Enhanced Ultrasound Transmission Through Aberration Layers Using Space‐Coiling Acoustic Metamaterials

Ultrasound is widely used in medical imaging and therapy. Yet its performance is limited by layers such as the skull or calcified tissue that exhibit an impedance mismatch with the background medium. As a result, wave energy scatters, phase distorts, and overall transmission decrease. To address this, we explore a space‐coiling metamaterial that can enhance transmission through aberration layers. The coiled‐path design is optimized based on geometric parameters. Finite element simulations demonstrate enhanced transmission through an aberration layer near 4 MHz with water as the background medium. Further analysis shows negative effective properties, which could serve as a complementary layer. To validate this design, a scaled‐up prototype was fabricated using fused‐silica microfabrication and experimentally tested in a water tank. The measured transmission spectrum shows an enhancement around 450 kHz, matching the expected frequency shift due to geometric scaling. The experimental results exhibit agreement with the numerical predictions, confirming that the enhancement mechanisms, resonant tunneling, and impedance compensation remain effective across different scales. These findings show the potential of space‐coiling metamaterials to improve ultrasound transmission through impedance‐mismatched layers and support practical implementation. Future work will focus on further experimental validation and integration of such structures into ultrasound systems, including linear‐array probes.