On the recent developments of insulator‐based dielectrophoresis: A review

Abstract

Insulator-based dielectrophoresis (iDEP), also known as electrodeless DEP, has become a well-known dielectrophoretic technique, no longer viewed as a new methodology. Significant advances on iDEP have been reported during the last 15 years. This review article aims to summarize some of the most important findings on iDEP organized by the type of dielectrophoretic mode: streaming and trapping iDEP. The former is primarily used for particle sorting, while the latter has great capability for particle enrichment. The characteristics of a wide array of devices are discussed for each type of dielectrophoretic mode in order to present an overview of the distinct designs and applications developed with iDEP. A short section on Joule heating effects and electrothermal flow is also included to highlight some of the challenges in the utilization of iDEP systems. The significant progress on iDEP illustrates its potential for a large number of applications, ranging from bioanalysis to clinical and biomedical assessments. The present article discusses the work on iDEP by numerous research groups around the world, with the aim of proving the reader with an overview of the state-of-the-art in iDEP microfluidic systems.

Recent advances in direct current electrokinetic manipulation of particles for microfluidic applications

“…A hydrodynamic pumping of the particulate solution, which is required in nearly all other field control methods, thus becomes unnecessary in DC electric field‐mediated applications . If the microchannel is geometrically nonuniform or nonstraight, DC electric fields can also generate a dielectrophoretic particle motion, which is the underlying mechanism of the rapidly growing insulator‐based DEP (iDEP) technique . In addition, DC‐biased AC electric fields have been increasingly used to control the motion of particles in microchannels.…”

“…Both the DC and AC voltages are applied through electrodes (e.g., platinum wires) that are positioned into the channel‐end reservoirs for concurrent DC electrokinetic transport of the particulate solution and DC/AC dielectrophoretic manipulation of the suspended particles . This approach thus combines the advantages of DC and AC electrokinetics and offers independent controls of DC electrokinetic and AC dielectrophoretic motions .…”

“…Three types of nonlinear electrokinetic phenomena are typically involved in DC electrokinetic manipulation of particles in microchannels, which are dielectrophoretic particle motion, electrothermal fluid flow, and induced charge electroosmotic fluid flow . These phenomena are briefly reviewed below with the focus on particle DEP because the two fluid flows are usually rendered weak in electrokinetic microfluidic devices in order to minimize the adverse impacts on the samples and devices and as well ensure the accuracy in particle transport and placement . The review of the recent studies on nonlinear fluid flows in electric field‐mediated microfluidic devices will be deferred to a future article.…”

“…In contrast, iDEP microdevices utilize in‐channel insulating microstructures to block electric current for the generation of locally nonuniform electric fields . Both DC and DC‐biased AC electric fields can be used in iDEP devices . Depending on if they are more or less polarizable than the suspending fluid, particles migrate either along (i.e., positive DEP or pDEP) or against (i.e., negative DEP or nDEP) the electric field gradients with a dielectrophoretic velocity, , which, for spherical particles under the point‐dipole approximation , is given by: where denotes the real part of the complex Clausius−Mossotti (CM) factor, and are the complex permittivity of the particle and fluid, respectively, with being the particle permittivity, the particle conductivity, , ω the angular frequency of the electric field, and σ the fluid conductivity.…”

Joule heating effects in optimized insulator‐based dielectrophoretic devices: An interplay between post geometry and temperature rise

“…Nonetheless, due to the electric charges present in the channel and particles surfaces, and to ions in solution, electrophoresis (EP) and electroosmosis (EO) compete with DEP in controlling particle motion . This, in addition to the long distance between electrodes in iDEP‐based devices (∼10 −2 m), significantly increases the stimulation voltage requirements for the device, reaching values in the 10 2 –10 3 V range .…”