A SAW-driven modular acoustofluidic tweezer.

In surface acoustic wave (SAW)-driven acoustofluidic tweezers (AFTs), most setups are integrated on a piezoelectric substrate for a single purpose, limiting the reusability and versatility of devices fabricated using complex MEMS technologies. Meanwhile, prevalent devices exhibit anisotropy in SAW excitation and propagation, as well as optical birefringence and limited transmittance. This work presents a SAW-driven modular acoustofluidic tweezer consisting of up to four replaceable interdigital transducer (IDT) modules and a function module assembled on a common base. Since the IDT modules are separated, each can be fabricated using the piezoelectric substrate best suited to the requirements. For example, SAWs generated from different directions can simultaneously propagate along the X-axis of 128° Y-cut LiNbO₃, enabling highly efficient excitations. The generated SAWs couple into the function module with excellent optical properties and convert into Lamb waves, which then leak into the microfluidic domain and act on the fluid/particles. All modules are connected via standardized interfaces, eliminating potential instabilities caused by wired connections. The reliability of the setup is demonstrated via particle/cell patterning, separation, and concentration experiments, during which the replaceability and reusability of different modules, and the other advantages of the setup, e.g., simple assembly, ease of operation, and application flexibility, are proven.