Around the world, thousands of people who are missing limbs are wearing custom-fitted replacements. In operating theatres, surgeons are using 3D replicas of their patients’ bodies to guide operations.

Kodjo Afate Gnikou, a resourceful inventor from Togo in West Africa, has made a $100 3D printer which he constructed from parts he scrounged from broken scanners, computers, printers and other e-waste ...