Construction Of Flexible Wearable Sensors And Its Applications In Health Monitoring

Flexible and wearable sensors are electronic devices like human skin manufactured using flexible electronic technology,which shows the capability of sensing health information.It can convert stimulation signals into visual electrical signals in the form of signal conduction to help humans acquiring physical and chemical information from the environment and the human body,and can be used in humancomputer interaction systems,soft robots,medical equipment,etc.The sensors have the advantages of low cost,simple preparation process,light volume,convenient wearing,and high stability.In addition,the sensors can be utilized to monitor various health information such as breathing,pulse,heartbeat,and components in sweat in real-time,which exhibits important application prospects in the prevention and early diagnosis of diseases.However,most wearable sensors still exist the problems of the complex preparation process,complex structure,low sensitivity,single detection method,single detection target,and poor skin fit,which limit the application of the sensor.Therefore,we fabricate a variety of flexible and wearable sensors by utilizing pNIPAm as the core material.We are committed to improving the sensitivity,detection method,detection target and adhesion to skin of the sensors by exploring the materials,compositions,and structures of the sensors.Finally,the sensors are utilized to record physiological health signals to further expand their applications in the field of medical and health diagnosis.The main results are listed below:1.A strategy is proposed for preparing flexible and wearable sensors to obtain multiple outputs and realize super-high sensitivity.In this work,a highly sensitive flexible and wearable pressure sensor with a sandwich structure was developed using a nano-sized porous pNIPAm microgel as the sensing layer and two thin silver layers as the bottom/top electrodes,respectively.The single-layer structure of the microgel film allows the sensor exhibits dual outputs of optical and electronic signals in response to pressure changes.At the same time,the sensor exhibits a high-pressure sensitivity(10.1 kPa-1)and low minimum detection pressure(2 Pa),which enables it to monitor various physiological health signals in real-time to diagnose physical health in a wearable style.The sensor has been successfully applied to monitor a series of human physiological activities,such as speaking,swallowing,breathing,pulse,heartbeat,etc.The detection results are wirelessly sent to a smartphone by Bluetooth and are displayed through home-made software.This makes it very convenient to use at home or in the office.2.A fabrication strategy for fabricating multi-functional wearable sensors is proposed.In this work,a flexible and wearable sensor with high sensitivity and multitarget detection was fabricated by integrating a single-layer Au@pNIPAm microgel into the middle of two gold electrode layers.The conformational changes of microgel polymer chains due to physiological signals and metabolites in body fluids induce measurable capacitive signals generated by the sensors.The conformational changes in the microgel polymer chains due to physiological signals and metabolites in body fluids induce morphological changes in the single-layer microgel structure,which results in changes in capacitive signals from the sensors.Therefore,the acquisition and analysis of the target can be achieved by recording the capacitive signal of the sensor.To study the application of the sensor,this multipurpose sensor was used to detect bacteria such as E.coli and B.subitilis,metabolites such as uric acid in sweat,and physiological signals such as sound recognition,respiration,and pulse beat.The multifunctional detection characteristics of the sensor further broaden its application potential in real life.3.A novel poly(Cu-NIPAm)hydrogel based on the interpenetrating network of poly(Cu-arylacetylene)and pNIPAm was developed.The poly(Cu-arylacetylide)chains allow the hydrogels good electron conduction.The accumulation of the Cuarylacetylide backbones inhibits the swelling behavior of the hydrogels in physiological environments.The poly(Cu-arylacetylide)component of the hydrogel leads to excellent bacterial resistance.The hydrogels also show negligible cytotoxicity and immunological rejection,lending them for use as wearable and implantable sensors.To evaluate their application,the hydrogels-based sensor firstly was demonstrated for recording an electrocardiogram and electromyogram.Secondly,the hydrogel-based sensors were implanted on the heart surfaces of rats to obtain epicardial ECG,which exhibits stable signals during four weeks of application.Thirdly,the hydrogel was fashioned into nerve guidance conduits to bridge two distal stumps of injured sciatic nerves in rat legs,which exhibit the excellent transmission capability of neural signals.This work not only creates a new research field of hydrogels but advances the technical design concepts for implantable sensors to efficiently record bioelectronic signals.