A Fresnel Annular Sector Actuator (FASA) for micromixing of fluids, utilizes a self-focusing acoustic wave transducer which focuses acoustic waves through constructive wave interference. In the transducer, RF power is applied between the electrodes (sandwiching a piezoelectric film) with its frequency preferably corresponding to the thickness mode resonance of the piezoelectric film. Strong acoustic waves are generated over the electrode area, and interfere with each other as they propagate in the fluid. By proper design of the electrodes, and forming various combinations of the electrodes, wave focusing can be achieved. The mixing can be further enhanced by providing selective actuation and sequencing of the different segments by an RF signal source.