlled. So what you should do to save money? Here are three valuable strategies to do it efficiently.
1. Make sure to use less gas and power in extra efficient systems like air conditioners, hot water heaters and thermostats.
2. Insulation makes a big difference. You should try to increase insulation in structures which are not properly insulated. Cover all cabinets and shelves in the wall with doors. Also build a porch to shade the windows which will serve to save your home from hot sun. Investment in new sheet rock and insulation is required only once but your bill will come every month. Surely these are old ideas but we need to bring these ideas back to save some useful money.
3. While building your house you should ensure good science. Many builders avoid learning and doing something new so they use conventional ideas which are surely sucking our resources. Also poor quality systems are embedded in these extra large and too fragile houses. For this you need to learn all the basics so you become able to ask your builder for a higher quality.
Always remember houses built on small footprints have proved more energy efficient. Experiences have proved that smaller houses are cheaper to have proper heating and cooling system. Another way of proper heating and cooling is to stack the floors over each other. This way they work more efficiently and save some extra money. Similarly, earth sheltering is another useful approach. By this approach the under ground temperature remains 55 degree and it requires only a small amount of heating and dehumidifying. However some of these structures my not need any cooling or heating but still best thing about them is storm and fire resistance capability. Another option can be the addition of solar collectors to your yard and house. The idea of fireplace can be excellent in cold climates to have good heating environment in your house.
Does all this sounds good for you? Surely, if we go for good science rather than fashion, valuable money can be saved to invest some where else!
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| Quotes | Heres tae the fool on the hill and his pals that are down in the valley.- Wolfstone, Glass and the Can
He thought the formula for water was H-I-J-K-L-M-N-O (H-to-O).
He uses statistics as a drunken man uses lampposts — for support rather than illumination. — Andrew Lang.
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