| The detection and sorting of particles or cells is of great value in many biomedical researches,and technologies to separate biological particles into homogeneous populations have been intensively studied in recent years.However,many current particle sorting methods require the target object to be labeled first,which increases the complexity of the experiment and may affect the activity of biological objects.Microfluidic electrical impedance detection technology has developed into a very promising method in the detection of tiny particles due to its advantages of label-free,real-time,and high-throughput.However,in the current research on sorting technology based on electrical impedance detection,there is a lack of detailed analysis of the location of the particles in the microchannel when the sorting is triggered,resulting in no good matching between the detection and the sorting action.In this paper,the electrical impedance detection technology and piezoelectric sorting technology are combined.Through the real-time acquisition and processing of electrical impedance data,the detection and sorting actions are well matched,and the label-free detection and high-purity sorting of polystyrene beads of different sizes are realized.This microfluidic sorting technology based on electrical impedance detection can be used for label-free sorting of cells,and has broad application prospects in single-cell detection and single-cell omics research.The main work of this paper as follows:(1)Principle research and signal characteristic analysis of microfluidic electrical impedance detection technology.The working principle of electrical impedance detection technology is studied and the corresponding equivalent circuit model is established.The finite element method is used to simulate the electrical impedance detection process of particles,which lays a theoretical foundation for subsequent experiments.For the electrical impedance detection experiments of 10 μm and 7 μm mixed polystyrene beads,the peak amplitude of the particles can be used as a reliable indicator to distinguish between the two types of particles by analyzing the signal characteristics.However,due to the difference in size and shape of HeLa cells,the peak amplitude of the signal has a larger coefficient of variation than that of particles.(2)Research on real-time acquisition and processing of electrical impedance data.In order to achieve a good cooperation between electrical impedance detection and downstream piezoelectric sorting,a custom program written in MATLAB is used to acquire and analyze electrical impedance data in real time.Through the reasonable calculation of various times during the operation of the system,the position of the particles in the microchannel at the moment of triggering the sorting is accurately predicted,which is crucial for subsequent sorting,and the error in particle position prediction is analyzed.(3)Research on particle sorting technology based on electrical impedance detection.A piezoelectric sorting scheme based on electrical impedance detection is proposed,and the structural composition and manufacturing process of the microfluidic chip are studied.The chip mainly consists of two parts,the microchannel and the electrode.Based on this,an experimental platform for particle sorting based on electrical impedance detection is built.After research,the trigger area obtained by the electrical impedance detection to predict the particle position is all in the appropriate piezoelectric sorting area,which confirms the feasibility of combining electrical impedance detection and piezoelectric sorting to achieve particle sorting.For the sorting of 10 μm and 7 μm mixed polystyrene beads solution,the sorting purity of 10μm particles is 94.9%and the throughput is 1.6 Hz. |
