A filtration unit, comprising: a filtration chamber, wherein said filtration chamber comprises an antechamber and a post-filtration subchamber separated by one microfabricated filter comprising one or more tapered pores, wherein said filtration chamber can rotate within said filtration unit between O and approximately 360 degrees, wherein said filtration chamber can rotate within said filtration unit approximately180 degrees or more; wherein said antechamber comprises an inlet and wherein said post-filtration subchamber comprises an outlet and at least one side port; a frame comprising: a loading reservoir; at least one sample loading valve that can provide fluid communication between said loading reservoir and said filtration chamber; at least one waste port that can reversibly engage said post-filtration subchamber via said outlet; and at least one collection port for collecting enriched rare cells that can reversibly engage said antechamber via said inlet; characterised in that when said filtration unit is in the filtering position, said antechamber is above said post-filtration subchamber, said inlet of said antechamber engages said at least one sample loading valve, and said outlet of said post-filtration subchamber engages said waste port; and further wherein, when said filtration unit is in the collection position, said post-filtration subchamber is above said antechamber, said inlet of said antechamber engages said collection port, and said outlet of said post-filtration subchamber is blocked. a filtration chamber, wherein said filtration chamber comprises an antechamber and a post-filtration subchamber separated by one microfabricated filter comprising one or more tapered pores, wherein said filtration chamber can rotate within said filtration unit between O and approximately 360 degrees, wherein said filtration chamber can rotate within said filtration unit approximately180 degrees or more; wherein said antechamber comprises an inlet and wherein said post-filtration subchamber comprises an outlet and at least one side port; a frame comprising: a loading reservoir; at least one sample loading valve that can provide fluid communication between said loading reservoir and said filtration chamber; at least one waste port that can reversibly engage said post-filtration subchamber via said outlet; and at least one collection port for collecting enriched rare cells that can reversibly engage said antechamber via said inlet; a loading reservoir; at least one sample loading valve that can provide fluid communication between said loading reservoir and said filtration chamber; at least one waste port that can reversibly engage said post-filtration subchamber via said outlet; and at least one collection port for collecting enriched rare cells that can reversibly engage said antechamber via said inlet; characterised in that when said filtration unit is in the filtering position, said antechamber is above said post-filtration subchamber, said inlet of said antechamber engages said at least one sample loading valve, and said outlet of said post-filtration subchamber engages said waste port; and further wherein, when said filtration unit is in the collection position, said post-filtration subchamber is above said antechamber, said inlet of said antechamber engages said collection port, and said outlet of said post-filtration subchamber is blocked.