Nanotechnology is beginning to open doors for people with artificial limbs. Objects at the nanometer scale are too small for even high-powered microscopes to see, there are 25.4 mln nanometers in one inch. A human hair is about 100,000 nanometers thick. In the early studies of nanotechnology, researchers learned they could reconfigure carbon into a new, ultra-strong and lightweight fiber they named "nanotubes". The challenge research teams face in the development of artificial limbs for humans is to be able to get the data from the sensors to the wearer's brain so that it can directly respond to the stimulation just as if the body part were real.
Collaborative efforts between Oak Ridge National Laboratory, NASA and the National Institute of Aerospace, as well as additional research funded by the U.S. Department of Defense, have developed pressure-sensititive, temperature-sensitive, water-resistant materials made with nanotubes for aeronautic, aerospace, and robotic applications. The materials, embedded with sand, arrays of nanotubes and thin gold wire, have nearly the same heat-conducting ability of human skin and are piezoelectric, generating electricity in response to pressure. While artificial hands have become increasingly life-like in motion and flexibility, most artificial skin is still an unfeeling plastic coating.
The material can be designed to behave as both a temperature and pressure sensor, as a flexible electrical conductor or as part of a polymer material with mechanical and thermal properties similar to those of human skin. The carbon in nano tubes is biocompatible, meaning the body's immune system does not recognize it as a foreign object. In the future this will help to create sensors wired to a person's nervous system allowing information to flow back and forth to the brain. Sensors under the skin are able to measure the electric output or temperature changes and send the data to a computer chip to be interpreted into useful information. The team is currently working on a patch of skin with a surface that resists water and can sense changes in temperature and pressure. The water-resistant top layer will be made from a specially designed nano-structured material. It starts with tiny particles of sand, each one textured to amplify the effect of surface tension, naturally repelling water. Such particles could be sprinkled like powder onto polymers and then bonded to the surface with heat. The coating would keep water or sweat out of seams and joints, where moisture could compromise electronics
Human skin can send message about location of sensations that are 2 millimeters apart. Current artificial skin technology allows detection of pinpricks that are 5 millimeters apart. Researchers are working with nanotechnology to reduce the space between sensor points so that more accurate locations can be identified. When these technologies are successfully debugged and applied, artificial limbs will have the same sensitivity as real skin.

Currently, prostheses are manipulated through a cooperative effort between muscles and mechanics. In an artificial hand, for instance, the user tenses the shoulder or remaining arm muscles that are attached to sensors; these sensors, in turn, send an electronic signal to the mechanics of the artificial hand, telling it to open or close. Technology is working to smooth this process and make it faster by linking to nerves instead of muscles. Advances in artificial skin that allow for more exact data about temperature and pressure changes are only valuable if the person with the prosthesis is able to process and respond to the information. In attempts to address data transfer issues, medical researchers have experienced success with redirecting the arm nerves of amputees into their chest muscles. They have mapped those redirected nerves in the chest to exact places on the hand or fingers where sensations will be received. This has permitted the creation of an electronic connection between the prostheses and the brain so that the subject can, for instance, experience pressure and have the brain send a signal to tell the fingers to withdraw just as the computer would have in a robot. In robots, the sensors lying under the artificial skin report the information they collect through wires connected to a computer, which, in turn, allow the human working with the robot to select the appropriate responses. Developers' hope that by 2010, the data transfer technology--electronic circuits and software to manage the process--will be fast enough to allow the limb user to sense and respond to stimulation just as quickly as he/she would if the limb were natural. Through this program's success, a person who has artificial hands will be able to feel the warmth of a baby's bath water and type on a computer keyboard as readily as anyone else does.

Polyimide, also known as FILMSkin, is being made to look and feel as real as human skin, too. It is lightweight but stretchable, allowing flexibility for movement with the prostheses, and it sheds water just like human skin, which is an important quality in protecting the electronics within. Scientists are currently studying how to use the piezoelectric qualities of the nanotubes to develop ways to power the electronics within the skin by using solar or body heat energy so that batteries are not required.