Design Of Living Cell Concentration Detection System Based On Capacitance Method

Today,with great research progress in microbial science,both biopharmaceuticals and industrial fermentation are inseparable from the culture process of corresponding cells.In the process of cell culture,the identification of cell activity and live cell concentration information are key to our analysis and regulatory control of biological processes.How to understand and record the growth of cells in time while avoiding the pollution of the cell culture environment in the cell culture process has become an urgent problem to be solved by relevant researchers in China.Aiming to achieve a real-time,accurate and online measurement of the concentration of living cells,and by comparing other existing methods,a detection system for the concentration of living cells based on capacitance method is designed.By considering the living cells under a certain alternating electric field frequency as capacitors,an equivalent circuit model in the solution environment is established.To solve the problem that it is difficult to measure the tiny capacitance in the solution environment,the thesis adopts the method of partial pressure and uses the principle of equal impedance to calculate the relationship between the equivalent capacitance and the equivalent resistance in the solution,the method of two-phase lock-in amplification is adopted to measure the phase angle and obtain the voltage of the voltage dividing resistor,by which is bought into the calculation to obtain the equivalent capacitance and resistance value in the solution.STM32F4 is taken as the core control processor of the measurement system.By uploading the final measured data to the host computer through the corresponding circuit design and software logic control,the measurement results is displayed graphically and intuitively on the host computer interface.And the measurement mode can be set to control the work of the whole system in the benefits of the simple and friendly host computer interface.A system test platform is built to verify the system through actual measurements when the design is completed.The accuracy and stability of the system are first tested with standard capacitance and resistance.It is proved by experiments that the system can achieve highprecision measurement of capacitance and resistance within a certain range.The yeast cell aqueous solution was tested by sweep frequency and single frequency respectively,and the measurement data were analyzed.The results show that the measurement system has strong sensitivity and correlation to the concentration of living cells.