A prosthetic arm and hand from researchers at Johns Hopkins University can precisely duplicate every movement of a natural arm. The hand incorporates a small computer and draws on 100 sensors and 17 motors to drive 26 joints, all guided by the wearer's brain signals. "What we have done is, by order of magnitude, increase the ability to do very highly dexterous kinds of motions. So you can think about things like eventually playing the piano ... I think we'll get there someday," said Michael McLoughlin of the university's Applied Physics Laboratory.