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Contact lenses with circuits, lights a possible platform for superhuman vision

Contact lenses with metal connectors for electronic circuits were safely worn by rabbits in lab tests. Credit: University of Washington

 Movie characters from the Terminator, the Bionic Woman to Star Trek use bionic eyes to zoom in on far-off scenes, have useful facts pop into their field of view, or create virtual crosshairs. Off the screen, virtual displays have been proposed for more practical purposes – visual aids to help vision-impaired people, holographic driving control panels and even as a way to surf the Web on the go.

 The device to make this happen may be familiar. Engineers at the University of Washington have for the first time used manufacturing techniques at microscopic scales to combine a flexible, biologically safe contact lens with an imprinted electronic circuit and lights.

 Looking through a completed lens, you would see what the display is generating superimposed on the world outside," said Babak Parviz, a UW assistant professor of electrical engineering. "This is a very small step toward that goal, but I think it's extremely promising." The results were presented today at the Institute of Electrical and Electronics Engineers' international conference on Micro Electro Mechanical Systems by Harvey Ho, a former graduate student of Parviz's now working at Sandia National Laboratories in Livermore, Calif. Other co-authors are Ehsan Saeedi and Samuel Kim in the UW's electrical engineering department and Tueng Shen in the UW Medical Center's ophthalmology department.

There are many possible uses for virtual displays. Drivers or pilots could see a vehicle's speed projected onto the windshield. Video-game companies could use the contact lenses to completely immerse players in a virtual world without restricting their range of motion. And for communications, people on the go could surf the Internet on a midair virtual display screen that only they would be able to see.

A researcher holds one of the completed lenses. Credit: University of Washington

"People may find all sorts of applications for it that we have not thought about. Our goal is to demonstrate the basic technology and make sure it works and that it's safe," said Parviz, who heads a multi-disciplinary UW group that is developing electronics for contact lenses.

The prototype device contains an electric circuit as well as red light-emitting diodes for a display, though it does not yet light up. The lenses were tested on rabbits for up to 20 minutes and the animals showed no adverse effects.

Ideally, installing or removing the bionic eye would be as easy as popping a contact lens in or out, and once installed the wearer would barely know the gadget was there, Parviz said.

Building the lenses was a challenge because materials that are safe for use in the body, such as the flexible organic materials used in contact lenses, are delicate. Manufacturing electrical circuits, however, involves inorganic materials, scorching temperatures and toxic chemicals. Researchers built the circuits from layers of metal only a few nanometers thick, about one thousandth the width of a human hair, and constructed light-emitting diodes one third of a millimeter across. They then sprinkled the grayish powder of electrical components onto a sheet of flexible plastic. The shape of each tiny component dictates which piece it can attach to, a micro-fabrication technique known as self-assembly. Capillary forces – the same type of forces that make water move up a plant's roots, and that cause the edge of a glass of water to curve upward – pull the pieces into position.

The prototype contact lens does not correct the wearer's vision, but the technique could be used on a corrective lens, Parviz said. And all the gadgetry won't obstruct a person's view.

"There is a large area outside of the transparent part of the eye that we can use for placing instrumentation," Parviz said. Future improvements will add wireless communication to and from the lens. The researchers hope to power the whole system using a combination of radio-frequency power and solar cells placed on the lens, Parviz said.

A full-fledged display won't be available for a while, but a version that has a basic display with just a few pixels could be operational "fairly quickly," according to Parviz.

Source: University of Washington

Protein in human hair shows promise for regenerating nerves

A protein found in human hair shows promise for promoting the regeneration of nerve tissue and could lead to a new treatment option when nerves are cut or crushed from trauma.

In the current issue of Biomaterials, scientists from Wake Forest University School of Medicine reported that in animal studies the protein keratin was able to speed up nerve regeneration and improve nerve function compared to current treatment options.

“We found that the nerve repair happened more quickly and consistently, and that functional recovery was higher,” said Mark Van Dyke, Ph.D., senior author and an assistant professor of regenerative medicine. “The fact that we were able to accomplish this with gels made from keratin is pretty remarkable.”

Current treatments for repairing damaged nerves include microsurgery to sew two ends of the nerve together, using a nerve from another part of the body to replace a damaged section, or placing an empty tube between the cut ends so that nerve fibers can grow through it and back into the muscle.

Grafting a nerve from another part of the body is usually the most effective option, but it creates another injury site and isn’t possible in all patients. The tubes, known as nerve guidance conduits, cannot be used in gaps longer than three or four centimeters. In addition, nerve regeneration with this method is not always successful. For example, after about age 17, nerves don’t regenerate as well.

Laboratory scientists have tried placing natural materials, such as collagen, into the conduits to promote nerve regeneration. Van Dyke’s team was the first to use keratin, which is believed to contain molecules that regulate cell behavior.

The scientists collected human hair from a local barber shop and chemically processed it to remove the keratin. They purified the keratin protein and used it to form gels that were then used to fill the nerve guidance conduits. They studied how keratin affects the activity of Schwann cells, which play a vital role in nerve regeneration. These cells produce signals that tell nerve cells to begin regenerating and “remodel” the blood clot that has formed so that nerve cells can grow across it.

“By using keratin to activate these cells, we’re trying to tap into the natural healing cascade,” said Van Dyke. “We believe that keratin helps amp up Schwann cell activity and give the nerve regeneration process a head start.”

The laboratory studies showed that keratin activated Schwann cells and increased their proliferation and migration. Next, the scientists used a keratin-filled tube to attempt to repair a 4 millimeter nerve gap in mice -- a fairly significant gap considering the size of the animal.

The results from these animals were compared with animals treated with an empty nerve guidance conduit and with animals treated with a nerve graft.

After six weeks, 100 percent of the animals in the keratin and nerve graft groups showed visible nerve regeneration across the gap, compared to only 50 percent who got the empty conduit. The speed of repair was best in the keratin group.

The scientists then tested the function of the regenerated nerve. The speed of nerve impulses was best in the keratin group. The amount of signal that got through the nerve was better in the keratin group than in the empty tube group. The study was recently highlighted in the journal Science.

“The results suggest that a conduit filler derived from hair keratins can promote an outcome comparable to a grafted nerve,” said Van Dyke.

In the study, the nerve function did not translate into recovery of muscle function, but the scientists suspect they may have tested too early, before the nerve had time to regenerate to the muscle. It is known that muscle function recovery lags behind nerve recovery. Future studies will focus on regeneration across larger gaps and will test whether nerve regeneration results in a return of muscle function.

Source: Wake Forest University Baptist Medical Center

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