Real-Time Sensing Characteristics Of Flexible Sweat Sensor Based On Microfluidic System

Sweat is a very important body fluid,which is rich in biomarkers such as metabolites,proteins,hormones and electrolytes.The concentration of these biomarkers provides important information about physiological states and diseases.For example,metabolic alkalosis can be non-invasively characterized by measuring the p H value of sweat,the glucose concentration in sweat varies with diet and exercise,and testing for sweat sugar levels can provide information about diabetes status and exercise performance,the sodium ion and chloride ion concentrations in sweat are closely related to dehydration.Recent advances in sweat sensing applications have proven that sweat is an excellent candidate for non-invasive continuous health monitoring.As more biomarkers are identified in sweat,it is expected that sweat testing will expand into more and more practical medical applications.At present,new wearable flexible sweat sensors based on different detection methods have been used for continuous human health monitoring,but there are still many deficiencies in real-time continuous human sweat detection,and many problems need to be solved urgently.For most of the flexible sweat sensors based on electrochemical sensing,they often collect sweat directly from the body surface for detection.The defects of sweat,such as easy evaporation and easy contamination,will affect the accuracy of the test results.For the electrochemical sweat sensor combined with micro-flow channel,although the old sweat can be guided out of the detection area,the separation effect of the old sweat is not obvious,and the old sweat still remains in the detection area,so the real-time detection cannot be realized.For colorimetric sweat sensor based on micro flow channel,it can only achieve half quantitative measurement,sensing accuracy need to be improved.In view of the above problem,this article is based on micro flow channel structure design,respectively,the preparation of the microchannel network can be used for the colorimetric detection,can be used for electrochemical sensing microchannel network and the combination of real time continuous sweat sensing electrochemical sensor and flexible sweat sensor of color sensor,the this article main research results are as follows:?1?First,based on previous studies on bursting pressure,the relationship between blast pressure and channel width w and divergence angle?was analyzed in detail.Second,experimentally explore the minimum burst pressure difference?P_pbetween adjacent blasting valves that can be sampled sequentially,and then design the micro-fluid channel system based on the minimum burst pressure difference.Use Abaqus and COMSOL Multiphysics software to simulate deformation under various strains and changes in the volume fraction of the liquid as it passes through the blast valve and the pressure at the blast valve.Finally,a flexible microchannel structure was prepared by the inverted mold method,and the feasibility of sequential sampling and the stability of the rectangular microchannel system under mechanical disturbance were verified by experiments.?2?The theoretical analysis of the relationship between the capillary pressure in the capillary pump and the mainstream channel width w₁ and the micro-pillar spacing w₂ is detailed.Then,the effect of the structure size and initial injection rate of the capillary pump on the filling time of the liquid in the capillary pump was experimentally investigated.Electrochemical sensors were then prepared and tested.Specifically,electrodes were fabricated on PI films using laser-induced graphene technology and chemically modified to form glucose sensors and sodium ion sensors.Performance tests were performed on glucose and sodium ion sensors.Finally,the capillary pump and the electrochemical sensor were integrated into a microfluidic device,and the analytes were quantitatively measured in real time.The role of the capillary flow pump in separating new and old sweat and detecting the analytes in real time was explored.?3?Through the theoretical analysis of the previous two parts,a capillary flow pump with a high capillary pressure and a suitable capillary bursting valve were designed,and they were combined into the same microfluidic network.The unique filling effect of filling the colorimetric region after preferentially filling the electrochemical region was verified by experiments.Secondly,the performance test of the colorimetric sensor and the electrochemical sensor was followed.Finally,the sensor is integrated into the microfluidic network,the effect of capillary flow pump on the real-time detection of analyte concentration and the effect of colorimetric sensing region where the capillary bursting valve was located on the detection of analyte concentration in time sequence were verified.The results show that real-time continuous sweat detection can be effectively achieved.