UCSF bioengineer Shuvo Roy and his team have created the world’s first bionic kidney. The coffee-cup-sized device includes a silicon nanotechnology filter to cleanse the blood, while living kidney cells grown in a bioreactor perform the other functions of a natural kidney. A bioartificial kidney could save kidney patients from being stuck on a dialysis machine for life – or dying while waiting for a rare transplant. But is the promise of such a life-changing device enough to convince investors to bring such a thing to market? We talk through the ethics of artificial organs.