A new technology that can create an “acoustic bottle” in midair could improve ultrasound imaging, according to researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory in Berkeley, California. The technique also shows promise in a number of more exotic fields, including acoustic cloaking, particle manipulation, and levitation.
Our acoustic bottle beams open new avenues to applications in which there is a need to access hard-to-reach objects hidden behind obstacles, such as acoustic imaging and therapeutic ultrasound through inhomogeneous media. We can also use an acoustic bottle as a cloaking device, rerouting sound waves around an object and then recovering them in their original form, making the object invisible to sonar detection.
The “bottle” results from bending sound waves along a curved trajectory in open space. The waves are bent in three dimensions around a null pressure region in the middle, forming a bottle shape with a “quiet” space in the center. The sound is generated by an array of tiny loudspeakers.
Engineered nanoconstructs known as metamaterials can similarly bend sound waves. But the acoustic bottle doesn’t need help from physical materials. “Our technique offers a new degree of freedom for controlling the flow of acoustic energy at will,” said Dr. Zhang.
So what else can you do when you control the flow of acoustic energy at will? How about levitation? Using sound waves to manipulate particles, water droplets, and other minuscule objects is a hot field right now. One recent breakthrough put standing sound waves to work in 3-D printing. That’s nothing, said Jie Zhu, PhD, a co-author of the Nature Communications paper and a postdoctoral fellow at Berkeley Lab.
“Our acoustic beams can do the same thing but offer better stability, true 3-D graphics, and more freedom of movement, as our beam can propagate along a curved path,” Dr. Zhu said. “We can also levitate much larger 3-D objects than can be lifted and manipulated with other acoustic levitation techniques.”
Related CME seminar (up to 8 AMA PRA Category 1 credits™): Breast Ultrasound