Putting a New Spin on Sound Waves

It's already possible to do some really extraordinary things with sound waves, like levitating small particles and manipulating them in-air (useful for caustic chemistry reactions) but we're about to see another tool added to the sonic utility belt: spin. Scientists from Nanjing University in China have recently created a passive device that, for the first time, easily allows planar sound waves to be converted into corkscrew-shaped spiral waves without requiring elaborate geometric arrangement...