Construction And Application Of Paper-Based Chips For Sweat,Mercury Ions And Motion Sensing

The problem of low medical resources has plagued mankind.Large devices,which are complex to use and expensive,are difficult to popularize in economically underdeveloped regions.Even in developed countries with these technologies,people also need to be time-consuming waiting for the acquisition of detection results.Point-of-care testing（POCT）has great potential in coping with early disease diagnosis,health monitoring.Paper is an inexpensive,ubiquitous,renewable material and has many characteristics such as good biocompatibility and capillarity.Microfluidic paper-based chips/microfluidic paper-based analytical devices（μPADs）,using paper as a substrate for point-of-care assays,have become popular among the leading devices for POCT because of its portability,low cost,and ease of use.Colorimetric detection was an important detection method inμPADs,which have an intuitive reading effect and no need for other equipment.However,the presence of negative effects such as the coffee ring effect leads to uneven color and poor detection results.Therefore,it is necessary to modify paper to solve the above problems.Meanwhile,as a paradigm for the application of paper in motion sensing and health monitoring,the substrate of paper-based pressure sensors has the advantages of flexibility,expanded integration,portability.But shortcomings such as cumbersome and expensive modification methods,and narrow detection range limit its application in more environments.In this paper,paper-based chips as the research core,biomarkers or human motion situations that are instructive in disease screening and health monitoring were selected as the detection targets.Three kinds of paper-based chips by functionalizing filter paper or depositing functional nanomaterials were successfully fabricated.While achieving the above detection target analysis,the problem of color distribution in colorimetric paper-based chips and large reading error in distance-based method was also ameliorated.The main work of this thesis includes the following three aspects:1.A microfluidic paper-based chip（tri-PAD）was fabricated to detect three biomarkers（p H,Cl^-,and glucose）.Methyl red-methylene blue indicator doped with cationic surfactant Cetrimonium bromide（CTAB）was selected as the p H detection reagent.The doping of CTAB tethered the indicator,and changed the dissociation constant to achieve quantitative detection in the range of p H 4.0-7.0.The detection of Cl^-was based on the Mohr titration method,and the prepared paper chip was able to detect 40-160 m M of Cl^-based on the discoloration distance.By depositing amino-modified composite nanomaterials on paper,the immobilization of enzymes and chromogenic agents was achieved,improving the uniformity and depth of color.The glucose PAD enabled sensitive detection of 50-1600μM glucose with a detection limit of 1.23μM.The fabricated tri-PAD has been successfully used in real sweat samples.The tri-PAD was able to make an initial judgment of the degree of motility as well as aid in the initial screening of patients with skin disorders,cystic fibrosis and diabetes.2.A polystyrene nanoparticles（PS NPs）modified paper-based microfluidic chip（PS-μPAD）was proposed to enhance the clarity of discoloration boundary in distance-based detection.The hydrophobic region was constructed by the optimized drawing method to prepareμPAD.PS NPs with carboxyl groups on the surface were deposited in the channels of the chip,and PS-μPAD with dual functions of delaying flow rates and hydrogen bond fixation was fabricated.Using a mercury ion probe as a functional verification,the paper-based chip could achieve distance-based quantitative detection of Hg²⁺ions,while increased the color depth difference inside and outside of the discoloration boundary by four times.And the standard deviation of subjective readings reduced by nearly 75%.In addition,the prepared PS-μPAD had strong scalability and could replace mercury ion probes with other probes that can bind to carboxyl groups to achieve the detection of other substances.3.A paper-based pressure sensor modified with polypyrrole was prepared and was applied to capture and monitor changes in human movements.Through chemical vapor deposition and optimization of preparation conditions,polypyrrole modified conductive paper with a double-sided resistance below 50Ωwas obtained.Stack conductive paper to fabricate a pressure sensor,and the number of stacked layers was optimized to 4.In addition,multiple paper-based pressure sensors were also connected in series as an array to achieve multi-point pressure change detection.The fabricated paper-based pressure sensor had the properties of sensitive and rapid detection of action change,and has potential application in monitoring human motion and movement changes.In summary,three kinds of paper-based chips applied in biological or environmental sample testing and motion monitoring were designed and fabricated in this paper.The detection of biomarkers in sweat,Hg²⁺ions and human motion was achieved through functionalizing or depositing functional materials and imparted different functionalities to the paper-based chips.Strategies for optimization of the detection results with certain applicability had also been proposed.This study provided new ideas for the application of microfluidic paper-based chips in the field of point of care testing.