Microfluidic Release of the Rare Cells Captured by a Filter with Tapered Holes

Rare cells such as circulating tumor cells and prenatal fetal cells can be captured by size-dependent filtration using a microfluidic device. Herein, we report a method to release the captured cells with the same microfluidic device which consisted of a microfabricated filter with tapered holes. When a cell containing flow passed through the filter, the cells could be blocked by the filter. Afterward, a reverse flow was applied to release the captured cells. To increase the efficiency of the capture and the release, a filter with tapered holes was used and micro-particles of sizes between smaller and large hole diameters were added into the reverse flow. We found that when the majority of the holes were blocked, the trans-filter flow resistance drastically increased and most of the captured cells could be released. As a proof of concept, ovarian cancer cells SKOV3 were used, showing a high release efficiency and remarkable viability of the collected cells.