MEMS Bessel Beam Acoustic Transducer (MEMS-BBAT) with Air-Cavity Lens Based on Spiral Diffraction Grating for Particle Trapping

The paper proposes a compact Bessel beam acoustic transducer (BBAT) using MEMS technique. Encoding the first order Archimedean spiral grating with air-cavity lens on 1mm thick bulk lead zirconate titanate (PZT), the transducer generates first order acoustic Bessel beam which exerts lateral radiation force on objects with positive impedance contrast to the center of wavefront. In addition, the first order Bessel beam transports angular momentum, thus yields acoustic streaming in the propagate direction. The fabricated transducer acting as acoustic tweezer is demonstrated to trap Polystyrene (PS) particle on water surface and within water in the center of wavefront by the lateral acoustic radiation force and acoustic streaming.