16 May 2011—Coaches admire athletes for showing a lot of heart, and poets praise the organ’s passions, but engineers see the human cardiovascular system otherwise. The heart is a pump in a prime location, brimming with energy for the taking, says mechanical engineer Alois Pfenniger. So together with colleagues at the University of Bern and the Bern University of Applied Sciences, in Switzerland, Pfenniger has tested small turbines designed to fit inside a human artery, like an implantable hydroelectric generator.