Field-effect control of electro-osmotic flow in microfluidic networks

Electro-osmotic flow along superhydrophobic surfaces with embedded electrodes

“…The higher the viscosity of the medium filling the grooves, the greater σ f /σ w must be to achieve considerable velocity amplifications. This agrees with experiments on influencing electro-osmotic flow by embedded electrodes underneath a solid wall [34][35][36][37], i.e., the limiting case of very high viscosity, where very high voltages are needed in order to have any impact on the flow. Although the maximum charge density at the fluid-fluid interface may be higher for liquid-filled than for gas-filled grooves by the ratio of the permittivities of the groove-filling media, fluid permittivities are usually not large enough to compensate for the effect of viscosity.…”

Theoretical modelling of electrokinetic flow in microchannel networks

“…In systems driven solely by pressure, streaming phenomena occur when microchannels contain interfacial charge, and hence the electrokinetic ζ-potential is present (see, for instance [18]). Conversely, in systems driven by EOF, pressure differences take place if the ζ-potential varies from one branch to another [6], (b) cross-shaped [7], (c) multi-branch [8], (d) double-T [9], (e) double-cross [10], and (f) multi-junction [11]. References cited above are some of several examples found in the recent literature.…”

On hybrid electroosmotic kinetics for field‐effect‐reconfigurable nanoparticle trapping in a four‐terminal spiral microelectrode array

“…Although a series of ICEO particle manipulation approach has been reported, there is still a need to implement targeted enrichment of colloidal particles on a relatively broad scale. In view of this, we propose herein a unique physical concept of hybrid electroosmotic kinetics (HEK), in terms of bi‐phase ICEO (BICEO) with two applied AC voltage signals of 180° phase difference for switching the sample collection state in time at our wishes, as well as a more advanced version, termed as "AC field‐effect flow control on BICEO," in analogy to flow field‐effect‐transistor (flow‐FET) in microfabricated fluidic networks for realizing rectifications in DC electroosmotic (DCEO) pump flow. We make use of a spiral electrode array to construct the ideally polarizable interface for generating fast ICEO fluid motion in its vicinity, wherein four isolated electrode strips are in direct contact with electrolyte solution, so merely several volts are enough to actuate electrically the microfluidic device for position‐controllable particle concentration adjacent to the metal surface; this forms a stark contrast with the technique of flow‐FET developed most initially for DCEO, in which a relatively thick dielectric membrane incorporated in the three‐capacitor model results in the requirement of very high gate voltages (usually 50–1000 V), so as to accelerate appreciably the pump flow rate.…”