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Circulating Tumor Cell Filter

Device and Operation

Having designed the adjustable filtration mechanism, it was time to implement it in a full device capable of separating a large volume of cells. We wanted a device capable of processing 1 million cells/hour and providing at least an enrichment factor of 1000 - that is, the ratio of cancer cells : blood cells at the output should be 1000x greater than at the input. We also wanted to be able to collect cells from the outlet via micropipette aspiration.

To these ends I chose a design with 32 parallel filters, connected by a bifurcation network. The outlets are 5mm punched holes, large enough to accommodate a micropipette to suck up the cells afterwards. In the picture below, the red channels carry the cells to be sorted while the dead-end green channels exist to create valves where the overlap with the red.

The device, filled with food coloring for visibility. The layer that carries the cells is shown in red, and the layer used to actuate the valves and filter is shown in green.

The device runs on a repeating three step cycle. In simplest terms:

1. Filter - Run your sample through the filters, catching a bunch of cells
2. Purge - Push buffer fluid through the device to eliminate any stragglers not trapped in the filters
3. Collect - Relax the filter to release the captured cells and flow them into your collection outlet

The operational cycle of the device, showing the state of the valves and filters at each step.

With this in mind let's take another look at the video. In the video we'll see two views side by side - on the left is a closeup of one of the 32 filters, and on the right is a more zoomed out view of the channels leading to the two outlets. During the video the device is separating a mixture of blood cells and bladder cancer cells. To help differentiate between them we stained the blood cells blue and the cancer cells green.

Microscopy video showing a mixture of cells being separated by the device. I suggest you switch to fullscreen to better see the cells.