Ultrasound, which works on the principle of piezoelectricity, is finding a second lease of life in medicine, Wired outlines. Applying voltage to a piezoelectric crystal makes it vibrate, sending out a sound wave. When the echo that bounces back is converted into electrical signals, you get an image of, say, a fetus, or a submarine. But in the last few years, the lo-fi tech has reinvented itself in some weird new ways. From a report: Researchers are fitting people's heads with ultrasound-emitting helmets to treat tremors and Alzheimer's. They're using it to remotely activate cancer-fighting immune cells. Startups are designing swallowable capsules and ultrasonically vibrating enemas to shoot drugs into the bloodstream. One company is even using the shockwaves to heal wounds -- stuff Curie never could have even imagined. So how did this 100-year-old technology learn some new tricks? With the help of modern-day medical imaging, and lots and lots of bubbles.