News & Analysis
/
Article

Layered metamaterial offers enhanced ultrasonic imaging

SEP 17, 2018
A porous metamaterial lens achieves subwavelength resolution without anomalous dips in transmission.
Layered metamaterial offers enhanced ultrasonic imaging internal name

Layered metamaterial offers enhanced ultrasonic imaging lead image

Metamaterials manipulate waves using a carefully crafted pattern of cavities, and waves traversing a metamaterial can be bent, focused and even amplified depending on the geometry of these internal structures. Up until now, work on metamaterials has primarily considered periodic arrangements of holes to allow for these wave-shaping properties. But such approaches suffer from frequency-dependent dips in transmission known as Wood’s anomalies.

Recent work by Amireddy and collaborators reported on a metamaterial lens capable of subwavelength imaging of ultrasonic waves — a common tool for medical diagnostics and even treatments. Now, the same authors have described a new multilayered metamaterial lens fashioned from an aperiodic pattern of holes capable of resolving structures less than 3 percent the size of an ultrasonic wave. The result, which improves the resolution of their prior method by 30 percent, also limits the impact of Wood’s anomalies.

To characterize their lens, the authors excited ultrasonic waves in two aluminum blocks, each featuring different subwavelength structures. By measuring the amplitude of waves transmitted from the block through the metamaterial lens, they were able to clearly image the small structures in their samples — features that didn’t appear when the metamaterial lens was absent.

They also compared the operation of their lens to a simulated six-layer metamaterial, finding a qualitative agreement between the transmission properties of the two. A closer analysis of the transmission through the simulated lens revealed different frequency dips in each layer, suggesting that the total transmission washes out the effect of Wood’s anomalies in individual layers.

Source: “Porous metamaterials for deep sub-wavelength ultrasonic imaging,” by Kiran Kumar Amireddy, Krishnan Balasubramaniam, and Prabhu Rajagopal, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5045087 .

Related Topics
More Science
/
Article
Using an iterative approach based on ocean data combined with typhoon trajectory inversion methods significantly improves accuracy over existing methods.
/
Article
Characterizing calcium diffusion during the basic spherification method will optimize the production of beverage pearls.
AAS
/
Article
When a gas cloud collapses to form a star cluster, how many objects form, and what are their masses? Research published today provides answers about the low-mass end of the star and brown dwarf formation process.
AAS
/
Article
A late-night total eclipse of the Moon highlights the coming week, and never mind that this is a minimoon. Sirius holds the meridian at nightfall, just as the Winter Triangle tips to balance on its brightest point.