Research On Microfluidic Particle Detection And Counting System Based On Coulter Principle

The detection and counting of particles is widely used in various fields.The optical particle detection method is rich in information and the results are accurate.However,it costs much time to analyze the data by using the optical particle detection method,and the detection equipment,which must be used in special laboratory or environment,are expensive.In contrast,the electrical particles detection and counting method is more cost-effective.The resistance pulse sensing method,one branch of electrical particles detection and counting method has attracted much attention because its principle is simple,clear and the equipment required is cheap,small-scale and easy to integrate.In order to make a low-cost,portable,easy to integrate,and reliable particle resistance pulse detection system,the following are studied in this article:(1)Based on theoretical calculations,a microfluidic Coulter counting chip design that improves detection sensitivity and the electrodes are close to the detection area is proposed,the PDMS chip is prepared and the detection electrodes are integrated based on the principle of capillary valve.After comparing the physical and chemical properties and microelectrode fabrication performance of bismuth-indium-tin alloy,graphene,carbon nanotubes and conductive silver paste,the bismuth-indium-tin alloy was selected to integrate a precisely positioned detection electrode in the chip.(2)Based on the equivalent circuit of the detection chip,the source of the pulse signal in the resistance pulse particle detection is analyzed,and a noise reduction circuit with amplifier that can improve the detection sensitivity is designed and manufactured according to the signal characteristics.A high-resolution,portable,low-cost pressure injection system that can be controlled by mobile phone’s Bluetooth is designed and manufactured according to requirements.We selected a data acquisition module that meets the experimental requirements,and integrated it with a microfluidic detection chip,a noise reduction circuit with amplifier,and a pressure sampling system into a microfluidic resistance pulse particle detection system.According to the characteristics of the detection data,design a data processing and automatic counting algorithm.(3)The integrated microfluidic resistance pulse particle detection system was used to detect and count particles such as polystyrene microspheres,C.elegans and worm eggs.Taking the results of polystyrene microsphere detection and counting as an example,the causes and the characteristics of voltage pulse peak are analyzed.The detection results of platinum electrode and bismuth indium tin alloy electrode are compared,and the conclusion that the detection electrode closer to the detection area can improve the detection sensitivity is verified.The situation and results of detecting and counting C.elegans and worm eggs were compared and analyzed.By improving the chip structure design and detection parameters,the number of C.elegans and worm eggs was counted,which showed the application prospect of the research on reproductive toxicity of C.elegans.