Continuous‐Flow Nanoparticle Trapping Driven by Hybrid Electrokinetics in Microfluidics

Abstract

We introduce herein an efficient microfluidic approach for continuous transport and localized collection of nanoparticles via hybrid electrokinetics, which delicately combines linear and nonlinear electrokinetics driven by a composite DC‐biased AC voltage signal. The proposed technique utilizes a simple geometrical structure, in which one or a series of metal strips serving as floating electrode (FE) are attached to the substrate surface and arranged in parallel between a pair of coplanar driving electrodes (DE) in a straight microchannel. On application of a DC‐biased AC electric field across the channel, nanoparticles can be transported continuously by DC bulk electroosmotic flow, and then trapped selectively onto the metal strips due to AC‐field induced‐charge electrokinetic (ICEK) phenomenon, which behaves as counter‐rotating micro‐vortices around the ideally polarizable surfaces of FE. Finite‐element simulation is carried out by coupling the dual‐frequency electric field, flow field and sample mass transfer in sequence, for guiding a practical design of the microfluidic nanoparticle concentrator. With the optimal device geometry, the actual performance of the technique is investigated with respect to DC bias, AC voltage amplitude, and field frequency by using both latex nanospheres (∼500 nm) and BSA molecules (∼10 nm). Our experimental observation indicates nanoparticles are always enriched into a narrow bright band on the surface of each FE, and a horizontal concentration gradient even emerges in the presence of multiple metal strips, which therefore permits localized analyte enrichment. The proposed trapping method is supposed to guide an elaborate design of flexible electrokinetic frameworks embedding FE for continuous‐flow analyte manipulation in modern microfluidic systems.

Design and 3D modeling investigation of a microfluidic electrode array for electrical impedance measurement of single yeast cells

“…With the rapid development of microfabrication technologies, multiple essential components, such as microstructures, valves, and electrodes, have been miniatured to microscale dimensions and integrated into microfluidic devices for isolation and immobilization [8, 9], morphology‐ [10] or viability‐based [11, 12] sorting, as well as simultaneous culturing and imaging [13–15] of budding yeast cells. By implementing electrodes into microfluidic devices, precise manipulation of conducting fluid, droplets, or cells based on electrokinetics has also been reported, providing flexible methods to control continuous flows or particles in micro‐total‐analytical systems or single‐cell analysis [16–18]. Besides, in virtue of long‐term imaging, microchambers were used for lineage tracking of single budding yeast over several generations [19, 20].…”

Biological Characteristics of Cell Similarity Measure

“…These Raman and infrared spectra also have shown the rich basic data and intrinsic structural or biological characteristics of the analytical molecules, materials, proteins, cells, and tissues. Intelligent microsystem [ 24 ] has achieved great progress recently, which can well integrate these Raman and infrared technologies in it. Therefore, SWS would not only provide new thoughts and solutions in the similarity measure on the complex data characteristics of single‐cell Raman spectroscopy, but also inspire more practical applications in other Raman and infrared technologies.…”

AC electrokinetic isolation and detection of extracellular vesicles from dental pulp stem cells: Theoretical simulation incorporating fluid mechanics

“…Another AC electrohydrodynamic mechanism termed ACEO, which accounts for rotational fluid motion above electrode surface has been studied in literature to play a role in micro‐ and nanoparticle trapping when exposed to the low‐frequency nonuniform electric field [39–41]. The dependency of ACEO on AC field frequency can be explained by the tangential component of the force (, which is a function of built‐up charges on the electrode surface.…”