Research On Sorting And Detection Of Microalgae Cells Based On Microfluidic Chips

Microalgae is an important marine resource,which has wide application prospects in marine environment,biomedicine,bioenergy,food industry and many other fields.The separation and detection technology of microalgae cells is the key problems in the field of microalgae cell research.Traditional sorting and detection methods rely on the large-scale laboratory equipment,which is expensive,complex,time-consuming and labor-consuming.It is difficult to achieve rapid on-site sorting and detection.Therefore,the development of a small,fast,low-cost,easy to operate microalgae separation and detection technology has become a bottleneck problem restricting the research and utilization of microalgae resources.Microfluidic chip technology can achieve cell culture,control,analysis on the micron scale,is a ideal method for portable cell analysis and processing techniques.Therefore,this paper uses the microfluidic chip as the research platform to conduct in-depth researches on the key issues of microalgae cell sorting and detection technology.The main research contents are as follows:(1)According to the difference of microalgae cell size,a new method of microalgae cell separation based on deterministic lateral displacement was proposed.The effect of chip geometry parameters and flow rate on separation efficiency was analyzed,and the trajectory of microalgae cells under different conditions was studied.According to the flow field characteristics and the geometric parameters of chip,a separation chip system was designed and constructed,Pyramimonas Sp.and Chlorella were used as experimental samples to achieve the separation of different types of microalgae cells.(2)According to the difference of microalgae cell size and shape,a new microalgae cell separation method based on the principle of inertial force in a spiral microchannel was proposed.The factors affecting inertial migration of microalgae cells was analyzed.From the aspects of size and shape of microalgae cells and fluid flow velocity,the main factors affecting the microalgae cells' focus balance position in the microchannel were analyzed.The regularities of the influence of the shape characteristics of microalgae cells on the focus balance position was discovered,and a microfluidic inertial cell separation system was designed and constructed to achieve the separation of different microalgae cells.(3)According to the differences in the electrical characteristics of microalgae cells,a new method of microalgae cell separation based on the principle of dielectrophoresis was proposed.The relationship between the movement characteristics of microalgae cells and the dielectrophoretic force at different frequencies was analyzed,and the frequency response characteristics of microalgae cells were obtained.The effects of external electric field,flow rate,cell characteristics,etc.on the separation efficiency were studied.The microfluidic chip and the microalgae cell dielectrophoresis separation system were designed and constructed to separate different kinds of microalgae cells.(4)A new method for quickly obtaining the parameters of microalgae cell chemical inactivation based on the concentration gradient generation chip was proposed.Based on Hagen-Poiseuille's law and the principle of convective mass transfer,the relationship between the flow resistance of the microchannel and the geometric characteristics of the channel was analyzed.According to the principle of the equivalent circuit,a "Christmas tree"concentration gradient microfluidic chip was designed to quickly and accurately obtain the required concentration of chemical inactivation reagents.The treatment effect of microalgae cells at different chemical reagent concentrations was analyzed,thus,the parameters such as the optimal concentration of inactivation reagent can be obtained quickly.(5)A new method was proposed to detect the activity of microalgae based on the principle of lensless holographic imaging.The cell viability analysis was carried out through the microalgae cell hologram characteristics,and the relationship between the microalgae cell viability and the hologram characteristics(central bright spot,first dark stripe,first gray level difference,etc.)was studied and obtained.Analyzed the correlation between hologram characteristics and cell size,refractive index,membrane transmittance and other factors.A lensless holographic imaging system for microalgae cells was designed and constructed,and the effectiveness of the proposed method was verified by experiments.