Field-effect pump: liquid dielectrophoresis along a virtual microchannel with source-gate-drain electric fields

Abstract

We investigate liquid dielectrophoresis (LDEP) to implement field-effect pumps (FEPs) that drive liquids from source, via gate, toward drain electric fields between parallel plates without external pumps or the problem of dead volume. The appropriate gate electric field establishes a wall-less virtual microchannel to transfer the liquid from source to drain with an adjustable flow rate (Q) controlled by the difference of the square of the electric field strength (ΔE²_DS). Analogous to field-effect transistors (FETs), the FEPs can operate in a “linear”, “transition” or “saturation” region depending on ΔE²_GD and ΔE²_DS. With a sufficient ΔE²_GD and a small ΔE²_DS, the FEPs operated in the linear region where Q was linearly proportional to ΔE²_DS and inversely proportional to the flow resistance R that was mainly determined by the length (L), width (W) and height (H) of a stable and fully-occupied virtual microchannel. With an insufficient ΔE²_GD and a moderate to large ΔE²_DS, narrowing, tapering and even pinch-off of virtual microchannels were observed, which increased R and changed the operation into the transition or saturation region. A field-effect stream merger regulating two streams was built based on two FEPs with shared gate and drain electrodes. The versatility of FEPs was demonstrated with preliminary studies on whole blood and particle solutions.