A wide-bandwidth power amplifier for frequency-selective insulator-based dielectrophoresis

Farmehini, Vahid; Rohani, Ali Haeri; Su, Yi‐Hsuan

doi:10.1039/c4lc00801d

Cited by 28 publications

(27 citation statements)

References 19 publications

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“…With the aid of a step-up transformer or other equipment modifications as suggested in [152], higher voltages can be obtained without approaching the dielectric breakdown of fused silica (950 V/μm [153]) while maintaining a range of optimal and commonly used frequencies (1-1000 kHz [147]). Future work will make use of such equipment to demonstrate how fused silica can provide a higher range of applied voltage due to the dielectric breakdown.…”

Section: Discussionmentioning

confidence: 99%

The use of microfluidics and dielectrophoresis for separation, concentration, and identification of bacteria

et al. 2016

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Traditional bacterial analyses take one to two days under favorable conditions where the bulk of the time is spent waiting for bacteria to divide and grow until visual colonies can be observed for identification. In the case of bacteria with slow doubling times, this process can take weeks. This delay in analysis is unacceptable, especially in cases of life threatening diseases or emergencies. It is clear that in order to decrease the analysis time of the bacteria, the culturing and growth step must be circumvented. The goal of this research is to design, build, and test a device that could decrease the analysis time of bacteria using label-free methods of dielectrophoresis and Raman spectroscopy.Testing for device design was performed with clinical samples in mind, which consist of bacteria grown in a variety of environmental conditions (i.e. available food sources, growth stage, temperature, etc.) and accompanied by sample debris. Raman spectra of bacteria grown in varying media and metabolic stages were collected and analyzed. Results indicate that growth phase and media have an impact on Raman spectra iv and is distinguishable by linear discriminant analysis (LDA). Despite these spectral differences, it was found that LDA classification of closely related bacteria remains fairly high (90%) regardless of growth phase. Sample debris were also considered in device design and accommodated for by dielectrophoresis. Devices were built with the goal to isolate bacteria from a mixed sample and simultaneously acquire Raman spectra for identification.For this dissertation, a device was designed, built, and tested that incorporates dielectrophoresis for particle isolation and Raman spectroscopy for identification. The device was modeled in COMSOL to ensure that an appropriate electrical field gradient could be obtained to isolate bacteria from 5 µm diameter polystyrene spheres. The device was built and successfully trapped bacteria away from polystyrene spheres and Raman spectra of the bacteria were collected while trapped. These results indicate a clear potential for contactless dielectrophoresis-Raman devices to isolate and identify bacteria from sample debris, and thereby decrease the analysis time of bacteria. Typical bacterial analysis involves culturing and visualizing colonies on an array of agar plates. The growth patterns and colors among the array are used to identify the bacteria. For fast growing bacteria such as Escherichia coli, analysis will take one to two days. However, slow growing bacteria such as mycobacteria can take weeks to identify.In addition, there are some species of bacteria that are viable but nonculturable. This lengthy analysis time is unacceptable for life-threatening infections and emergency situations. It is clear that to decrease the analysis of the bacteria, the culturing and growth steps must be avoided. The goal of this research is to design, build, and test a device that could decrease the analysis time of bacteria.

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Section: Discussionmentioning

confidence: 99%

The use of microfluidics and dielectrophoresis for separation, concentration, and identification of bacteria

et al. 2016

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“…Details of experimental device geometry and operation are available in prior work 20,39,40 and in supplementary material S1. Alexa 488 labeled Streptavidin ($60 kDa) was procured from Molecular Probes (Eugene, OR).…”

Section: B Experimental Methodsmentioning

confidence: 99%

Nanoslit design for ion conductivity gradient enhanced dielectrophoresis for ultrafast biomarker enrichment in physiological media

et al. 2016

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Selective and rapid enrichment of biomolecules is of great interest for biomarker discovery, protein crystallization, and in biosensing for speeding assay kinetics and reducing signal interferences. The current state of the art is based on DC electrokinetics, wherein localized ion depletion at the microchannel to nanochannel interface is used to enhance electric fields, and the resulting biomarker electromigration is balanced against electro-osmosis in the microchannel to cause high degrees of biomarker enrichment. However, biomarker enrichment is not selective, and the levels fall off within physiological media of high conductivity, due to a reduction in ion concentration polarization and electro-osmosis effects. Herein, we present a methodology for coupling AC electrokinetics with ion concentration polarization effects in nanoslits under DC fields, for enabling ultrafast biomarker enrichment in physiological media. Using AC fields at the critical frequency necessary for negative dielectrophoresis of the biomarker of interest, along with a critical offset DC field to create proximal ion accumulation and depletion regions along the perm-selective region inside a nanoslit, we enhance the localized field and field gradient to enable biomarker enrichment over a wide spatial extent along the nanoslit length. While enrichment under DC electrokinetics relies solely on ion depletion to enhance fields, this AC electrokinetic mechanism utilizes ion depletion as well as ion accumulation regions to enhance the field and its gradient. Hence, biomarker enrichment continues to be substantial in spite of the steady drop in nanostructure perm-selectivity within physiological media. Published by AIP Publishing. [http://dx

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“…Device geometry for pre-concentration Dielectrophoresis was conducted within an electrode-less device geometry, with external Pt electrodes (Alfa Aesar) that were driven using a function generator (Agilent 33220 A) and a voltage amplifier 33 for generating applied fields of $300 V pp /cm over a 10 kHz to 5 MHz frequency range, with sharp dielectric constrictions to create localized high field points for enabling DEP pre-concentration of polarized particles at the constriction tips by pDEP or away from constriction tips by nDEP. In this manner, fluorescently labeled NPY biomarkers (Phoenix) were pre-concentrated in PBS media (150 mM NaCl and 2 mM NaN 3 ) at pH 7.2 and r m $ 1.6 S/m, using AC fields in the 1-3 MHz range within a quartz nanochannel (200 nm depth) away from constrictions (30 lm to 30 nm over 3 lm extent).…”

Section: Methodsmentioning

confidence: 99%

Quantifying spatio-temporal dynamics of biomarker pre-concentration and depletion in microfluidic systems by intensity threshold analysis

Rohani

Varhue

2014

Biomicrofluidics

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Microfluidic systems are commonly applied towards pre-concentration of biomarkers for enhancing detection sensitivity. Quantitative information on the spatial and temporal dynamics of pre-concentration, such as its position, extent, and time evolution are essential towards sensor design for coupling preconcentration to detection. Current quantification methodologies are based on the time evolution of fluorescence signals from biomarkers within a statically defined region of interest, which does not offer information on the spatial dynamics of pre-concentration and leads to significant errors when the pre-concentration zone is delocalized or exhibits wide variations in size, shape, and position over time under the force field. We present a dynamic methodology for quantifying the region of interest by using a statistical description of particle distribution across the device geometry to determine the intensity thresholds for particle pre-concentration. This method is applied to study the delocalized pre-concentration dynamics under an electrokinetic force balance driven by negative dielectrophoresis, for aligning the pre-concentration and detection regions of neuropeptide Y, and for quantifying the polarizability dispersion of silica nano-colloids with frequency of the force field. We envision the application of this automated methodology on data from 2D images and 3D Z-stacks for quantifying pre-concentration dynamics over delocalized regions as a function of the force field. V C 2014 AIP Publishing LLC.

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A wide-bandwidth power amplifier for frequency-selective insulator-based dielectrophoresis

Cited by 28 publications

References 19 publications

The use of microfluidics and dielectrophoresis for separation, concentration, and identification of bacteria

The use of microfluidics and dielectrophoresis for separation, concentration, and identification of bacteria

Nanoslit design for ion conductivity gradient enhanced dielectrophoresis for ultrafast biomarker enrichment in physiological media

Quantifying spatio-temporal dynamics of biomarker pre-concentration and depletion in microfluidic systems by intensity threshold analysis

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