Scientists in England have harnessed the power of sound to levitate small objects — a development that could lead to medical advances.
Researchers at the University of Bristol have used "acoustic tractor beams" to suspend items in the air, including ants.
They used 250 tiny loudspeakers to generate ultrasound that's too high-pitched for the human ear to detect.
By adapting the sound they have been able to manouever objects around an obstacle course for the first time.
Dr Asier Marzo, a researcher at the University of Bristol, said the technology may one day be applied to medicine.
"You may have a kidney stone and it's very painful," he said. "The advantage of this thing is that you don't need to cut anything, you don't need any incision into the body. You would apply the device from the outside. It's like an invisible hand that will go inside your body, pick the particle and move it up. "
Bruce Drinkwater, a professor of ultrasonics at the university, describes it like an invisible robot.
"It's a force field that can apply and do different functionalities," he said. "So, it's like a pair of hands — or a robot pair of hands — except there is no robot. It's purely a force field that's applying the required position, rotation and then moving things into position. "
The technique appears to have no harmful side effects, so far. The levitating ant crawls away afterwards, seemingly unaffected.
But human levitation appears to be some way off.
The rig would need to be scaled up to 40,000 speakers, producing 10-times more sound energy to levels that are harmful to humans, as it would require dangerous levels of energy that may be converted into heat.