An Insulating Constriction Dielectrophoresis Based Microfluidic Device for Protein Biomolecules Concentration

Sample enrichment or molecules concentration has been considered as an essential step for sample processing and biomarker detection recently in many applications involving miniaturized devices aiming at biosensing and bioanalysis, including the development of specialized tests for the detection of specific proteins and antibodies in human blood with the help of microfluidic and lab-on-a-chip devices. Among all the means involved to achieve this aim, dielectrophoresis (DEP) is increasingly employed in molecule manipulation and concentration because it is non-destructive and ensures high efficiency. However, there are still constraints on implementing the required functions using the dielectrophoresis technique in the devised micro-scale structures with high throughput, as well as the technical challenge in integration of sensors and concentration units for low-abundance molecular detection.;In the present work, we demonstrated a methodology to achieve protein concentration utilizing the combination effects of electrokinetics and low frequency insulator-based dielectrophoresis (iDEP) generated within a microfluidic device, in which a submicron constricted channel was fabricated using DNA molecular combing and replica molding. This fabrication technique, avoids using e-beam lithography or other complicated nanochannel fabrication methods, provides an easy and low cost approach with the flexibility in controlling channel dimensions to create highly constricted channels embedded in a microfluidic device. With theoretical analysis and experiments, we demonstrated that albumin--fluorescein isothiocyanate conjugate (FITC-BSA) protein molecules can be significantly concentrated to form an arc-shaped band near the constricted channel under the effects of negative dielectrophoretic force and DC electrokinetic forces within 2-3 minutes. It was also observed that the amplitudes of the applied DC and AC electric fields, AC frequencies, as well as suspending medium conductivities had strong effects on the concentration responses of the FITC-BSA molecules, including the concentrated area and position, intensities of the focused molecules, and concentration speed.;Our method demonstrated in the thesis provides a simple and flexible approach for quickly concentrating protein molecules by controlling the applied electric field parameters. The iDEP device reported in this thesis can be used as a stand-alone sensor or worked as a pre-concentration module integrated with biosensors for protein biomarker detections. Furthermore, low frequency dielectrophoresis provides practical uses for integrating the concentration module with a portable biosensing system