Invented by Swiss watchmakers, the Geneva drive is a two-geared mechanism that produces precise ticks forward. Biomedical engineers at Columbia University have now developed their own tiny Geneva drive - a battery-free “biobot” that can be controlled from outside the body to deliver a drug dosage on command. The squishy Geneva drive clicks forward when an external magnet moves a simple gear, which is just a rubbery piece with embedded iron nanoparticles (the black curved piece in the video). With each click, one of six chambers lines up with a hole and a dose of medicine flows out. A magnet (the silver disk) keeps the device running continuously to demonstrate the mechanism. In clinical use, a doctor could apply a magnet only when a dose is required.