Lamb wave-based acoustofluidics

Both bulk acoustic wave (BAW) and surface acoustic wave (SAW) acoustofluidic technologies have been widely utilized for particle manipulation. However, within fluid, these waves tend to propagate as bulk waves or leaky bulk waves, resulting in undesirable acoustic streaming that causes unstable particle manipulation. Here, we introduce a novel Lamb wave-based acoustofluidic device for precisely trapping and levitating microparticles. The device consists of a piezoceramic plate coated with a one-dimensionalperiodic array of electrodes on one side, while the other side features a continuous electrode layer. By optimizing the electrode periodicity and plate thickness, we can efficiently excite two resonant modes: the non-leaky zero-order asymmetric (A0) Lamb waves, which are characterized by a highly periodic localized field, and the Wood's anomaly mode, which exhibits a periodic but weaker localized field. We fabricated the device and conducted experiments to manipulate particles suspended in water on the plate's surface, successfully achieving periodic trapping and levitation, as well as controlled movement of trapped or levitated particles by adjusting the phase of the source. The innovative approach to particle manipulation using Lamb waves advances the development of compact acoustofluidic systems with high precision, high throughput, and low energy consumption.