Dielectrophoretic cell sorting with high velocity enabled by two-layer sidewall microelectrodes extending along the entire channel

Abstract

Dielectrophoresis has been widely applied in microfluidic cell separation, and it enables label-free and size-independent cell sorting based on their dielectric fingerprints which is prerequisite for downstream biomedical analysis. The linear flow velocity and cross-sectional area are the two key factors proportional to the flow rate and thus directly related to the sample processing throughput. Aiming at higher flow rate, the state-of-art techniques mostly focus on the cross-sectional area, either by using wide chamber with angled electrode digits or 3D volumetric electrodes with expanded channel depth. On the other hand, the velocity is always carefully limited because cells have very squeezed time to interact with the DEP force that drives them to migrate, and the flow drag induced by high velocity potentially poses adverse effect against the DEP-driven cell migration. In this paper, we present DEP-activated cell sorting at high-velocity being 1–2 orders of magnitude higher than the existing DEP separators, which is enabled by easily-fabricated two-layer 3D sidewall electrodes extending along the entire flow channel. Such electrodes project DEP force fully decoupled from the flow drag, and acting on cells continuously, allowing sufficient time for cell migration. The two-layer design leads to cell migration across a shorter distance between the upper and lower layers, with a unique bridge adaptor evolved at the downstream for the collection of the cells vertically separated. The DEP device achieves separation of live and dead yeast cells at high velocity up to 78.3 mm/s, more than a full order of magnitude higher compared to any reported DEP platforms. This velocity corresponds to a competitive flow rate of 3.1 mL/h given the fairly small cross-sectional area, where the averaged collection rate is over 95 %. For the separation between the live and dead Hela cells, our device enables a high velocity up to 50.5 mm/s with an averaged collection rate of ∼85 %. A high throughput of 1.79 × 1 0^(5) cells/min for the live and dead Hela cell separation has been achieved with 89.7 % collection for live cells and a velocity of 30.3 mm/s.