June 24, 2009

Scientists create first acoustic superlens

University of Illinois scientists say they have created the first acoustic superlens, an innovation that could impact several technologies.

The researchers, led by Professor Nicholas Fang, said their achievement could have practical implications for high-resolution ultrasound imaging, non-destructive structural testing of buildings and bridges, and underwater stealth technology.

The scientists said they successfully focused ultrasound waves through a flat metamaterial lens onto a spot about half the width of a wavelength at 60.5 kHz using a network of fluid-filled Helmholtz resonators.

According to the researchers, the acoustic system is analogous to an inductor-capacitor circuit. The transmission channels act as a series of inductors, and the Helmholtz resonators, which Fang describes as cavities that house resonating waves and oscillate at certain sonic frequencies almost as a musical instrument would, act as capacitors.

Fang said acoustic imaging is somewhat similar to optical imaging in that bending sound is similar to bending light.

But, compared with optical and X-ray imaging, creating an image from sound is a lot safer, which is why we use sonography on pregnant women, said Shu Zhang, who with Leilei Yin, a microscopist at the Beckman Institute, are co-authors of the study.

The research appeared in the May 15 issue of the journal Physical Review Letters.