Research On Wearable Electrochemical Sensors In Health Monitoring And On-site Detection

With the development of the Internet of Things and micro-nano processing technology,wearable electrochemical sensors have shown great potential in real-time detection.However,as an up-and-coming intelligent electronic in the past decade,it still faces many challenges in commercial application,such as high production costs,poor environmental applicability,and low accuracy and precision in actual sample detection.In this thesis,sensor arrays were fabricated through screen-printing technology.Starting from the electrochemical sensing mechanism,sensing process was established based on a specific electrocatalytic reaction,a new method for in-situ electrodeposition was developed to reduce detection limits,the composition of crystal face was controlled to improve sensing selectivity,composite materials were designed to improve sensitivity.Through the above ideas,insufficient precision and accuracy of wearable electrochemical sensors in health monitoring and on-site detection can be solved.According to the methanol electrochemical oxidation process catalyzed by platinum catalyst,methanol sensors with dual environmental applicability were designed and prepared through screen-printing technology on a variety of flexible substrates,which exhibited high selectivity,fast response and recovery process（<200 s）,good stability（10-15 days）in the linear detection range of methanol gas（0-20%）and liquid（0-6%）under room temperature.On the basis of this study,a "sacrificial template-based in-situ electrodeposition" method was developed.Combined this co-electrodeposition method with screen printing technology,porous structures were in-situ prepared on the surface of screen-printed working electrode for heavy metal sensing,the detection limit of Pb2+,Cu2+and Hg2+ analysis was reduced by increasing the number of active adsorption sites,the sensing accuracy of heavy metal detection in real samples was improved.And,this sensor with porous structure can realize the stable response without lag in the process of real-time detection.By changing the type and proportion of precursors,other porous membrane structures can be directly extended to in situ preparation and applied to related analytes detection.Using Cu₂O as the electrocatalyst for enzyme-free glucose sensing process,the controllable preparation of Cu₂O with different morphologies（octahedral,quasi-spherical and extended hexapods）was realized by adjusting the ratio of precursors.The study showed that there is a dependency relationship between the catalytic activity and the crystal face.The higher the ratio of {100}/{111},the more favorable it is to achieve high sensitivity at lower over potentials for highly selective enzyme-free glucose catalysis.Among them,quasi-spherical Cu₂O showed the best sensing performance,and the initial oxidation potential was 0.3 V,the linear detection range was 0-12 mM,the detection limit was 3.5 μM.The quasi-spherical Cu₂O can be used as an enzyme-free electrocatalyst for the application of wearable glucose sensors and non-enzymebased biofuel cells.Based on the moisture-sensitive properties of silk protein contraction-stretching and the reversible band gap change of graphene under different humidity conditions,silk fibroingraphene composite films（SF-G）with different ratios were designed and prepared for humidity sensing by using natural silk and natural graphite as raw materials.The results showed that,when the ratio of silk fibroin（SF）to graphene oxide（GO）was 1:1,the reduction degree and defects of the composites were the highest.Based on the surface with rich folds and regular interlayer structure,the SF-G（SF:GO=1:1）composites exhibited good sensitivity for humidity sensing,which was 33 times of that of graphene.The sensor had a fast and stable linear response in the range of 0-97%RH,and the response and recovery time were 0.01 s.The dynamic test results showed,SF-G based humidity sensor can realize non-contact fingertip humidity detection at a distance of 1 cm and respiratory rate monitoring during movement.