| Summary: | 碩士 === 國立清華大學 === 動力機械工程學系 === 102 === The oviduct is imitated with a biochip system for microfluidic dielectrophoresis (DEP). We show the trapping of an ICR mouse oocyte using the insulator structure of the microchannel in our dielectrophoresis system. To decrease the impact and destruction of the oocyte and the sperm, we adopted a positive dielectrophoretic force to manipulate the oocyte. To imitate a fertilization in vitro (IVF), the oocyte became positioned through the DEP force in the microfluidic channel; then we trapped many more sperm near the oocyte with a positive dielectrophoretic force to enhance the probability of natural fertilization. The oocyte was hence able to become positioned in the micro-channel. At the same time, the sperm swam in the same direction so that many more sperm were trapped near the oocyte to enhance the probability of natural fertilization. Primarily through a non-uniform electric field, the dielectrophoretic force induced the distribution of the electric field.
According to the differences between the relative permittivity and conductivity of the particle and solutions, a difference of dipole moment formed in the electric field. With varied polarization characteristics of the ability of the particles and the buffer solution to generate the positive or negative dielectrophoresis effect, the particles were affected by the DEP force to move to the region with a large or small density of electric field to achieve the goal of oocyte positioning. The positive dielectrophoretic response of an oocyte was exhibited with applied voltage 10 Vpp and frequency 1 MHz; the oocyte was affected by the positive DEP force to move to the region with a large density of electric field. To understand where the positions with a large and small distribution of the electric field in the microchannel, we used commercial numerical software (CFDRC-ACE+) to calculate the location of a large electric field. The pattern of the insulating structure was fabricated with SU8-3050 to generate a non-uniform electric field to trap the oocyte with positive dielectrophoresis. The result of our experiment indicated that a positive DEP served to drive the position of the oocyte and the sperm and to natural fertilization. This DEP microfluidic chip could improve the fertility rate from 14.2±7.5 % to 17.2±7.5 % at the low total sperm number.
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