I've just started at lexapro dosage for seniors Walker says the robot has about 60 to 70 percent of the function of a human. It stands six-and-a-half feet tall and can step, sit and stand with the help of a Rex walking machine that's used by people who've lost the ability to walk due to a spinal injury. It also has a functioning heart that, using an electronic pump, beats and circulates artificial blood, which carries oxygen just like human blood. An artificial, implantable kidney, meanwhile, replaces the function of a modern-day dialysis unit.