Microfluidic Driving And Mixing Based On AC Electrothermal And Its Biological Experiments

Culture cells or tissues and drug test in vitro is a key method of third-generation medical treatment, which solve medicinal development problems i.e. large cost and long period. Microfluidics with the advantages of low cost, fast response, high integration are suitable for the application of testing human cells or tissues in vitro. Organs-on-a-chip is a new and key application of microfluidics, which aims mimic the environment of human body by coupling multifarious organ chips. Pumping is a necessary condition of the organs-on-a-chip system. However, current pumping method couldnot meet the requirement of the organs-on-a-chip system. Therefore, this thesis focus on dynamic culture cells or tissues in vitro and the pumping method for organs-on-a-chip system.AC electrohydrodynamic micropumps control microfluidic by microelectrodes are desirable on-chip pumps. AC electrohydrodynamic micropumps include AC electroosmosis(ACEO) and AC electrothermal(ACET) mechanisms. Arising from the interaction of a tangential electric field and induced charge, ACEO is only effective for low conductivity fluids and thus, is unsuitable for human body fluids. However, ACET emerges from the interaction of an electric field and temperature gradient, and is especially suited for driving a wide range of high conductivity fluids. This thesis firstly researches the theory of ACET. An enhanced multi-physics coupling model was built to improve poorly predictive ACET classical model. The new equations of ACET body force were derivated, which lay the foundation for exact prediction of ACET effect.A multifunctional resealable perfusion bioreactor driven by syringe pump is designed and fabricated to research the differences of culture cells or tissues in a dynamic environment and conventional static method. The fluid in bioreactor supply a dynamic environment to mimic the the human environment for cell or ti ssue culture in vitro. Human embryonic kidney cells(HEK293T) and human colon carcinoma cells(SW620) were submerged cultured in the chip for 72 h. Cell viability and cell proliferation tests were used to evaluate the performance of the chip. Moreover, an artificial epidermis was developed, and it lasted for 7 days of submerged culture immortal human keratinocytes(Ha Ca T) monolayer and 35 days of air–liquid interface differentiated culture. The artificial epidermis cultured in the chip and in a conventional transwell was evaluated by the Live/Dead Viability/Cytotoxicity kit, histology, and hematoxylin & eosin staining. The stability and the benefits of our resealable chip were demonstrated by culture cells and epidermis tissue.To avoid the deleterious effects of Joule heating and electric current on sample cells, a rectangular microchannel was designed with distantly separated regions for pumping and cell culture. Temperature variations were examined using a commercial thermocouple sensor to detect temperature values in both pumping and culture regions. To generate a sufficient ACET circulatory pumping rate, 30 pairs of asymmetrical electrodes were employed in the pumping region, generated ACET velocity was measured by fluorescent microparticle image velocimetry. The benefits of our pumping chip were demonstrated by culturing human embryonic kidney cells(HEK293T) and human colon carcinoma cells(SW620) for 72 h with an energized voltage of 3 V and 10 MHz. Cells grew and proliferated well, implying our ACET circulatory pumping chip has great potential for cell culture and tissue engineering applications. Then, the electrodes in the chip was optimize. The shape of the microchannel was changed to reduce the fluid resistance. Finally, the anticancer drug(5-Fluorouracil) resistance tests of SW620 were set in the chip, and the drug resistance curve of SW620 cultured in the chip was created.To provide a mixer for organs-on-a-chip system, the conventional asymmetric electrodes were improved and new ACET mixing electrodes generated in-plane vortex were designed. By 3D simulation model, the mixing efficiency of many types of electrodes were evaluated. The simulated results were confirmed with the help of KCl solution with fluorescein. The benefits of our micromixer wit h electrodes rotating 60° were demonstrated by the drug(Tamoxifen) test of human breast cancer cells(MCF-7) for five days, which implies our ACET in-plane microvortices micromixer has great potential for the application of drug resistance of tumor cells in organ-on-a-chip systems.