Wearable Microfluidic Devices For Sweat Sampling And Their Physical Parameters Optimization

Recently,wearable microfluidic?MF?devices have been paid great attention by researchers due to their special structures and good performances,which can effectively monitor body fluids in real-time.By mounting to skin,MF devices can easily collect body fluids such as saliva,sweat and tear,quickly analyze and transmit data.The obtained results of physical health can provide important indicators,including real-time monitoring of vital physiology signs and analyzing related disease diagnosis.However,the reported advances on wearable microfluidics are still in laboratory small-scale fabrication in a given condition.In order to develop an industrial product,there are still many problems to be solved,as well as costs and biocompatible materials.Calibration and other key technical indicators need to be solved before commercial application.The present medical human silicone rubber is two-component addition molding room temperature SiS₂ rubber,compared with Ecoflex and Dow Corning 184,not only its curing temperature and cost are lower,but also its chemical stability,biocompatibility and replication evenness are better.There are many fields of application.The main work of this paper is to combine the excellent performance of medical human silicone rubber with microfluidic chip,and to exert its advantages to promote the commercialization of wearable microfluidic.The main work of this paper is as follows:?1?Microfluidic chips were prepared by using medical silicone rubber to solve the problem of high cost of microfluidic chips.The template was prepared by laser and mechanical engraving to solve the loss problem of the template.The thickness of the microfluidic cover plate was analyzed.The optimum thickness of the cover plate was 0.12 mm,and the uniform adhesive velocity of the cover plate was 2500 rpm/s.The causes of the collapse of the cavity due to the thin cover plate and the poor flexibility of the microfluidic chip due to the overthickness of the cover plate are analyzed.The curing temperature of medical silicone rubber was analyzed in detail.It was found that when the curing temperature was 60?,there were no bubbles in the silicone rubber and the curing time was the shortest.The hydrophilic modification of microfluidic channels with hydrophobic surface was carried out by in vitro simulation tests,so that the samples tested in vitro did not affect the practical use.At the same time,the samples which were simulated successfully in vitro were collected and tested outside the body sweat.?2?The accuracy of sweat color recognition in microfluidic cavity was improved by adding hydrogel reagent.The concrete performance is that when sweat enters the microfluidic channel,it can react with color,be easily recognized by APP,and solve the problem that the visual effect of sweat is not obvious.The hydrogel color reagent is prepared by the reaction of oil bath pot,its process is simple and easy to operate,and the cost is low.In this paper,the parameters of hydrogel were optimized to shorten the color response time as much as possible,in which the mass fraction of initiator and crosslinker was 0.3%,0.8%and 90%,respectively.When the reaction temperature is 70?,the response time of the hydrogel is the shortest and the shortest time is 20 s.?3?A flexible microfluidic chip with closed side microfluidic cavity with tail filter paper structure is designed to realize the real-time collection of liquid.The performance comparison between this structure and the reported microfluidic for real-time collection shows that the chip has good closeness and can effectively avoid evaporation of collected liquids.Further comparative experiments were carried out on different silica gel materials,and it was found that ordinary medical human silica gel had less liquid permeability than Tao Kangning PDMS.Finally,the structure was applied to the detection of hydrogen peroxide concentration and urine composition,and the calibration curve of hydrogen peroxide concentration was made to verify its effectiveness.