Methods, compositions, and automated systems for separating rare cells from fluid samples

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 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 port for collecting enriched rare cells that can reversibly engage said antechamber via said inlet.

An automated fluid volume sensing system for determining the level of a sample or a portion of a sample, comprising:

• at least one bar in an essentially horizontal orientation, that is positioned or can be positioned proximal to a rack or sample holder, wherein said bar comprises:
• a light source on one end of said bar and a light sensor on another end of said bar, wherein the vertical level of the bar corresponds to the vertical level of the light source;
• wherein when a sample is in said rack or sample holder, said light source is positioned on one side of said sample, and said light sensor is positioned on the opposite side of said sample;
• further wherein said bar can move in a vertical direction, to allow said light source and said light sensor to scan a sample held in said rack or sample holder.

An automated fluid volume sensing!fluid volume uptake system for determining a volume of a sample supernatant in a sample tube or vessel and removing said volume of a sample supernatant from said sample tube or vessel, comprising:

• at least one bar in an essentially horizontal orientation, that is positioned or can be positioned proximal to a rack or sample holder,
• wherein said bar comprises:
• a light source on one end of said bar and a light sensor on another end of said bar, wherein the vertical level of the bar corresponds to the vertical level of the light source;
• wherein when a sample is in said rack or sample holder, said light source is positioned on one side of said sample, and said light sensor is positioned on the opposite side of said sample;
• further wherein said bar can move in a vertical direction, to allow said light source and said light sensor to scan a sample held in said rack or sample holder;
• a collection tip, wherein said collection tip is comprises a conduit for the uptake and dispensing of fluid, further wherein said collection tip can move in a horizontal plane, to position itself over a tube in said rack or holder, and can move in a vertical plane, to reach the level of the bar or a level within said sample tube.