Microfluidic diode pumping (part I) and rapid detection of stem cell differentiation using indium tin oxide Opto-electric Sensing (part II)

The thesis is separated into two topics: (I). Microfluidic diode pumping and (II). Rapid detection of stem cell differentiation using Indium Tin Oxide Opto-electric Sensing.;Part-I: Microfluidic diode pumping.;Fluid transfer is a frequently used function of microfluidic systems. Electroosmotic micropump (EOF) is one of the most common tools. However, the characteristics of the electroosmotic micropump (EOP) have not been fully discovered. Part I includes three different topics. The research involves a biological application, characteristic of the diode pump, and development of the AC-diode hybrid electroosmotic micropump.;(1). Dynamic microfluidic cell culture platform: The research explores an electroosmotic diode pump for a biological application of the dynamic cell culture platform. Many species of cells require ultra-low volumetric flow rate environments. The ultra-low EOF is applied by a surface mount diode in this research. The flow rates are controlled between 2.0 ∼ 12.3 nL/s in a high salt concentration (> 10 mM) aqueous solution. The A549 human lung cancer cells are cultured for a biocompatibility experiment under the ultra-low volumetric flow rate environment.;(2). Effect of diode connection and electrode location on diode pumping volume flow rates: Many characteristics of the diode pump still lack information. The research describes a method to increase volume flow rates and prevent the chemical electrolysis in the diode pump. First, the diodes, which are connected in parallel and series, are examined. A capacity of surface charges can be increased by connecting diodes. The volume flow rates of EOF are controlled by the capacity. The volume flow rate increases from 2.22 ∼ 7.6 nL/min at 10 Vpp with increasing diodes from 1 ∼ 3 when the diodes are connected in parallel. While the diodes are connected in series from 1 ∼ 3, the volume flow rate increases from 2.22 ∼ 3.34 nL/min. A direction reverse EOF is found. The reverse EOF is generated on PDMS surface, which seems resistant to the diode EOF. According to our mathematics model, it is not very efficient to increase the volume flow by connecting the diodes in series. However, the volume flow rates still can be efficiently controlled if the connection methods can be designed precisely. These results provide the significant insights to design the diode pump.;(3). Hybrid electroosmotic microfluidic pumping system: The purpose of research is to solve the disadvantage of the AC electroosmosis pump (EOP). An AC-DC electroosmotic pump is developed to solve the disadvantage of the ACEOP. AC EOP provides high flow rates and longer operating time solutions for the microchannel. However, the disadvantage of AC electroosmotic pump is direction change. The AC-DC EOP is a hybrid of alternating current (AC) and diode EOPs. The electrode patterns of the AC-DC EOP are symmetrically designed to avoid unwanted ACEOF generation. The flow rate of the AC is from 14 microm/min ∼ 144 microm/min for the input range of 0 ∼ 10 V pp and the Diode EOP is from 0 microm/min ∼ 95 microm/min. The response time to change flow directions is almost instantaneous. This hybrid system seems very useful for a microfluidic environment requiring both constant flow in one direction and rapid flow direction change in short periods of time such as sample resuspension.;Part-II: Rapid detection of stem cell differentiation using Indium Tin Oxide opto-electric sensing.;An Indium Tin Oxide opto-electric cellular sensing system (ITO-ECIS) is developed. The purpose of the developed system is to evaluate and detect the mesenchymal stem cells (MSCs) while MSCs are differentiating into osteoblast lineage. The conventional in-situ photochemstry methods can be retained at the end of the differentiation. The hMSCs and H9MSCs are two similar MSCs. Both of H9MSCs and hMSCs have similar differentiation response while treating with the same concentration induction media. The developed ITO-ECIS allows us to simultaneously record the differences of the impedance and images during the differentiation. During the differentiation, the resistance of the H9MSCs increases from 7 ∼ 32 % in 0.2 hours and hMSCs increases from 0 ∼ 17 % in 1 hour. In order to compare the impedance between H9MSCs and hMSCs, the reference impedance is selected on confluence cultured hMSCs before osteoblast induction. The results show that the H9MSCs obtain faster and stronger attachment response and calcium secretion than hMSCs. The stemness of the H9MSCs are better than hMSCs. The developed ITO-ECIS can be used to detect the stem cell differentiation in an early stage and classify the stemness between similar cells.