Particulate material suspended in a fluid is separated and recycled by means of an ultrasonic resonance wave. In a preferred embodiment, the ultrasonic resonance field is generated within a multilayered composite resonator system including a transducer, the suspension and a mirror parallel...http://www.google.ca/patents/US5711888?utm_source=gb-gplus-sharePatent US5711888 - Multilayered piezoelectric resonator for the separation of suspended particles 
