Enhanced contactless dielectrophoresis enrichment and isolation platform via cell-scale microstructures

We designed a new microfluidic device that uses pillars on the same order as the diameter of a cell (20 µm) to isolate and enrich rare cell samples from background. These cell-scale microstructures improve viability, trapping efficiency, and throughput while reducing pearl chaining. The area where cells

trap on each pillar is small, such that only one or two cells trap while fluid flow carries away excess cells. We employed contactless dielectrophoresis in which a thin PDMS membrane separates the cell suspension from the electrodes, improving cell viability for off-chip collection and analysis. We compared viability and trapping efficiency of a highly aggressive Mouse Ovarian Surface Epithelial (MOSE) cell line in this 20 µm pillar device to measurements in an earlier device with the same layout but pillars of 100 µm diameter. We found that MOSE cells in the new device with 20 µm pillars had higher viability at 350 VRMS, 30 kHz, and 1.2 ml/h (control 77%, untrapped 71%, trapped 81%) than in the previous generation device (untrapped 47%, trapped 42%). The new device can trap up to 6 times more cells under the same conditions. Our new device can sort cells with a high flow rate of 2.2 ml/h and throughput of a few million cells per hour while maintaining a viable population of cells for off-chip analysis. By using the device to separate subpopulations of tumor cells while maintaining their viability at large sample sizes, this technology can be used in developing personalized treatments that target the most aggressive cancerous cells.

20 μm pillar contactless dielectrophoresis device. (a) Top view photo and (b) exploded schematic of a cross section across a row of pillars with white space added to visually separate layers. The main channel is colored green and contains inlets for both cell suspension and DEP buffer. Electrode channels are colored purple, they are filled with 10 × PBS and connected to the high voltage generator. An electric field is applied across each chamber, perpendicular to the direction of fluid flow.

Photo of trapped cells in cDEP devices. Direction of fluid flow is from top to bottom, while electric field is applied horizontally. (a) High density of cell suspension in a device with large (100 μm) pillars results in pearl-chaining and unspecific trapping. (b) In a device with small 20 μm pillars only one or two cells can trap on each pillar. When saturated, excessive cells will not accumulate, but continue to next available location.