A microparticle and/or nanoparticle separation, filtration and/or enriching device. The device comprises a flow passage through which can be directed a liquid suspension supporting microparticles and/or nanoparticles therein, and at least one packed bed of particles physically retained within the flow passage through which can pass therethrough the liquid suspension. The device further comprises an ultrasonic actuation system for mechanically activating the or each packed bed during passage therethrough of the liquid suspension.