Not the OP but in my experience with lab robotics, locomotion and sensing are the primary problems, as broad as that is. Compared to electrical systems, the hum

Not the OP but in my experience with lab robotics, locomotion and sensing are the primary problems, as broad as that is. Compared to electrical systems, the human muscular and nervous system are extremely sensitive, low mass, and low volume. The dexterity needed to do everything from assemble electronics to fold clothing while sensing the subtleties of cotton versus synthetic threads is simply not possible with electronics while fitting in a reasonable size. For example, just the motors, rotary encoders, and joints of a 6 degree of freedom robotic arm capable of lifting 20 kg (with a specialized tool, no hands or jointed fingers!) are 2-3 times the size of the average human arm without any of the sensing capabilities or dexterity. Beating a single human hand in pipetting at speed, for simple vertical movements, takes up even more space with the xyz ballscrews. Obviously biological systems are much more limited in repeatability, endurance, compliance and so on, but those are the trade offs we get with technology. Maybe on day we'll get artificial muscles and skin but that is all a long ways off and it might only ever be available to super rich.