Thin LiNbO₃ Shear Horizontal Acoustic Plate Mode Biosensor

Traditional Quartz Crystal Microbalance (QCM) sensors used for biological detection are limited in mass sensitivity due to their large thickness. This study presents a biosensor utilizing a Shear Horizontal Acoustic Plate Mode (SHAPM) resonator constructed from a suspended Y+36° cut LiNbO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (LNO) plate. LNO is chosen over quartz or AlN for its higher permittivity, which reduces capacitive coupling when in contact with water. Finite Element Method (FEM) simulations reveal that mass sensitivity (S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf>) increases with decreasing LNO plate thickness, yet structural integrity limits the minimum thickness to 2 μm, resulting in S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> = 70 Hz•cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/ng. The device is integrated into a microfluidic system and a printed circuit board for real-time detection. The sensor exhibits a limit of detection (LOD) of 15 ng/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for non-specific binding of Bovine Serum Albumin (BSA). This is comparable to that of previously reported Love wave devices.