Metamaterial produces high-resolution ultrasound images

Wayne Dickson, PhD, and his colleagues at King's College London (www.kcl.ac.uk) have developed a new metamaterial that could be used to develop novel sensors for ultrasound imaging systems, enabling them to produce high-resolution images.

Conventional piezoelectric-based ultrasound sensors convert ultrasound waves into electrical signals from which images are reconstructed. However, these types of sensors are limited in bandwidth and sensitivity-limitations that have been the primary obstacle preventing high-quality images from being obtained.

An acousto-optical sensor that employs the metamaterial developed by Dickson would not be subject to such limitations, primarily because it converts the ultrasound waves into optical signals.

Ultrasound waves interact with the metamaterial that consists of gold nanorods embedded in a polymer known as polypyrrole (PPy). Light from a laser impinging on the metamaterial is modulated by pressure-induced changes in the material.

By comparing the intensity of the reflected light from the metamaterial with the ultrasonic wave, it is possible to reconstruct high-quality, high-resolution images. The improvement in sensitivity may enable ultrasound devices to see previously undetectable details, an advance that could significantly bolster a technology employed in a variety of biomedical applications.