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Silk-Based Optical LensesFrom: Dog
Subject: General
Date/Time 2008-08-20 17:44:57
Remote IP: 66.57.43.56
Messagenote: China at one time(really the world)focused on finding new things they could produce out of Silk and hemp. Then came along petrolium, and well the rest is history.
Silk-Based Optical Lenses Green Enough to Eat
Eric Bland, Discovery News
Aug. 20, 2008 -- Boiling a sleeping insect alive can make for a new generation of "green" optical devices, according to scientists at Tufts University.
The new silk-based lenses are a nontoxic alternative to glass and plastics and could be equipped with tiny sensors to create a new generation of biodegradable medical devices.
"Anything you can do with traditional plastics you could do with silk," said David Kaplan, one of the co-authors of the study that appeared recently in the journal Biomacromolecules.
"It is as green as you can get -- all water processing, natural proteins, etc."
To make their devices Kaplan and his colleagues boiled the pupae of the Bombyx mori silkworm alive to kill them (standard practice for silk processing) and loosen up the raw silk. They then removed the protein glue that holds the single, unbroken, and up to 3,000-foot-long single strand of silk.
The scientists then took the watery solution of silk and poured it onto a mold and let it air dry, doused it with water, and dried it again. From those films they produced optical lenses between 10 and 100 micrometers that were of roughly equal quality to plastic and glass lenses.
"It's not trivial that you can make very clear lenses and films with silk," said Kaplan. "And second, when we expose them to lasers they behave in an interesting fashion and let us diffract white light with lots of control."
The entire process takes place at normal room temperatures and without the toxic chemical solvents most industrial processes use to create many glass or plastic-based optical devices today.
The researchers say that their silk-based products could be a clean, green replacement for nearly anything made of plastic or glass that would eventually degrade naturally over time when exposed to light.
Still, just because a product can be made of silk doesn't mean it will be. The materials come at a high cost.
Feeding silk worms white mulberry leaves, their favorite food, is more expensive than pumping oil or melting sand, basic ingredients for plastic and glass (at least for now). Silk-based products would likely be limited to biomedical devices that are already relatively expensive or where toxicity and the ability to biodegrade are necessary.
The researchers proposed several uses for their silk-based material besides lenses. A silk-based material could be put in put into perishable food that would indicate if it has been contaminated. The material could also be implanted into the body and offer a person a year's-worth of insulin readings before dissolving harmlessly.
Kaplan notes that silk is already a Food and Drug Administration-approved biomedical material, which should speed up, or possibly eliminate, the lengthy FDA approval process.
Jayant Kumar, a material scientist at the University of Massachusetts, Lowell who was not involved in the Tufts research, thinks that the new silk-based products will still have to go through FDA approval.
"It has tremendous potential for biomedical applications beyond just optics," said Kumar. "This technique could be a great way to grow cells and tissues."
According to Kumar, the cultivated tissue could then be implanted into the body and the silk would eventually break down naturally.
"There are already other fibers that can do this," said Kumar. "But they are not easy to produce and are certainly not green at all."
- Silk-Based Optical Lenses: (247) Dog (847) - (Training Log) - 2008-08-20 5:44 pm
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