Dynamic ultrasound achromatic imaging with a stretchable flexible metalens

Ultrasound imaging is widely used in both engineering and medicine due to its advantages of deep penetration and no ionizing radiation. Focusing techniques can improve image resolution, but conventional methods often suffer from chromatic aberration. We present a novel approach to ultrasound imaging that overcomes this challenge, which utilizes a stretchable flexible metalens to experimentally achieve dynamic achromatic imaging. By carefully stretching and releasing the metalens, we can focus ultrasound of different frequencies at the same depth. This method features remarkable focusing resolutions of 0.6λ in the radial direction and 2.3λ in the axial direction, and a 13% deformation of the metalens enables effective compensation for chromatic aberration of ultrasound from 0.81 MHz to 1 MHz. Furthermore, we demonstrate the dynamic achromatic imaging of microstructures, showcasing its ability to capture high-resolution ultrasound images.