Our bodies naturally run on electricity – we just don't often think of it that way. While real human body parts obviously don't get their electricity from batteries or wall outlets like bionic body parts do, scientists are taking inspiration from this common use of electrical power to create better bionic hands.
Mimicking the way our muscle fibers naturally use electricity to power their contractions, researchers at Saarland University in Germany were able to build a bionic hand that looks, feels and functions more like a biological one. The new system is notably more lightweight than those commonly used today — presenting a potential solution to the common complaint that prosthetics are too heavy.
Each time you move a part of your body, your brain sends an electrical signal down through your spinal cord and out to the appropriate muscle fibers. That electrical signal then powers the contraction, or tightening, of the muscle fibers. When muscle fibers contract, they cause the muscle as a whole to get shorter — which in turn moves the bones attached to the muscle. So if your fingertip is hovering over the "I" key and you want to hit the "K" key next, your brain must send an electrical signal for the muscles on the palm-side of your finger to contract and pull your fingertip down toward that key.
It's an elegant and effective system — one that has long eluded bionic limbs. Previous bionic limbs have been literally weighed down by a much clunkier, less lifelike system that uses electronic sensors to monitor the positions and guide the movements of their parts.
The new system does away with the need for heavy external sensors by incorporating "smart wires" that are able to contract in response to electrical signals, just like natural muscle fibers do. Made from strands of nickel-titanium wire, each metallic muscle fiber is only about the width of a human hair.
When an electrical charge runs through the smart wire, it contracts. Once the electrical charge gets turned off, the wire automatically returns to its original shape. This system requires just one semiconductor chip to control the wire's shape, rather than multiple bulky external sensors.
The bionic hand is still in the prototype phase, but the researchers will to continue to improve their system so that it can one day offer patients in need of prosthetics a more natural option.
