Paul V. Jones

Dielectrophoretic mobility determination in DC insulator-based dielectrophoresis

Insulator‐based dielectrophoresis (iDEP) is a powerful tool for separating and characterizing particles, yet it is limited by a lack of quantitative characterizations. Here, this limitation is addressed by employing a method capable of quantifying the DEP mobility of particles. Using streak‐based velocimetry the particle properties are deduced from their motion in a microfluidic channel with a constant electric field gradient. From this approach, the DEP mobility of 1 μm polystyrene particles was found to be −2±0.4 10−8 cm4/(V2 s). In the future, such quantitative treatment will allow for the elucidation of unique insights and rational design of devices.

Manipulation and capture of Aβ amyloid fibrils and monomers by DC insulator gradient dielectrophoresis (DC-iGDEP)

Here we report a novel method for the manipulation and concentration of Aβ amyloid fibrils, implicated in Alzheimers disease, using DC insulating gradient dielectrophoresis (DC-iGDEP). Fibril enrichment was found to be ∼400%. Simulations suggest that capture of the full range of amyloid protein aggregates is possible with optimized device design.

Continuous Separation of DNA Molecules by Size Using Insulator-Based Dielectrophoresis

Separation of nucleic acids has long served as a central goal of analytical research. Innovations in this field may soon enable the development of rapid, on-site sequencing devices that significantly improve both the availability and accuracy of detailed bioinformatics. However, achieving efficient continuous-flow operation and size-based fractionation of DNA still presents considerable challenges. Current methods have not yet satisfied the need for rapid fractionation of size-heterogeneous nucleic acid samples into specific and narrow size distributions. Dielectrophoretic (DEP) mechanisms integrated in microfluidic devices offer unique advantages for such applications, including short processing times, microscale reaction volumes, and the potential for low cost and portability. To facilitate such developments, we have adapted a microfluidic constriction sorter device to separate a wide range of nucleic acid analytes into distinct microchannel outlets. This work demonstrates selective and tunable deflection of DNA using alternating current (AC) insulator-based dielectrophoresis. We report conditions for size-based DEP sorting of 1.0, 10.2, 19.5, and 48.5 kbp dsDNA analytes, including both plasmid and genomic DNA. Applied potentials range from 200 to 2400 Vpp with frequencies ranging from 50 Hz to 20 kHz. These conditions result in sorting efficiencies up to 92% with a strong dependence on applied potentials and frequencies. In low-frequency AC fields, long DNA molecules form macro-ion clusters. This behavior is associated with an apparent shift from positive to negative DEP sorting behavior. Using a finite element model, we characterize the dynamics of sorting in the microdevice and link differential sorting to differences in dielectrophoretic mobility. We propose the use of a continuous-flow sorting strategy to facilitate future coupling to next generation sequencing approaches.

Development of the resolution theory for gradient insulator‐based dielectrophoresis

New and important separations capabilities are being enabled by utilizing other electric field‐induced forces besides electrophoresis, among these is dielectrophoresis. Recent works have used experimentally simple insulator‐based systems that induce field gradients creating dielectrophoretic force in useful formats. Among these, juxtaposing forces can generate gradient‐based steady‐state separations schemes globally similar to isoelectric focusing. The system of interest is termed gradient insulator‐based dielectrophoresis and can create extremely high resolution steady‐state separations for particles four nanometers to ten micrometers in diameter, including nearly all important bioparticles (large proteins, protein aggregates, polynucleotides viruses, organelles, cells, bacteria, etc.). A theoretical underpinning is developed here to understand the relationship between experimental parameters and resolution and to identify the best expected resolution possible. According to the results, differences in particles (and bioparticles) as small as one part in 104 for diameter (subnanometer resolution for a one micrometer particle), one part in 108 for dielectrophoretic parameters (dielectrophoretic mobility, Clausius–Mossotti factor), and one part in 105 for electrophoretic mobility can be resolved. These figures of merit are generally better than any competing technique, in some cases by orders of magnitude. This performance is enabled by very strong focusing forces associated with localized gradients.

Spatio-temporal image analysis of particle streaks in micro-channels for low-cost electro-hydrodynamic flow characterization

Flow characterization is a primary analytical method for performance evaluation of microfluidic devices. With the increasing prevalence of microfluidic devices in recent years, there is a growing need for simple methods of automated flow estimation. In this work, a novel flow diagnostic technique based on image analysis of particle streaks is introduced, to characterize local flow velocities. While 1D velocimetry using particle tracks has occasionally been discussed for macro-scale environments, the use of particle streaks for 2-D flow characterization in micro-channels has not been explored. The proposed technique is qualitatively validated against electroki-netic experiment and numerically validated with simulated flows.