Research On Mechanism Of No-Contact Microliquid Dispensing

With the development of biological analytical techniques and high throughput screening techniques, a large number of automated biological agents dispensing systems are widely used in the field of life science research. Non-contact dispensing method, characterized by its small dispensing volume, high dispensing precision and quick service speed,which satisfies the requirements of biological agents distribution, becomes the mainstream dispensing method used in reagent dispensing systems. However, the difficult control way, complex system of non-contact dispensing method,and it's vulnerable dispensing process, which can be easily affected by characteristics of the agent, have hindered the application and development of the method. In this paper, simulation model of the separation process of microscale biological reagent and equivalent model of the fluid pipeline of non-contact dispensing method are constructed in order to solve the above problems. The prerequisites of the non-contact dispensing method, the relationship between dispensing volume and precision and characteristics of reagents, formation of system and control parameters are researched through theoretical analysis and numerical simulations. Sequentially, theoretical guidance can be supplied for the design of the non-contact dispensing system and optimization of control method to ensure smaller volume reagents can be dispensed much faster with a higher accurate .First, based on CFD simulation software, Fluent, simulation model of the separation process of microscale biological reagent is constructed. The paper research the effects of characteristics of agent, dispensing volume, dispensing speed and size of nozzle on the separation process and precision of distribution, then showed the prerequisites of the realization of non-contact separation.Then, based on the analysis of the common characteristics of the existing non-contact liquid handling equipments, a typical dispensing system for non-contact dispensing method is designed. Equivalent model of this fluid system is constructed by lumped parameter method. Matlab simulation program map is constructed by using simulink subsystem functions. By modifying simulation parameters of the equivalent electrical components, the paper got the effect curves of the size of pipeline structure, driving pressure, air compression and working condition of solenoid valve on the dispensing process, and obtained the effect of system pressure, air volume and configuration of liquid system on the stability of the liquid velocity and the precision of dispensing volume. At last, the paper pointed out the direction of optimization of control parameters and the method for the realization of non-contact dispensing.Finally, an experimental platform based on the pressure-time drive for four non-contact dispensing channels is built. Based on the experimental platform, experiments of separation and precision of microscale agent distribution are conducted under different dispensing velocities and volumes with reagent of different viscosities and surface tensions. The good agreements between theoretical analysis and experimental results verify the reliability of the research achievements about the mechanism of non-contact dispensing.