“…The flexibility of FFF results from the large number of potential transverse external fields that can be used. Gravitational [23,24], centrifugal sedimentation [25,26], electrical [27,28], magnetic [29,30], dielectrophoretic [31,32], acoustic [33,34], photophoretic [35,36], cross-flow (both symmetrical [37,38] and asymmetrical [39,40]) and thermal [41,42] fields have all been utilized by FFF. Cross-flows (both symmetrical and asymmetrical), sedimentation and thermal gradients are the most commonly-employed fields.…”