A Highly Stretchable Multilayer Circuit for Flexible Ultrasound Transducer

A highly stretchable multilayer circuit was developed using Cu-Be alloy serpentine interconnects for flexible ultrasound (FUS) transducer arrays. The stretchable multilayer circuit was fabricated using laser etching, vertical via, and silicone rubber composite encapsulation. FEM simulations and tensile tests show that serpentine interconnects with θ = 225° achieved a maximum elastic strain of 38.51% and a maximum strain limitation of 175%. An LED integrated with the stretchable circuit maintains consistent brightness under 50% strain, confirming its electrical resistance stability during tensile deformation. The linear FUS transducer with center frequency of 6.4 MHz is successfully developed. The pulse-echo response exhibits that -6 dB bandwidth of 62%. This work provides a scalable and reliable integration strategy for stretchable multilayer circuits in flexible ultrasound systems, with potential applications in continuous, conformal, and wearable medical imaging.