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Flexible Power for Prosthetics

Providing power for prosthetic devices has always been somewhat of a tricky endeavour, frought with compromises. Battery packs are heavy, cumbersome and heat up quite significantly. They have to be carefully placed, to avoid upsetting balance, and the weight offset by stripping out material elsewhere.

If power is required in the section that connects directly to the flesh of the body, the situation is even worse, as batteries do run out and require replacing. This can often mean surgery solely to replace a power source.

As such, finding methods of generating power that use the body itself as a power source much as natural body-parts do, has always been something of a priority. The problem is, how do you do it? What aspects of the body can we safely leech off of? It needs to be something easily renewable. Blood sugar is the obvious choice, but there you run the risk of stripping too much and depriving the body of balance.

Another avenue is piezoelectric power generation, which works off of the body's movement. Piezoelectric materials generate a small electric charge when they are put under stress. Both tension and compression stress alter the structure of the material, producing micro-volts of charge that can be siphoned off to power equipment. By creating multiple separate ribbons of a piezoelectric material with desirable properties, something of a bank charge battery can be produced, where each ribbon generates an independent voltage, which then stack.

Researchers at Princeton University have created a new composite piezoelectric material which has desirable properties for steady electrical flow under stress; producing electrical current within tight parameters. This material is composed of ceramic nanoribbons embedded onto silicone rubber sheets, and creates a situation in which not only is charge generated, but the highly flexible sheets can be placed amid living organic tissue with no threat to their surroundings, and minimal immune response.

Whilst the charge generated is too small to power a prosthetic limb as things currently stand, sheets placed in areas of constant movement - such as in front of the lungs - have been shown to generate enough power to keep a pacemaker running indefinitely. Similarly, such sheets would provide the power needed for other torso-prosthetics, where locomotion is not the primary function.

Still, all hope for prosthetic limbs is not lost either. The researchers have made suggestions of infilling the impact areas of prosthetic feet with the material, taking advantage of the impact with the ground from each step, to power or supplement motors. Shoes worn by organic feet with the same sheets embedded in the soul, could potentially produce enough power to run body area network devices based on walking movement.


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