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

Abstract 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)TiO ₃ ‐BaTiO ₃ ‐(Bi,Na)(Mn,Nb)O ₃ (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‐‐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.