An integrated AC electrokinetic pump in a microfluidic loop for fast and tunable flow control.

We have built a dedicated lab on a chip to study the performance of an integrated electrokinetic micropump, driven by a low voltage AC signal. This micropump consists of an array of interdigitated electrodes and is here integrated in a microfluidic loop. We demonstrate that this device can pump continuously and reproducibly electrolyte solutions of low to moderate ionic strength. The pumping speed reaches up to 500 [micro sign]m s(-1) in 20 [micro sign]m deep and 100 [micro sign]m wide channels with a driving signal in the 1-10 kHz range and an amplitude of only a few volts. In addition, we have observed an interesting reversal of the pumping direction at higher frequencies (50-100 kHz). Our device permits a systematic and automated exploration of the influence of the ionic strength thanks to an integrated micromixer.