| Sweat is a kind of fluid secreted by sweat glands.It contains rich electrolytes and molecules and has great potential in disease diagnosis and health monitoring.Compared with other body fluids,such as urine,blood,saliva,sweat is particularly attractive and gradually becomes an important choice in diagnosis,due to its ease collection and non-invasive generation.With the advancement of materials and technologies,in-situ sweat analysis was proposed to implement the real-time and continuous detection and thus avoid contamination problems caused by too many sample operations.Continuous detection could also provide the dynamic curves of the metabolites and obtain more physiological information.In recent years,more and more attention has focused on in-situ sweat analysis on human skin,but there are still some challenges to address.For example,during continuous in-situ sweat analysis,if the old sweat could not flow away from the detection area,it will cause the accumulation of sweat under the sensors leading to the mixture of old and new sweat,and then affecting the accuracy of detection.In addition,when it comes to the detection of ions contained in sweat,traditional ion sensors,due to their large size and complex fabrication process,make it hard to be integrated into wearable devices.This hinders the development of in-situ sweat detection.Moreover,how to integrate the biosensors and wearable devices sweamlessly is the key challenge in promote in-situ sweat detection.And the advancement of wearable devices integrated with the functions of electrochemical detection will not only help obtain more knowledge about sweat physiological health,but also accelerate the commercialization of in-situ sweat analysis technology.Considering the problems mentioned above,this paper focused on the in-situ sweat detection and performed deep research,aiming at solving the existing problems in this field.First of all,three-dimensional paper-based microfluidic devices featured with low-cost and simple fabrication,was proposed for sweat collection and diversion,avoiding sweat accumulation and the mixture of old and new sweat.Secondly,unlike the traditional ion-selective electrodes,an all-solid ion-selective electrode with the merits of simple,light-weight,and easy-fabrication,was proposed for sweat detection.Furthermore,a smartwatch integrated with electrochemical detection platform was developed,which could be combined with three-dimensional microfluidic devices and all-solid ion sensors for in-situ detecting ions in sweat.Finally,a sensor array and an electrochemical detection circuit based on flexible printed circuit board were proposed to achieve real-time multiple-parameter in-situ sweat analysis.The main research work and innovations in this paper are presented as follows:1)Firstly,in order to solve the problems of sweat accumulation and the mixture of new and old sweat during in-situ sweat detection,a 3D paper-based microfluidic device(3D-PMD)by screen-printing technology was developed in this paper.Inspired by the capillary effect of filter paper,3D-PMD was fabricated,the hydrophobic layer of which was modified by wax screen-printing on the filter paper,and then the three-dimensional channel was formed after the process of cutting and folding.In 3D-PMD,sweat collected could flow horizontally and vertically.Moreover,optimization study was performed to reduce the sample consumption in sweat collector included in 3D-PMD.And two 3D-PMD with different sizes were fabricated to meet the requirements of different sensor sizes.3D-PMD presented here not only solved the problems of sweat accumulation,but also separated the sensor from the skin to reduce the risk of sensor contamination.2)Secondly,a glucose electrochemical sensor was prepared by layer-by-layer modifying the sensitive elements onto the surface of carbon electrode fabricated by screen-printing.The sensor had a wide detection range(5?M?1900?M),which covered the physiological range of glucose in sweat.In this paper,3D-PMD was integrated with the glucose sensor to perform in-situ glucose detection in sweat on human skin during exercise.The results indicated that the integrated sweat glucose detection device successfully obtained the dynamic curves of glucose in body sweat,and the test data could be further used to analyze the physiological changes of glucose during exercise.The proposed integrated device here has the advantages of low-cost,simple-fabrication and disposablility with a good application prospect in the field of in-situ sweat analysis on human skin.3)Prepare all-solid-state ion-selective electrodes for sweat ions analysis.In this paper,Na~+and K~+ion-selective electrodes were prepared by modifying screen-printing electrodes with ion-selective membranes.Then,the prepared electrodes were characterized respectively.The results showed that both of Na~+and K~+ion-selective electrodes had wide detection ranges(Na~+:8 m M?128 m M;K~+:1 m M?32 m M);good selectivity and repeatability;high consistency(RSD<3.5%);long-term stability of 5.5 hours(superior to other ion-selective electrodes);and storage time up to14 days.Compared with the reported ones,these all-solid ion selective sensors in this paper has the advantages of flexibility,low-cost,mass-production,and disposablility,which can be used for sweat ions detection,and has a good application prospect.4)Further,to promote the development of sweat analysis and the advancement of sweat research,a smartwatch system functionalized with ion-detection capability was developed in this paper,which could accelerate the commercialization of sweat monitoring.The circuit system in the smartwatch mainly included the functions of dual-channel ion detection,power management,and LCD display.The ion detection system was established by open circuit potential detection circuit.Then,the smartwatch,ion-selective sensors,and the developed 3D-PMD were integrated together for real-time monitoring Na~+and K~+in body sweat.And on-body test experiments were designed to achieve dynamic detection of sweat ions in motion scenes.The developed smartwatch,as one of wearable devices,has the characteristics and functions of low power consumption,wireless transmission and real-time display,which is of great practical significance.5)A sensor array and wearable detection circuit based on FPCB material was developed.The electrode array was prepared on FPCB as a mechanical flexible substrate by screen-printing technology.And Na~+,K~+,p H and glucose sensors were respectively fabricated by modifying sensitive elements onto the SPE.A wearable FPCB detection circuit was designed to connect with the sensor array and realize the synchronous detection of multiple-parameter biomarkers in sweat.Meanwhile,a mobile phone application was also developed for receiving the sweat detection data and real-time displaying the levels of multiple sweat markers.Finally,the multi-parameter real-time detection experiment of body sweat was designed to verify the practical application ability of this integrated device.The sensor array and detection circuit based on FPCB developed in this paper has the advantages of low cost and mass production,which has good practical application value.Moreover,this wearable device is suitable for wearing multiple body parts,which has good research and application value. |
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