AC electroosmotic microconcentrator using a face-to-face,asymmetric electrode pair with expanded sections in the bottom electrode

An AC electroosmotic (AC-EO) microconcentrator using a face-to-face, asymmetric electrode pair with expanded sections in the bottom electrode is proposed in this study. The electrode pair of the AC-EO microconcentrator is composed of a larger top electrode (30 mm × 60 mm) and a bottom electrode (containing three slim electrodes and a triangular electrode). In the expanded section at the connection of a slim electrode and the triangular electrode, an electroosmosis flow transports test samples far away from the triangular electrode to the stagnation zone inside the triangular electrode through the slim electrode for concentration. On the three sides of the triangular electrode, vortices bring test samples surrounding the triangular electrode to the stagnation zone. By these two electroosmosis flow fields, the microconcentrator can concentrate test samples near and far from the triangular electrode to its central area, achieving a highly efficient sample concentration. The measured concentration distribution in the vertical electrode direction by confocal microscopy indicates that the concentration process occurs above the electrode surface. The capability of the proposed AC-EO concentrator in the repeated concentration and release of test samples is verified by a reversible switch test. The performance of the proposed AC-EO concentrator in concentrating latex particles and T4 GT7 DNA is better than those reported in the literature under similar average electric field strength. The fluorescence enhancement factor is 3.9–9.1 times better when concentrating latex particles, and the concentration enhance factor is 1.4–5.7 times better when concentrating T4 GT7 DNA.