AC Electrokinetics of Physiological Fluids for Biomedical Applications

Abstract

Alternating current (AC) electrokinetics is a collection of processes for manipulating bulk fluid mass and embedded objects with AC electric fields. The ability of AC electrokinetics to implement the major microfluidic operations, such as pumping, mixing, concentration, and separation, makes it possible to develop integrated systems for clinical diagnostics in nontraditional health care settings. The high conductivity of physiological fluids presents new challenges and opportunities for AC electrokinetics-based diagnostic systems. In this review, AC electrokinetic phenomena in conductive physiological fluids are described followed by a review of the basic microfluidic operations and the recent biomedical applications of AC electrokinetics. The future prospects of AC electrokinetics for clinical diagnostics are presented.

Keywords: electrokinetics; electrothermal flow; microfluidics; physiological fluid; point-of-care diagnostics.

Figure 1

(A) Schematic of AC electrothermal flow. Arrows induced the direction of the bulk fluid force and fluid circulation. (B) The frequency dependence of the electrothermal force, M(ω,T), at different fluid conductivities.

Figure 2

(A) Principle of dielectrophoresis. B) Modeling of dielectric responses of red blood cells (RBC) and E. coli in media of different conductivities.

Figure 3

Schematic illustration of six AC electrothermal pump designs. (A) Asymmetric electrodes design, (B) DC-biased AC electrothermal pump, (C) AC electrothermal pump with an external heating element, (D) enhanced AC electrothermal pumping with thin film resistive heaters embedded, (E) traveling-wave AC electrothermal pump, and (F) AC electrothermal fluidic pumping in micro-grooved channels

Figure 4

Schematic illustrations of electrode configurations for fluid mixing by AC electrothermal effect with (A) symmetric electrodes with AC voltage and DC bias, and (B) asymmetric meandering electrodes with AC voltage. Schematic illustrations of (C) AC electrothermal enhancement of heterogeneous assays, and (D) AC electrothermal enhancement of an electrochemical pathogen sensor.

Figure 5

Bioparticle manipulation: Schematic illustrations of (A) nanoscale bioparticle trapping, (B) DEP-based single-cell patterning for patterning, proliferating, and/or migrating cells, continuous cell (C) separation and (D) concentration, hybrid electrokinetic device for manipulating (E) bacteria and (F) cancer cells (focusing and separation).