A woman with a hand amputation wore the prosthetic for several hours, which enabled her to pick objects upHao Yang/University of Science and Technology of ChinaA lightweight prosthetic hand that can move almost as freely as a human hand can help wearers carry out intricate tasks, such as tying knots, combing hair and playing chess.To replicate the dexterity of a human hand, most commercial prosthetics use electric motors or compressed air systems, which can make the system heavy and uncomfortable to wear for too long.