If you want to make artificial skin that works like the real
thing (a la Lieutenant Commander Data in "Star Trek") then it's
necessary to put together two things: high electrical conductivity that duplicates nerve endings and the
ability to self-repair like a skin wound.
The problem is that although metal provides the
kind of conductivity necessary to duplicate nerves, it doesn't repair well. And softer materials, like plastic-based ones, can self-repair but don't conduct electricity well.
At Stamford, a research team led by Chemical
Engineering Professor Zhenan Bao has found a way to bring those two properties
together. The polymer might one day be used to cover prosthetics, or
even as a new kind of flexible touch screen — one that heals itself. Dropping
the smart phone might become a bit less nerve-wracking.
The work builds on experiments conducted last year, in which Bao's
team used carbon nanotubes to build a flexible
skin-like sensor that could
sense pressure. Now the team has found a way to combine the carbon nanotubes with metal atoms. The group worked with a polymer material that had a specific molecular structure — one where molecules were connected by hydrogen bonds. Hydrogen bonds are relatively weak so they come
apart with little force. But unlike other kinds of bonds they can reconnect resulting in a molecular structure that's the same as it was before. This ability to reconnect after damage was an important component of the self-healing material.
The next component was the ability to conduct electricity. For that, the
scientists added nanometer-sized bits of nickel to the material. The nickel boosted
the material's electrical conductivity, and the more nickel that was added, the
stronger the material became.
In the end, the material Bao and his team developed worked even better than skin: when it
was cut with a scalpel it would repair itself in less than a minute; after a
half hour, it was back at 100 percent of its strength and electrical
conductivity. Skin takes days to do that.
The new material could work as a sensor because when it's
twisted or stretched, the electrical resistance changed. That information could
be transmitted to a computer or eventually to a brain, though there isn't yet
a reliable brain-computer interface.
The one trade-of was the amount of nickel and the electrical
conductivity: an increase in nickel decreased the efficiency of the self-healing. Future work
will be geared to finding the optimal amount.
Credit: Linda A. Cicero, Stanford News Service