Noise-robust high-fidelity ultrasound imaging with a flexible silicone-based metalens

Ultrasound imaging has been extensively employed in biomedical diagnosis and clinical research, owing to its compelling merits of non-ionizing radiation, cost-effectiveness, and real-time visualization. However, conventional ultrasound imaging systems are fundamentally constrained by diffraction-limited spatial resolution and insufficient conformability to complex biological tissue surfaces. Here, we design and fabricate a flexible Fresnel zone plate ultrasound metalens with transparent silicone-based materials, which is endowed with improved imaging resolution, excellent tissue conformability, and high acoustic-optical transmittance. Both experiments and simulations show that the proposed metalens achieves high-fidelity reconstruction of curved and linear contours from the letter-shaped ``D/F'' phantoms at 1 MHz. Further comparative imaging investigations on a customized ``CQNU'' pattern at 2 MHz demonstrate that the flexible metalens-based imaging method outperforms conventional plane-wave imaging in terms of ultrasound contrast and imaging quality. Additionally, the noise robustness of the metalens-based imaging system is evaluated by reconstructing a numeric target ``702489'' under varied input signal-to-noise ratios of 10 dB, 0 dB, and -10 dB. The well-resolved ultrasound images and quantitative imaging metrics manifest the remarkable noise tolerance and anti-interference capability of the metalens, enabling stable and high-quality imaging in complex, noisy biomedical scenarios. This flexible metalens-based imaging system holds great promise for advancing next-generation high-fidelity, conformal, and wearable ultrasound and photoacoustic bioimaging devices.