Micropore Diffusion Mechanism Of Bionic Micropump

As the premise and key technology in the utlilize and development of microfluidic chip, microfluidic driving has attracted a number of researchers’attention and made the experiments of Biology, chemistry, medicine possible. In this work, a new method of microfluidic driving depending on the transpiration theory of plant had been introduced.Vapor diffuse effectively through stomata. Diffusion flux of stomata can achieve dozens of times of diffusion flux of free water surface.The theory used in this article mainly includes the transport of water in plant and transpiration of pore. Stomatal transpiration was simulated and analyzed in this paper. Main contents are as follows:(1) The water could be absorbed to the plant from soil by the plant root and raised to the leaf by the press which comes from the transpiration. The rising of water is successful due to the molecular cohesion.(2) A mathematical model had been set up by the theory of transpiration and simulated by COMSOL Multiphysics to analysis the diffusion process when the water passed the micro-pore array. The relation between the diffusion speed of water and pore had been studied by the diffusion flux of water in pore arrays with different pore size and pore distance. It can be seen that the diffusion speed should be increased by addition of pore distance or decreasing the pore size and influenced by fringe effect in the process of transpiration.(3) A micro-pump consisted of micro-pore film, porous medium and liquid storage pool had been designed and fabricated to simulate the plant transpiration. The micro-pore film with micro-pore array of SU-8glue was used to simulate the pore array in plant which could make the water diffusing to the outside. The porous medium made by hydrophilic and porous ceramic was use to simulate the cells in the plant leaf where there are many three-dimensional and micro/nano channel, which applied a large surface of transpiration. The bottom layer included a water channel connected to the liquid storage pool and a drainage channel used to remove the remaining water.(4) Flow rate of biomimetic micropump with different micro-pore film was measured. Effects of pore size and distribution on pore transpiration were evaluated based on the flow rate of micropump. Comparing experimental results and simulation results, Effects of stomata size and distribution on stomatal transpiration were is similar.The transpiration influences by pore size and distribution makes a high speed of water diffusion, which is dozens of times than the water with same area. The relation between the diffusion speed of water and pore size and distance had been studied by the fluid rate of micro-pump with different micro-pore films. Simulation and experiment results showed that edge effect existed in the process of stomatal transpiration, and with the increase of distance between pores and decrease of pore size, weaker interference between pores, higher diffusion rate.