Mechanically Reinforced and Acoustically Transparent Ultrasound Interfaces via Conformal Densification of Physically Blended PDMS–PVA Composites

Abstract

Acoustically transparent interface materials that maintain both mechanical durability and signal fidelity are essential for stable operation of biomedical ultrasound transducers and related acoustic applications. Although polydimethylsiloxane (PDMS) is widely used for ultrasound encapsulation, PDMS acoustic interfaces are sensitive to thickness nonuniformity on curvilinear surfaces, leading to reduced mechanical properties and unstable signal variability. Poly(vinyl alcohol) (PVA) is a hydrophilic polymer with abundant hydroxyl groups and can contribute to morphological stabilization in physically blended polymer systems. Herein, we introduce a physically blended PDMS–PVA composite acoustic interface that enhances conformal contact and interfacial integrity while preserving acoustic transparency. PDMS–PVA showed a 5.3-fold increase in viscosity and a 58% reduction in pore volume compared with PDMS, enhancing surface conformity and structural integrity. Mechanical characterization revealed that structural densification significantly increased the ultimate tensile strength to 8.3 MPa and improved fracture resistance, demonstrating robust tolerance to physical deformation. Despite these mechanical enhancements, acoustic impedance (∼1.25 MRayl) was preserved, enabling efficient signal transmission suitable for biomedical imaging and precise control. Consequently, the PDMS–PVA composite provides a rigid-particle-free route to mechanically reinforced protective ultrasound interfaces that preserve acoustic impedance and signal-transmission characteristics.