Method can levitate just about anything

Levitation may look like magic, but there are a number of scientific tricks behind it. Magnetic systems are usually behind gimmicky consumer products like floating lightbulbs and speakers, optical levitation turns up in more academic pursuits like quantum computing, and acoustics could help suspend tiny particles to make better drugs. These techniques only work with certain objects, but researchers at the University of Chicago have developed a method to levitate basically anything, using differences in temperature.

“Magnetic levitation only works on magnetic particles, and optical levitation only works on objects that can be polarized by light, but with our first-of-its-kind method, we demonstrate a method to levitate generic objects,” says Cheng Chin, one of the researchers on the team.

Balls of ceramic, plastic and glass, ice particles, seeds and pieces of lint have been used to demonstrate the technique, and the team found that the levitated particles could be held aloft for over an hour rather than a matter of minutes, and wouldn’t wobble around sideways.

The researchers achieved this versatile levitation through the process of thermophoresis, which manipulates particles by placing them between sources of different temperatures. In this case, the objects were placed in a vacuum between two plates – the bottom one, made of copper, was left at room temperature, while the top plate contained liquid nitrogen, cooling a stainless steel container to -300º F (-184º C). The relative heat would flow from the bottom plate toward the top one, lifting the particles along with it.

“The large temperature gradient leads to a force that balances gravity and results in stable levitation,” says Frankie Fung, lead author of the study. “We managed to quantify the thermophoretic force and found reasonable agreement with what is predicted by theory. This will allow us to explore the possibilities of levitating different types of objects.”