Microfluidic based impedance flow cytometry-dual microneedles for red blood cell detection

Abstract

This thesis presents a microfluidic impedance flow cytometry-dual microneedle device for cell detection. Single-cell detection plays a significant role in biomedical diagnostics, such as early cancer cell detection and pathogenic bacteria cells in the blood. The growing need for simple and low-cost microfluidic device fabrication led to the invention of numerous microfluidic-based impedance flow cytometry (IFC) techniques. The current method for impedance flow cytometry technique is limited to an expensive and complex fabrication process of gold microelectrode. Therefore, the IFC-dual microneedle device with a simple design structure and uncomplicated fabrication process for cell detection is presented. The device utilized the two Tungsten microneedles with 25 |im of tip diameter, placed at the half-height of the microchannel as the measurement electrode. The design was characterized and optimized in terms of physical dimension, leakage conditions and sensitivity. The polystyrene (PS) microbeads with three different sizes (5 |im, 7 |im and 10 |im), yeast cells with different concentrations and red blood cells (RBC) were utilized to perform the cell detection of this IFC device. This IFC device was able to detect as low as 1 .2 x 1 04 cfu/mL cells of yeast cells in a solution medium. Moreover, the ratio of the impedance at high frequency vs. low frequency, known as opacity, was used to discriminate between the PS microbeads and RBC. In addition, the proposed device demonstrated that the specific membrane capacitance of an RBC is 9.42 mF/m- , with the regression coefficients, p at 0.9895. Measured results were found to lie in the comparable range with the previous technique (7-14.3 mF/m ). The presented IFC-dual microneedle device provides an opportunity for simple medical and food safety screening processes in developing countries.