Enhancing ultrasound transmission and focusing through a stiff plate with inversely optimized auxiliary meta-lens

Effective sound energy transmission and beam manipulation through stiff and dense materials such as metal remain daunting tasks. It is in part attributable to the vast impedance mismatch between those materials and ambient media. Adding openings may facilitate to better bridge energy over, yet ineffective in many applications and may also damage the structural integrity. Here, we present an auxiliary ultrasound focusing meta-lens for stiff and dense materials. It offers significantly enhanced ultrasound transmission and focusing through a stiff metal plate yet without enforcing any through holes or openings. The simple, one-sided only meta-structures are designed and optimized by an inverse strategy based on the genetic algorithm. We numerically and experimentally demonstrate the much enhanced ultrasound transmission when the meta-lens is added to a flat brass plate, along with the capability to offer simultaneous ultrasound focusing. This design methodology can be easily extended to deal with more complex shaped target in a straightforward manner, offering a practical solution to the efficient tunneling of ultrasound energy through stiff and dense materials. With simple grating structures, the meta-lens can be easily fabricated, showing great application prospects in medical imaging and disease treatment. Published under an exclusive license by AIP Publishing.

Automated summary

This study presents an auxiliary ultrasound focusing meta-lens for effective sound energy transmission and beam manipulation through stiff and dense materials. The meta-lens significantly enhances ultrasound transmission and focusing without the need for through holes or openings. The simple meta-structures are designed and optimized using a genetic algorithm. The meta-lens shows great application prospects in medical imaging and disease treatment.