26 September, 2007

Rocket propelled bionic arm

When you are forced to use a prosthetic device, it usually is quite cumbersome and has disadvantages. But, with this is going to change with the help of rockets.

A diagram of the rocket-powered arm
A diagram of the rocket-powered arm

The new prototype rocket-powered mechanical arm can lift about 9 to 12 kilograms – three to four times more than current commercial prosthetic arms – and can do so three to four times faster.

Researcher Michael Goldfarb, a roboticist at Vanderbilt University in Nashville designed the rocket-powered mechanical arm. It does not have the superhuman strength or capability, but it is closer in terms of function and power to a human arm than any previous prosthetic device that is self-powered and weighs about the same as a natural arm.

The rocket-powered arm also has greater dexterity and freedom of movement than any other prosthetic to date. Conventional prosthetic arms have only two joints, at the elbow and the hand. This prototype though functions more naturally than previous models, with a wrist that can twist and bend, and fingers that open and close independently.
Additional, conventional bionic arms are driven by batteries and electric motors, which has been adequate for the current generation of prosthetic arms because their functionality is so limited that people don’t use them much. But, the more functional the prosthesis, the more the person will use it and the more energy will be consumed. Besides power, also the weight of the batteries needed to power a bionic arm for a reasonable amount of time led to problems.
Goldfarb and his colleagues had to look for alternatives – in this case, rockets. The radical design is similar to rocket systems that help the space shuttle and satellites maneuver in orbit. It employs a miniature rocket about the size of a pencil. It burns pressurized liquid hydrogen peroxide using iridium-coated alumina granules as catalysts, generating pure steam that forces pistons up and down, generating motion. Steam gets vented out through a porous skin-like cover, where it evaporates like normal sweat. Ironically the amount of water involved is about the same as a person would normally sweat from their arm on a warm day.

The steam produced can get up to 232° Celsius, which could potentially hurt either the owner and those in close proximity of the arm. The hottest parts are therefore covered with special insulating plastic, making them safe to touch. A small sealed canister of hydrogen peroxide that fits easily in the upper arm can provide enough energy to power the device for 18 hours of normal activity.

In the end, the robotic arm will be attached to the brain, resulting in natural movements, aroused the same brain. Although, there are robotic arms attached to the brain, it will still be a long time before we can act like it is our own arm. This research though, will cause a big step ahead.

The researchers got their latest prototype working properly at the end of June of 2007. Future research can make the 4-pound arm even lighter and more robust.
Goldfarb also has a parallel project on an artificial leg of similar design, funded by the National Institutes of Health.

Humans, Neuroscience, Robotics