The lighter wand for your gas BBQ,a submarine's sonar device and the ultrasound machine at your doctor's office all rely on piezoelectric materials, which turn mechanical stress into electrical energy, or vice versa. In 1997,researchers developed piezoelectric materials that were 10 times better at coupling electrical and mechanical responses than prior state-of-the-art materials. But even scientists did not understand why the newer materials were so responsive.
Source: phys.org