With gel-filled fingertips, the prosthetic hands have got greater sensitivity; so much so, that now the bionic hands can react "instinctively" to objects slipping from their grasp.
Human hands have an inherent mechanism to estimate the minimum force needed to hold on to an object-by using a built-in reflex that responds to tiny vibrations in the skin as an object starts to slip through our fingers.
However, the reflex mechanism is missing in existing artificial hands, thus operators have to consciously estimate the required force.
"It's very mentally taxing," New Scientist quoted Jeremy Fishel, a member of the research team, as saying.
The researchers have developed a system in which the finger tips consist of a rubber skin, filled with thick silicon gel.
If an object begins to slip, the vibrations in the finger's elastic skin transmit through the silicon gel to sensors attached to a central acrylic "bone".
The vibration provides instant feedback, telling the motors in the hand to tighten their grip before the vibrations stop.
The bone of the finger is also covered with tiny electrodes, across which a small voltage is applied.
The deformations in the elastic skin caused by holding an object alter the distribution of gel in the fingertip, which changes the amount of electricity that is conducted between the electrodes.
The information could then be transmitted to a pressure device worn on a patch of the hand-operator's healthy skin, helping them to "feel" what their prosthetic hand is touching.
A prototype of the finger will be presented at the BioRob conference in Scottsdale, Arizona.