The field of sample enrichment is currently receiving a large amount of attention because it is essential to reduce the time required for many laboratory processes. Dielectrophoresis, or the motion of a polarized particle in the presence of a non-uniform electric field, has emerged as a promising method for biological sample concentration. By relying upon electrical properties that are intrinsic to a cell or microparticle, dielectrophoretic concentration avoids the need for sample preparation procedures which can greatly reduce the throughput of a system. Contactless Dielectrophoresis (cDEP) is a promising manifestation of dielectrophoresis in which the electrode structures that provide the non-uniform electric field are physically separated from the sample by a thin dielectric barrier. This work presents two methods for providing the high-voltage and high-frequency signal necessary to generate a non-uniform electric field in the sample channel of a cDEP device. The first method, an oscillator-based system, was able to produce DEP trapping and pearl-chaining of THP-1 and MCF-7 breast cancer cells in a cDEP device. The second method presented here utilizes an amplifier and transformer combination to generate very high voltages over a wide range of frequencies. Finally, electrorotation, or the spin imparted to a particle due to a rotating electric field has proven to be an extremely useful analysis of a cell's dielectric properties. A wideband, computer controlled function generator, outputting four sinusoidal waveforms in quadrature is presented. This device was able to produce outputs with the proper alignment over the range of 10 Hz to 100MHz. / Master of Science

A method for the selective concentrating of DNA targets using capillary affinity gel electrophoresis is presented. Complementary ssDNA targets are retained through hybridization with oligonucleotide probes immobilized within polyacrylamide gels while non-complementary targets are removed. The captured DNA targets were concentrated by step elution, where a localized thermal zone was applied in small steps along the capillary. Evaluation of the selective capture of a 150 nt DNA target in a complicated mixture was carried out by factorial analysis. Gels with a smaller average pore size were found to retain a higher amount of complementary targets. This was thought to be due to the ssDNA target migrating through the gel by reptation, eliminating hairpin structures, making the complementary region of the target available for hybridization. This method was applied to a series of DNA targets of different lengths, 19 nt, 150 nt, 250 nt and 400 nt. The recovery of the method ranged from 0.5 to 4% for the PCR targets, and 13 to 18% for the 19 nt oligonucleotide target. The purity was calculated to be up to 44% for the PCR targets and up to 86% for the 19 nt target. This was an improvement in purity of up to 15 times and 1100 times in comparison to the original samples for the PCR targets and 19 nt oligonucleotide, respectively. The 19 nt targets were selective concentrated and delivered into a microfluidic based DNA biosensing platform. The purity of the sample improved from 0.01% to 50% while recovery decreased from 100% to 20% for a sample with 0.5 nM complementary and 1 μM non-complementary targets. An improvement in the response of the sensing platform was demonstrated on 19 nt oligonucleotide targets delivered by selective concentration versus concentration alone into the microfluidic biosensing system.

A method for the selective concentrating of DNA targets using capillary affinity gel electrophoresis is presented. Complementary ssDNA targets are retained through hybridization with oligonucleotide probes immobilized within polyacrylamide gels while non-complementary targets are removed. The captured DNA targets were concentrated by step elution, where a localized thermal zone was applied in small steps along the capillary. Evaluation of the selective capture of a 150 nt DNA target in a complicated mixture was carried out by factorial analysis. Gels with a smaller average pore size were found to retain a higher amount of complementary targets. This was thought to be due to the ssDNA target migrating through the gel by reptation, eliminating hairpin structures, making the complementary region of the target available for hybridization. This method was applied to a series of DNA targets of different lengths, 19 nt, 150 nt, 250 nt and 400 nt. The recovery of the method ranged from 0.5 to 4% for the PCR targets, and 13 to 18% for the 19 nt oligonucleotide target. The purity was calculated to be up to 44% for the PCR targets and up to 86% for the 19 nt target. This was an improvement in purity of up to 15 times and 1100 times in comparison to the original samples for the PCR targets and 19 nt oligonucleotide, respectively. The 19 nt targets were selective concentrated and delivered into a microfluidic based DNA biosensing platform. The purity of the sample improved from 0.01% to 50% while recovery decreased from 100% to 20% for a sample with 0.5 nM complementary and 1 μM non-complementary targets. An improvement in the response of the sensing platform was demonstrated on 19 nt oligonucleotide targets delivered by selective concentration versus concentration alone into the microfluidic biosensing system.

Dielectrophoresis (DEP), an electrokinetic force, is the motion of a polarizable particle in a non-uniform electric field. Contactless DEP (cDEP) is a recently developed cell sorting and isolation technique that uses the DEP force by capacitavely coupling the electrodes across the channel. The cDEP platform sorts cells based on intrinsic biophysical properties, is inexpensive, maintains a sterile environment by using disposable chips, is a rapid process with minimal sample preparation, and allows for immediate downstream recovery. This platform is highly competitive compared to other cell sorting techniques and is one of the only platforms to sort cells based on phenotype, allowing for the isolation of unique cell populations not possible in other systems. The original purpose of this work was to determine differences in the bioelectrical fingerprint between several critical cancer types. Results demonstrate a difference between Tumor Initiating Cells, Multiple Drug Resistant Cells, and their bulk populations for experiments conducted on three prostate cancer cell lines and treated and untreated MOSE cells. However, three significant issues confounded these experiments and challenged the use of the cDEP platform. The purpose of this work then became the development of solutions to these barriers and presenting a more commercializable cDEP platform. An improved analysis script was first developed that performs whole cell detection and cell tracking with an accuracy of 93.5%. Second, a loading system for doing smart sample handling, specifically cell focusing, was developed using a new in-house system and validated. Experimental results validated the model and showed that cells were successfully focused into a tight band in the middle of the channel. Finally, a proof of concept for an on-chip micropump is presented and achieved 4.5% in-plane deformation. When bonded over a microchannel, fluid flow was induced and measured. These solutions present a stronger, more versatile cDEP platform and make for a more competitive commercial product. However, these solutions are not just limited to the cDEP platform and may be applicable to multitudes of other microfluidic devices and applications. / Master of Science