Construction Of Wearable Devices For Controllable Sweat Collection And In Situ Multiplexed Detection

Recently,the rapid development of flexible wearable devices has completely revolutionized people’s lifestyles.Wearable sweat sensors enable non-invasive,real-time,and continuous analysis of physiological markers at the molecular level,displaying a wide application prospect in health management,medical care,clinical diagnosis,etc.However,human sweat features tiny volume,high volatility,vulnerability to epidermal pollution,and low-abundant biomarkers.Therefore,reliable collection and detection strategies are two important factors of wearable sweat sensors.The traditional sweat sampling technology is complex to operate,where the collection and detection are separately performed.In this paper,we design superwettable bandage,Janus gauze,Janus silk textile,and epidermal microfluidic chip for collecting sweat in a well-defined,unidirectional,and dynamic manner,respectively.By combining these sweat-collecting devices with colorimetric,electrochemical,and surface-enhanced Raman spectrum(SERS)analytical techniques,we realize in situ and multiplexed detection of sweat.These wearable devices remarkably enrich sweat collection and sensing systems.The main contents of the dissertation are as follows:1.Superwettable bandages for fixed-point sweat sampling and colorimetric sensing:we develop a superwettable colorimetric sweat bandage.The superhydrophobic background coating limits the irregular flowing and diffusion of sweat microdroplets,while the superhydrophilic sites selectively absorb and anchor sweat microdroplets.The combination of these two interfaces creates superhydrophobic-superhydrophilic micropatterns and provides precise sweat sampling regions.The superhydrophilic sites are deposited by colorimetric reagents for in situ colorimetric sweat analysis.A smartphone-based color analysis APP is adopted to read the corresponding color value of each superhydrophilic assay site,achieving semi-quantitatively detection of sweat pH,glucose,chloride,and calcium ion.This facile,portable,and low-cost superwettable colorimetric bandage holds great potential in the point-of-care test(POCT)field.2.Janus gauze for unidirectional sweat collection and electrochemical detection.We construct a Janus gauze-based electrochemical patch,where the core sweat sampling component of Janus gauze consists of hydrophobic polyurethane(PU)nanofibers and hydrophilic medical gauze on two opposite sides.This unique structure drives the unidirectional and spontaneous transfer of sweat from the hydrophobic side(skin side)to the hydrophilic side of Janus gauze.The nanodendritic gold electrode arrays are configured on the hydrophilic side for simultaneous detection of sweat glucose,lactic acid,K+,and Na+.Compared to traditional textiles,this Janus gauze allows the centralized distribution of sweat on the electrode surface,providing new possibilities for exploring precise and controllable biofluid sensing interfaces.3.Janus silk E-textiles with wet-thermal comfort for highly-efficient biofluid monitoring.The silk textiles with Janus wettability and their unidirectional sweat sampling characteristics not only eliminate the wet/sticky discomfort caused by sweat on the skin,but also generate a smart epidermal thermal management effect:cooling down when sweating and maintaining warming when resting.The silk yarn electrodes coated with carbon paint are woven on the hydrophilic side of Janus silk fabric to create Janus silk electronic textiles.The sweat is unidirectionally transported to the hydrophilic side(electrode side),which significantly reduces the required volumetric threshold(<5 μL)and response time(reduced by～2-3 min)for electrochemical sensing.This research provides a new pathway for the design of flexible sensors with wearable comfort.4.Epidermal microfluidic plasmonic chip for dynamic sweat sampling and SERS sensing.In this system,the epidermal microfluidic chip continuously siphons sweat into the internal microchamber.The microchamber is equipped with a SERS substrate of Ag nanomushroom arrays.Both simulation and experimental results show its fine Raman enhancement effect(～106).By using a portable Raman analyzer,this microfluidic SERS system achieves rapid detection of sweat urea,lactic acid,and pH value,greatly expanding the application scenarios of Raman analysis technology in the wearable sensors field.Integrating such a microfluidic device and SERS analytical techniques meets the requirement of dynamic and refreshable sweat collection as well as SERS analysis,providing a new method for the development of wearable SERS sweat sensors.