The Mechanism And Experiment Of Protein Electrokinetic Enrichment By Floating Electrode

The miniaturization and diversification of microfluidic technology enables the microfluidic system to ensure that trace reactants react under optimal conditions.In general,the protein sample has a small capacity and a low expression level.The traditional detection method is difficult to meet the requirements of a small amount of low concentration sample,and a microfluidic method for increasing the relative content of the protein is needed.Induced charge electroosmosis is a particle manipulation technique that is highly advantageous in particle aggregation.It occurs on the surface of an electrode that is not charged under an electrical signal,and can achieve particle aggregation of different scales.In this paper,the enrichment experiments of polystyrene particles are carried out on the basis of studying the characteristics of electro-osmotic flow characteristics,electronically controlled particle behavior and chip geometry of particle enrichment,and finally enrichment of proteins.Firstly,according to the research on particle aggregation method and protein enrichment,a particle aggregation method based on induced charge electroosmotic collection technology is proposed.The electrode system is laid along the channel direction.The direct current component of the electrical signal causes the particles to move in a direction,and the stable vortex trapping particles generated by the interaction of the AC and DC components achieve enrichment.Secondly,the microscopic process of electroosmotic flow is analyzed.The complex amplitude phasor is introduced to derive the slip velocity formula of the sinusoidal signal on the surface of the electrode.The boundary condition is used to simulate the steady flow field in the channel.Based on the analysis of the stable vortex in the dynamic and static flow field,the region where the particles may be enriched is predicted.Thirdly,the effects of the above flow field,electric field and other native physics on the particles are studied.The actual effect of each physical quantity is measured.The calculation results of flow field and electric field are used to couple the transfer field of diluted species to complete the numerical simulation of particle enrichment.The influence of the main geometric parameters of the experimental chip is analyzed in the numerical simulation.The overall structural scheme of the chip C-1(single suspension electrode)and C-3(three suspension electrodes)is given in combination with the processing technology.At the same time,the electronic control characteristics of particle enrichment are obtained through simulation,and the range of experimental parameters is preferred.The enrichment experiments of polystyrene nanoparticles on C-1 and C-3 obtained the highest 8-fold PS particle enrichment results in the high frequency band,and verified the feasibility and experimental parameters of the chip for subsequent protein experiments.Finally,the C-1 chip was used for static and dynamic experiments on the protein,and the C-3 chip was subjected to long-term stable enrichment in multiple regions.The static experiment confirmed the validity of the vortex-enriched protein and the feasibility of the electronically controlled protein.The protein was enriched at both ends of the electrode to induce charge electroosmotic vortex,and the enrichment effect was up to 4 times at low frequency.The dynamic experiment showed the high-efficiency enrichment result of the protein,and further studied the electronic control characteristics of the enriched chip.The enrichment effect was generally good,and the enrichment result was up to 30 times.The enrichment experiments of the C-3 chip demonstrate the superiority of the parallel multielectrode in protein enrichment efficiency and stability.The success of the protein enrichment experiment confirms the feasibility of induced charge electroosmosis technology in biomolecular enrichment,and has broad application prospects in biology and medicine.