Reconfigurable ultrasound focusing effect through acoustic barriers

• Published in: Ultrasonics 2025-01, Vol.145, p.107470, Article 107470
• Main Authors: Ma, Ming, Gao, He, Guo, Xinze, Su, Zhongqing
• Format: Article
• Language: English
• Subjects: Acoustic meta-lens; Inverse design; Reconfigurable focusing; Transmission enhancement
• ISSN: 0041-624X; 1874-9968; 1874-9968
• DOI: 10.1016/j.ultras.2024.107470

•A novel meta-lens for enhanced ultrasound focusing and energy transmission through acoustic barriers.•An inverse design methodology capitalizing on the advantages of acoustic-structure interactions.•A focal length that can be manipulated by adjusting each unit height while maintaining high transmission efficiency.•An optimized meta-lens enabling high-efficiency transmission of ultrasonic energy via arbitrarily shaped layers. The low transmission efficiency of ultrasonic waves in waveguides of a high acoustic impedance (referred to as dense materials), due to the impedance mismatch between the background media and the dense materials, poses a significant obstacle to practical applications of high-intensity focused ultrasound (HIFU) such as ultrasound therapy or medical imaging. To address this challenge, we present an inverse optimization scheme for fabrication of novel acoustic meta-lenses, enabling strengthened penetration and enhanced focusing of ultrasonic waves when the waves traverse barriers. Both simulation and experiment validate the effectiveness of the developed meta-lenses which are annexed to hemispherical plates, and demonstrate an enhanced transmission of the sound power by an order of magnitude compared to a scenario without the use of the meta-lens. The focal distance is reconfigurable by adjusting the geometric parameters of the meta-lenses. The proposed design philosophy is not restricted by the complexity of the target structures, and it allows the ultrasonic waves to pass through acoustic barriers with a non-uniform thickness yet maintaining efficient wave focusing. This study holds appealing applications in HIFU-enabled ultrasound imaging and therapy.