Wearable Microfluidic Thread/Paper-based Colorimetric System And Its Application In Human Sweat Analysis

Point-of-care testing(POCT)is a rapid and sensitive analytical method that can be performed beside patients.In the past decade,great progress has been achieved in its research.Wearable POCT devices can be implanted in or non-invasively attached on human body to achieve on-site detection of biomarkers,which greatly alleviate patients' pain and discomfort.Wearable POCT devices have already demonstrated great potentials in daily healthcare,especially in the diagnosis of chronic diseases.Sweat secreted by human body during exercise,stress or exposure to high temperature has attracted much attention in recent years as a very promising non-invasive analytical biofluid due to its easy collection and rich chemical information.If wearable POCT technology can be combined with sweat analysis,it will provide a window for further understanding the dynamic changes of biological molecules in human body,as well as a new means for daily healthcare and disease diagnosis.Thread and paper are easily accessible materials,which meet the requirements of wearable devices on flexibility and biocompatibility.This thesis innovatively combines them for the construction of a microfluidic thread/paper-based analysis device(?TPAD).By coupling with the smartphone,the analysis system has been successfully used for human sweat detection.The main contents of this thesis are as follows: 1.Tailoring wicking property of cotton thread via plasma treatmentThread is twisted by two or more fibers.The gap between the fibers provides a channel for liquid to flow through capillary force.In order to effectively enhance capillary force and accelerate liquid transport,plasma was applied to remove wax from the thread surface and generate more hydrophilic groups on the fiber surface.The wicking property and hydrophilicity of cotton thread are characterized by the average flow velocity and contact angle,respectively.The wicking property and hydrophilicity of the thread can be controlled by changing the plasma treatment mode and treatment duration.It is found that the wicking capability could be improved by straightening and fixing the cotton thread during the treatment process.With the prolongation of treatment duration,the wicking capability would gradually increase,but after 40 seconds,it tends to be stable.In order to overcome the loss of wicking capability after long-term exposure in air,effects of onestep and multiple-step plasma treatments were applied.Results show that the wicking property and hydrophilicity can be effectively prolonged by repeated treatment.2.Single-channel ?TPAD and its application in sweat glucose analysisIn this part,a wearable ?TPAD containing a cotton thread and a functionalized filter paper was developed for non-invasive,quantitative and in situ monitoring of human sweat glucose with the assistance of a smartphone.Amounts of enzymes and reagents on the filter papers were optimized to achieve the high-performance colorimetric sensing of glucose.The as-prepared device possesses a dynamic range of 50 to 250 ?? and a detection limit of ~35 ??.Because of its great wearability and compatibility with conventional textile industry,the ?TPAD was integrated with an arm guard to sensitively detect glucose in human sweat.Through comparative analysis with blood glucose level,it is found that there are two orders of magnitude differences between sweat glucose and blood glucose,but there is a high correlation between them.3.?TPAD with Y-shaped channel and its application in sweat pH and lactate analysisHerein,the design of the ?TPAD colorimetric device was optimized to manufacture a microfluidic thread/paper-based analytical system consisting of a sweat reservoir and a multi-sensing component for simultaneous in situ analysis of sweat pH and lactate.To achieve the transport of sweat from the reservoir to the paper-based sensors,two hydrophilic silk threads are twisted and knotted to form a Y-shaped structure for efficient separation of the liquid sample.The paper-based colorimetric sensors in the system were prepared by dropping lactate detection reagents and the universal pH indicator complemented with trace alkaline,respectively.The smartphone-based quantitative analysis shows that the sensors are sensitive and reliable.The linear detection ranges of the two sensors are pH 4.0-8.0 and 1.0-25.0 mM,respectively.The orientation and thread shape have no influence on the sweat flow.Although pH may interfere the lactate detection,the pH detected simultaneously could be employed to correct the measured data for the achievement of a precise lactate level.After being integrated with a hydrophobic arm guard,the system was successfully used for the on-body measurement of pH and lactate in the sweats secreted from the volunteers.This thesis not only extends the application of thread-based microfluidic devices in human sweat analysis,but also provides a very promising method for manufacturing the read/paper-based wearable POCT noninvasive diagnostic system.