Researches On The Microfluidic System For Multi-liquid Mixing

During the last two decades, with the demand of the stability and accuracy in the field of the biochemistry, a new emerging field called microfluidics has been brought about. Its advantages are low reagent consumption, faster analyzing and totally analyzing and so on. While in the mcirofluidic systems, the mixing of the multi-liquid on different ratios is often happened. And the mixing accuracy is the very important to the microfluidic systems. In this paper, based on the review of the micro fluidic systems and micropumps, a mcirofluidic system which consists of two novel micropumps has been proposed. Its advantages are low input voltage, high output, high security, portability and high accuracy. This microfluidic system would be widely used in the field of biological science and chemical analysisIn this paper two novel micropumps are proposed, one is the PDMS diaphragm actuated by EO (electroosmotic) actuator and the other is the PDMS diaphragm actuated by ICPF (Ion Conducting Polymer Film) actuator. Firstly, the working priciple of the EO actuator and ICPF actuator has been analyzed. Then two diaphragm micropumps have been designed and fabricated by MEMS technologies in lab. A fuel cell has been explored to solve the problem of the water electrolyzed so that the EO actuator can be used continuously for a long time. A sealed chamber has been designed in order to combine the ICPF bending force and thermopneumatic force together to get high performance. The optimum duty ratio and frequency have been found by the experimental and theoretical methods. The factors which influence the output of the microfluidic system have been discussed.After the analysis of hysteresis nonlinear model in the past researches, Bouc-Wen model has been chosen to identify the hysteresis of the PDMS diaphragm micropump. Firstly, hysteresis nonlinear characteristic of PDMS diaphragm micropump has been analyzed quantitatively by Hilbert transformation. Secondly, the hysteresis nonlinear model has been established according to the mechanism of PDMS diaphragm micropump. Thirdly, parameters of hysteresis nonlinear model are identified by optimized least squares method on the basis of above first and second step. So the precise mathematical model can be provided in order to control output flow precisely.In the close loop of the multi-liquid mixing microfluidic system, the object is PDMS diaphragm micropump which is structure-known, parameters-uncertain and time-varying. On the basis of this characteristic, the model reference adaptive control scheme has been chosen to obtain the precise output flow. And this control scheme has been verified to control accurately through digital simulation and actual experiment. It possesses good robust characteristic, too. Acid-base neutralization experiment is also designed to test the performance of multi-liquid mixing microfluidic system.To sum up, the PDMS diaphragm micropumps actuated by EO actuator and ICPF actuator are the core of the microfluidic system of multi-liquid mixing. And this mcirofluidic system can be proved to control and mix flow, which will play a very important role in chemical and biological fields.