“Haptics” is what we’re talking about here – the field which integrates computing and touch. It’s long been the preserve of robots, huge gloves, and virtual reality glasses, but now a team of Japanese researchers have worked out how to use ultrasound for the same purpose.
Here’s the science: sound is a pressure wave and that pressure can be applied to anything. As very low frequency sound waves interfere, they create a focal point that feels like a solid object. Therefore, if you can get that pattern of interference right, then you can make air feel solid.
At the moment, it’s still quite basic. They can only make vertical surfaces, and those aren’t too strong. It’s not wise to make the ultrasound too strong or you risk ear damage. If it goes well, though, the scientists reckon they’ll be able to start making things like textures and increased stiffness.