A Capillary-evaporation Micropump For Monitoring Flow Rate In Real-time

Human sweat consists of abundant physiological information reflecting health conditions,so by testing and analyzing in vitro key biomarkers such as glucose and chloride in sweat,diseases like diabetes and pulmonary cystic fibrosis can be diagnosed.Therefore,the sweating rate can not only affect the measurement of key biomarkers,but also early warn the risk of dehydration during exercise,which can be conducive to making personalized rehydration strategies.However,traditional methods of sweat collection followed by off-line component detection have many drawbacks,for example,the sample is at high risk of contamination and the analysis is too delayed to get real-time health information.Rapid development of microfluidic technology offers the possibility of sweat collection and real-time monitoring owing to its excellent fluid-driven capacity and biocompatibility.Nowadays,micropumps driven by capillarity or osmosis have lower driving forces and lack methods of real-time monitoring sweating rate,which makes it impossible to achieve long-term sweat collection and monitoring.In this study,by combining the capillary-evaporation effect and the electrochemical detection principle,a micropump with strong driving force is designed to collect and monitor the sweating rate in real time.The micropump and the peripheral system including a programmable syringe pump,an electrochemical workstation and a computer form the in-vitro experiment system,which together serve to achieve functions of liquid loading,flow rate monitoring and data analysis.In this thesis,the author studied functions of collecting fluids and monitoring flow rate.Detailed contents include:(1)Based on the principle of capillary-evaporation effect,a micropump device that can monitor the sweating rate in real time is designed.It includes a micro-channel structure based on the principle of capillary absorbing and transmitting liquids,an evaporation zone driving the liquid flow,and a sensing zone with the integrated three-electrode,which not only collects sweat automatically but also monitors the sweating rate in real time;(2)Based on the evaporation model of sessile drops,the simulation software is used to simulate the process of the micropump driving the liquid flow by capillary-evaporation effect.The numerical simulation results of the fluid flow rate driven by the capillary-evaporationeffect in the microchannel,the evaporation rate of the orifice array at the evaporation outlet,and the maximum pumping rate of the micropump are shown;(3)The micropump and the peripheral system including a programmable syringe pump,an electrochemical workstation and a computer constitute the in-vitro experiment system which exploits the normal saline to simulate sweat,and by experiments,it is verified that the capillary effect is effective to fill the microchannel and the evaporation effect is effective to pump fluid.Then the three-electrode is further used to monitor the maximum pumping flow of the micropump.As a result,the experimental results are consistent with the simulation results,which verifies the feasibility of the micropump monitoring the flow rate in real time.Due to the merits that the capillary-evaporation effect has a stronger driving force and can run for a long time,and the electrochemical detection technology is real-time with high sensitivity,low power and is easily integrated in the device,the micropump designed in this paper to collect and monitor sweat in real time provides a certain theoretical and methodological basis for the further study of wearable equipment monitoring sweat.