A Bionic Micropump Based On Stomatal Transpiration Mechanism In Plants

One of key techniques in Miniaturized Total Analysis System is microfluidic driving and controlling technique. As an important component of micro fluidic drive systems, micropump has many applications such as drug delivery system, micro fluidic supply, chip integrated cooling systems, biotechnology and microchemical engineering.The mechanism and impetus of water uptake in plant were investigated and analyzed. In plants, stomatal transpiration drives the mass flow of liquid water from the roots to the leaves. Edge effect regard the vapor diffuse effectively through micropores, and the nanochannel meniscus among mesophyll cells can produce additional pressure, negative pressure which is induced by mesophyll regard cause water flow along vascular in xylem.In this paper, a biomimetic microfluidics micropump based on stomatal transpiration in plants is developed. And microfluidic drive system consists of microfluidics chip, sampling system and flow rate adjust module is fabricated. This work includes:(1) Simulating the mechanism of negative pressure introduced by stomatal transpiration, we design the main structure contains two film, The pump is mainly composed of a250-μm thick SU-8lamina and an agarose gel sheet. The micropores array in the SU-8plate is used to imitate the stomata in the leaf, and the agarose gel sheet mimic mesophyll cell around substomatal chamber. Water vapor diffuses into air through micropores,-which lead to the lose of water in the micropump chamber. The negative pressure induced by the nanopores in gel sheet drives the fluid from the reservoir to the target site. The flow rate can be regulated by changing the number of the micropores participated in transpiration, and it can be adjusted by shield-adjust unit in the pump.(2) The PDMS base-chip and cover-chip were fabricated through molding method, The microfluidic chips were fabricated through plasma linkage. A new interface mechanism is designed to connect chip with micropipe for multiple Interface. A manipulate platform, which is used to form microfluidic drive system, is fabricated for flow rate test in microchannel.(3) With the microfluidic drive system, we test flow rate variation and stability of biomimetic micropump, micropore cover unit is usefull for flow rate adjust. The measurement device with a long channel chip is designed to check water potential against gravity, and bubbles in water plug will limit ascend hight. Also,the effects of ambient temperature and air current on flow rate is tested.Results have shown that the steady flow rate of the pump in the nl/min range could be obtained, and its relative standard deviation(RSD)can be controlled within±5%.