Research Of Cells' Distribution Visible Detection In Microchannel By Micro Electrical Impedance Spectroscopic Tomography

Micro elelctrical impedance spectroscopic tomography(?EIST)is developed to detect the separation process of abnormal cells(such as dead cells or cancer cells)visually in a microfluidic chip(Lab on a chip)for real-time monitoring.The purpose of the study is to develop a ?EIST system that visualy detects variety kinds of cells' distributions in microchannel.The objects of this study are living and dead yeast cell solution,the living yeast cells are represented as normal cells and the dead cells are abnormal cells.For the purpose,the method of ?EIST is developed in three steps of technologies after the studies of the basic principles.They are micro elelctrical impedance tomography(?EIT),micro electrochemical impedance spectroscopy(?EIS)and ?EIST.The research includes:Firstly,the basic theories and principles is summarized.It is mainly about the characteristics of fluids in microchannel and impedance detection on microelectrodes.The research of the flow field shows that the fluids is a stable laminar in the microchannel,which is beneficial to the electrical impedance detection.In the aspect of microelectrode impedance detection,the characteristics of microelectrode and micro sensor are summarized by the existing theoretical knowledge,combined with the analysis and verification of simulation and experiment.In the results of study,the voltage drop near the electrode is very large while using the microelectrode for electrical impedance detecting.The influence by contact impedance of electrical double layer(EDL)in the interface between electrode and solution is very large while the current frequency is low.In the aspect of cell detection,the low-frequency electrical impedance of cell solution is covered by contact impedance on electrodes,it reveals the detection of electrical impedance of microelectrode in the low-frequency range is limited.Secondly,the ?EIT is investigated by the supports of basic theory,and the purpose is to achieve visual detection of single kind of cell's distribution in the microchannel.Beside of the development of hardware and sofeware in ?EIT,the algorithms of image reconstruction in EIT inverse problem are compared by simulation.The effect of the EDL contact impedance on ?EIT is analyzed by simulation,the results show that while the influence of the contact impedance is increased,the imaging quality is decreased.In addition,the distribution of yeast cells which are deposited at the bottom of the microchannel was visually detected by experiments,the result shows while frequency of current is increased,the influence of the contact impedance is decreased,and the image quality is increased.When the frequency continues to increase,the image quality is decreased due to the decrease of impedance.At last,the best image quality is reconstructed near f = 1 MHz.Thirdly,on the basis of ?EIT which is used to reconstruct the living yeast cells distributution in microchannel,the impedance of various kinds of cells in mixed solution are detected by ?EIS.The method is established by the impedance model of the cell solution,and then verified by the experiments.The results show that the impedance of the cell solution is decreased while the ion concentration is increased.Based on the results,a quantitative measurement method by ?EIS which detects the living yeast fraction in the mixed living and dead cell solution in the microchannel is realized.The results showed that the conductivity of living cells was less than cell culture medium because of the high resistance of cell membrane,and the conductivity of dead cells was the highest because of the rupture of cell membrane.This theory also provides a selection method and basis for various cells to find out the best imaging frequency for each kind of cells in ?EIST.Finally,based on ?EIT and ?EIS,?EIST which supports multi-frequencies detection is developed.?EIST adopts the best characteristic frequency to image the distribution of each kind of cells,and then selects the suitable parts by adjustment function.At last,the ?EIST image is synthesized by the normalized images of all kinds of cells' distribution.In this study,due to the experimental conditions,Simulation is employed to reconstruct the distribution of living and dead yeast cells in mixed cell solution after separation.The final simulation results show that the image quality of ?EIST is better than single frequency condition.