I am making a prosthetic hand for a competition. For that i have to solve a task with that hand. The task is to identify 3 shapes(square, cylinder and ball) with out seeing that. The size of the items will be in between 50 to 60mm for the side or as the diameter. As per the rule i cannot use a camera. Is there any sensor to identify all these shapes. The sensor should be firmly attachable to the hand without disturbing the normal activities of the hand.