Dual-mode Shear Horizontal / Rayleigh-like surface-acoustic-wave configuration on lithium niobate 64° Y-cut

Technologies based on surface acoustic waves (SAWs) find widespread use in wireless communications, signal processing, and sensing applications. In this study, we present an innovative dual-mode SAW configuration using a 64◦ Y-cut lithium niobate (LN) substrate. The conventional setup, employing interdigital transducers (IDTs) oriented along the crystal X-axis, is known for generating the shear horizontal mode (SH-SAW) with in-plane polarization. Conversely, by utilizing IDTs oriented perpendicular to the X-axis, we introduce effective excita- tion of a Rayleigh-like SAW (R-SAW), a novel achievement in our research. Through finite element simulations and electro-mechanical analyses, we comprehensively characterize these modes in terms of frequencies, polar- izations, propagation losses, and temperature coefficients. Furthermore, we investigate their interaction with liquids by analyzing damping characteristics and acoustic streaming effects using particle image velocimetry (PIV). SH-SAWs exhibit a leaky displacement during propagation with minimal damping in liquids, resulting in weak acoustic streaming—ideal for real-time sensing applications in wet environments. In contrast, non-leaky R- SAWs, characterized by a strong displacement component normal to the surface, exhibit enhanced acoustic streaming, facilitating microfluidic operations. Additionally, R-SAWs demonstrate high sensitivity to mass loading, making them optimal for real-time sensing in dry environments. The ability to generate both SAW modes on the same substrate offers the potential to develop fully electrical-driven, multifunctional integrated sensing platforms with SAW-driven microfluidic capabilities. This unique capability promises novel solutions in bio-sensing, leveraging the complementary strengths of the two acoustic modes in detection and sample handling.