Ultrasound can do a whole lot more than create images of unborn babies. Since it first became a near-indispensable medical tool in the 1930s, technology that produces sound waves so high-pitched that humans can't hear them has found use in almost every branch of industry. The vibrations it creates can kill bacteria, weld plastics and even help to mature brandies in a matter of days rather than years. Today, ultrasound is finding its way into even more applications, powering inventions that have the potential to make huge changes in their fields. We are on the brink of a real contactless alternative to touch-screen technology.

When most people think holograms, they think of a floating image, a 3D projection of light. But scientists have designed technology that replaces light in the hologram with sound, giving us acoustic holograms that can be used to manipulate small objects. Researchers from the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, have created these acoustic holograms by first printing a hologram plate using a 3D printer, and then transmitting ultrasound waves through it and into another medium, which could be liquid or gas. The uneven surface of the plate causes phase delays in the waves which affect the medium and therefore other objects or particles suspended in or on it. Peer Fischer, who usually works on tiny robots, was "looking for a way to move large numbers of microparticles simultaneously so that we could assemble them into larger more complex structures" when his team came up with acoustic holography, he said in a statement.