Beads with functionalized material applied to them are exposed to an acoustic field to trap, retain or pass the beads. The beads may include or be free of ferro magnetic material. The beads may be biocompatible or biodegradable for a host. The size of the beads may vary over a range, and/or be heterogenous or homogenous. The composition of the beads may include high, neutral or low acoustic contrast material. The chemistry of the functionalized material may be compatible with existing processes. The acoustic field may be generated, for example, in an acoustic angled wave device or in an acoustic fluidized bed.