Assessment of Sub-Micron Particles by Exploiting Charge Differences with Dielectrophoresis

Abstract

The analysis, separation, and enrichment of submicron particles are critical steps in many applications, ranging from bio-sensing to disease diagnostics. Microfluidic electrokinetic techniques, such as dielectrophoresis (DEP) have proved to be excellent platforms for assessment of submicron particles. DEP is the motion of polarizable particles under the presence of a non-uniform electric field. In this work, the polarization and dielectrophoretic behavior of polystyrene particles with diameters ranging for 100 nm to 1 μm were studied employing microchannels for insulator based DEP (iDEP) and low frequency (<1000 Hz) AC and DC electric potentials. In particular, the effects of particle surface charge, in terms of magnitude and type of functionalization, were examined. It was found that the magnitude of particle surface charge has a significant impact on the polarization and dielectrophoretic response of the particles, allowing for successful particle assessment. Traditionally, charge differences are exploited employing electrophoretic techniques and particle separation is achieved by differential migration. The present study demonstrates that differences in the particle’s surface charge can also be exploited by means of iDEP; and that distinct types of nanoparticles can be identified by their polarization and dielectrophoretic behavior. These findings open the possibility for iDEP to be employed as a technique for the analysis of submicron biological particles, where subtle differences in surface charge could allow for rapid particle identification and separation.

Simple Approach to Reducing Particle Trapping Voltage in Insulator-Based Dielectrophoretic Systems

“…These results are as expected considering the modeling and experimental results obtained with 1 μm particles (Figure 3). Furthermore, the decrease in voltage requirements is considerable when compared to similar reported systems where nanoparticle trapping occurred at ∼3000 V. 31,34 Particle trapping in Figure 4a was achieved employing only 20% of the voltage used in similar systems. 31,34 The fluorescence analysis in Figure 4e clearly demonstrates that the design with only one column of posts has better performance in terms of particle trapping than the other three designs for the entire range of applied voltages studied.…”

“…Four distinct microchannel designs were employed in this study (Figure S1). Devices were fabricated in PDMS using conventional soft-lithography procedures listed in previous reports by our group. , The final dimensions of the fabricated devices are as mentioned in the Theory and Computational Model Section.…”

Fine-Tuning Electrokinetic Injections Considering Nonlinear Electrokinetic Effects in Insulator-Based Devices

“…Particle streaming is particle migration primarily under linear EK effects, and particle trapping is when particle migration is stalled by nonlinear EK effects and bands of trapped particles are formed leading to significant enrichment [24]. The potential of iEK systems is significant, as their applicability for separating and analyzing valuable particles, including protein particles [25], nanovesicles [26], viruses [27], cells [8,28,29], and micro and nanoparticles [30,31], has been fully demonstrated. Given this new knowledge, the present study was focused on designing EK sample injection schemes for DC-iEK systems while considering the effects of nonlinear EP (known as the EP of the second kind or EP (3) ).…”

Analytical Guidelines for Designing Curvature-Induced Dielectrophoretic Particle Manipulation Systems

“…where E is the externally applied electric field, f is the frequency of the applied voltage and f CM is the Clausius-Mossotti factor of the particle-fluid system. Based on the method of inducing electrical energy gradients, i.e., ∇(E•E), dielectrophoretic concentration process can be broadly classified as electrode-based (i.e., eDEP, where the gradients are generated by a set of patterned [22][23][24][25][26][27][28] or virtual electrodes [29]), insulator-based (i.e., iDEP, where the gradients are generated by non-uniform cross sections within the microfluidic circuit [30][31][32][33][34][35]), or curvature-induced (i.e., C-iDEP, where the curvature of the microfluidic channel produces unequal electric field intensities across a channel cross section [36]). Simply making the channel curved is sufficient to generate DEP, and hence, the cross section of the microfluidic channel need not be reduced, thereby rendering C-iDEP systems much less susceptible to localised Joule heating effects that are more prevalent in their insulator-based counterparts [37][38][39][40].…”