Research Of Electric Detection And Dielectrophoresis Particle Separation Of Single Cell Organisms On A Microfluidic Chip

In order to monitor the dynamic change of the ecology and organisms and consequently analyze the number and sizes of the organisms within the polluted environment, it is very important for the development and application of microfluidic chip based portable devices which can not only detect, count and size the organisms but also can differentiate the pollutants and the target species.Based on the Coulter principle and by designing two detection channels, the working principle and factors influencing the signal magnitudes are theoretically analyzed and an equation to optimize the chip design was derived, by means of the equivalent electrical circuit theory.Afterwards, a submicron size sensing gate with the smallest width of0.74μm was soft-lithographically fabricated by asymmetrically designing the sensing gate. With this sensing gate,220nm particles were successfully detected with the help of the two-stage differential amplification detection system. The S/N is4-10.A method of calculating sample concentration by counting the number of particles per unit time was proposed and experimentally verified. The experimental results show the counted number rate per unit time is a linear function of the sample concentration in cells/mL with a correlation coefficient (R2) larger than0.99. Using this experimentally obtained correlation curve, the number of organisms in the sample can be rapidly determined within1-2minutes.Algae size distribution was rapidly determined on a microfluidic chip. Also, it was found that the shape and the rotation of particle can influence the shape of the RPS pulse, which can be employed to differentiate the spherical algae and the irregular Pseudokirchneriella subcapitata.The continual separation of Pseudokirchneriella subcapitata and Chlorella vulgar is, algae and5μm polymer particles were achieved by combining DC dielectrophoresis and electroosmotic flow. This method is simple and can be employed for sample pretreatment by non-professional people.A microfluidic chip integrated with functions of dielectrophoresis separation and electric detection was designed and employed for the sequencial separation of impurities from the algae sample and algae electric detection. The researches in this diesseration improved the understanding of the traditional Coulter principle and have some values for the development of fast analysis techonologies and microfluidic chip based portable devices for the single cell organism detection within complex samples.