Monday, 29 Sep, 2008 Science

Artificial Hands May Soon Feel Objects


Artificial hands filled with gel could show a sensitive touch, being able to demonstrate "instinctive" reaction to objects that slip from their grab.

Human hands use a built-in reflex that reacts to small vibrations in the skin when a specific object slips through fingers. Scientists say that unlike human hands, the bionic hands do not have the reflex mechanism which would help automatically calculate the minimum force that is required to hold on to an object. This is why the operators of the artificial hands have to calculate the required force consciously.

According to Jeremy Fishel of University of Southern California, Los Angeles, this task is mentally quite tough. He is one of the team members that developed a new fingertip.

The scientist mentioned that the tip of an artificial arm is made of a rubber skin, being filled with thick silicon gel. In case an object starts slipping, the vibrations within the elastic skin of the bionic finger pass through the silicon gel to acoustic sensors that are connected to an inner acrylic "bone". The whole mechanism generates a prompt feedback, signaling the motor in the bionic hand to tighten their grip till the moment when the vibrations stop.

The bone of the artificial finger is covered with little electrodes and a small voltage is used in each one of them. When the arm holds an object, its elastic skin deforms thus shifting the allocation of gel in the fingerprint and altering the level of electricity that goes between the electrodes. Such information is sent out to a pressure device that is worn on a patch of the healthy skin of the person who operates the arm. This helps the person to "feel" what their bionic arm is touching.

The prototype of the invention will be presented in October at the BioRob conference, which will be held in Scottsdale, Arizona.

Source: NewScientist

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