High‐Performance and Environmentally‐Friendly Bulk‐Wave‐Acoustofluidic Devices Driven by Lead‐Free Piezoelectric Materials

Bulk-wave-acoustofluidic devices provide strong acoustic fields and high device efficiency, thereby offering high-throughput capability when processing biological samples. Such devices are typically driven by lead zirconate titanate (PZT) transducers, which contain a high content of lead, inevitably resulting in environmental and biocompatibility issues. Replacing PZT with lead-free piezoelectric materials in various ultrasonic devices is considered challenging mainly due to the inferior piezoelectric properties lead-free materials possess compared to those of PZT. In this study, through both experiments and numerical simulations, it is demonstrated that the performance of the bulk-wave-acoustofluidic devices driven by (Bi,Na)TiO₃-BaTiO₃-(Bi,Na)(Mn,Nb)O₃ (BNT-BT-BNMN) can match that of PZT-driven devices at low power and is superior at intermediate power. It is found that the low acoustic impedance and the weak transverse mode in BNT-BT-BNMN compensate for the inferior piezoelectric properties at low power. The fact that the BNT-BT-BNMN devices outperform at intermediate power is consistent with the superior performance of the Mn-doped BNT-based piezoelectric materials compared to PZT at high power. Perfect focusing on 5- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>μ</mml:mi> <mml:mi>m</mml:mi></mml:mrow> <mml:annotation>$\mathrm{\umu}\mathrm{m}$</mml:annotation></mml:semantics> </mml:math> -diameter polystyrene particles at a flow rate of up to 10 mL min^-1 is achieved using the BNT-BT-BNMN device at input power of 1 W.