"Think about a flute," said Fang, a member of the Molecular and Electronic Nanostructures research initiative at Beckman. "When we play music we are using some instrument that carries sound waves, and yet each of those buttons are much smaller than the wavelengths they produce.
"So here we take a similar philosophy. We're using very tiny elements, tiny resonator cavities, and in an analog to the flute, we try to create those structures in order to manipulate or control the resonating frequencies of ultrasound."
Fang's work for his Ph.D. and as a postdoc primarily revolved around photonic materials and devices and 3-D fabrication. He specifically has focused on improving nanoscale microscopy through superlensing, which greatly enhances the scope and image resolution of traditional microscopes by incorporating layered nanomaterials in the imaging process.
Now he is applying those principles to acoustics, a new research line that is described in his paper "Ultrasonic metamaterials with negative modulus" that appears for the first time in today's online edition of Nature Materials. Fang is interested in developing new classes of ultrasound materials with a series of unique physical phenomena, such as negative refraction and super-resolution focusing.
Fang said superlensing is used to image subwavelengths, structures along the size of 50 nanometers, or about 1/8th the size of a normal optical wavelength. Applying those methods to acoustical waves could, for example, produce much higher resolution ultrasound images.
"Here we're adapting the same philosophy to build materials that do as good a quality for acoustical waves," Fang said. "Here we are talking about a totally different wave. It's something we can probably use for medical screening."
Fang said the method could improve the resolution of ultrasound images without increasing the risk to patients. Tumors, for instance, could be caught at their earliest stages.
Other applications could include non-destructive testing in industry for quality control, such as acoustical searches for stress fractures in building materials.
Both superlensing and ultrasonic metamaterials, Fang said, are about "improving the application's capabilities."
Fang is an Assistant Professor of Mechanical and Industrial Engineerign at the University of Illinois at Urbana-Champaign.