Study On Characteristics Of A Microfluidic Close Loop Focusing System Based On Valveless Micropumps

The liquid optical system using liquid as working medium becomes a promising topic in the Microfluidic Technology. The liquid optical system which is made from certain liquid material can change the incident light routes by controlling the outline or the inner refractive index of liquid, to alter its focal length, to reflect the light and the other optical functions. Contrast with the traditional solid lenses, the liquid lenses have the advantages of more compact sizes, lower consumption of energy, more rapid response, wear- free and higher precision, hence they can be widely used in areas which need ultra compact dimensions and light weight. As a developing type of liquid lens, the Pressure-Controlled liquid lens needs accuracy controlled volume of working medium, which requires very high accuracy transducer. Most of the systems which are not available to those kind of transducers are open loop controlled systems.The close loop focusing system consists of the high accuracy laser displacement sensor as measure and feedback part, the valveless piezoelectric micropump as the key working parts, the PC, D/A output module and the piezoelectric ceramics driving power as the control parts is designed.The mathematical models of the valveless piezoelectric micropump and container holding the working medium, the mathematical principle of the finite element analysis are studied. The basic formulas of the micropump and the mathematical models between the film y axis displacement of the container and the volume variation of that are revealed. Then the finite element analyses of the piezoelectric vibrating film and the container are carried out, the relationship between the applied voltage and the vibrating film deformation, the relationship between the vibrating film deformation and the chamber volume variation, the relationship between container elastic diaphragm deformation and the volume variation are stated. The simulations of the single micropump, the double-pump system and the four-pump system which based on MATLAB/Simulink software are executed.As the verification of the former analyses, the experiments of the single pump and the double-pump close loop system are performed. The experiments of the piezoelectric vibrating film, the optimum working frequency of the micropump are studied. The close loop focusing system reaches the basic characteristics of the liquid tunable focal length lens with the accuracy control of the microfluidic volume.