| With the development of society and the improvement of science and technology,human requirements in smart wearable devices are increasing.In recent years,smart wearable device has shown a huge growth trend with the development of various disciplines such as artificial intelligence,Internet of Things technology,communication technology,and material science.The collection and utilization of physiological signals related to the human body,such as pressure,humidity,temperature and other information,are the foundation of big data services for operations under extreme environment such as high temperature,sports health,and medical industries.Based on the collection and processing of various human body signals,the working environment conditions be adjusted in time,so that to correct training suggestions or put forward diagnosis and treatment plans.Therefore,the flexible sensors are of great significance for realizing remote emergency processing.The flexibile sensors become the research hotspots in recent years.The long-term collection of various signals of the human body requires stability,portability,comfort,and recyclability.Therefore,in this paper,spinning technology,based on fiber and yarn materials,supplemented by the special structural advantages of core-sheath composite yarn,was used to construct a functional flexible sensor with capacitance,current,voltage,etc.as detection signals.Theoretical analysis and experimental verification of the sensor's sensing mechanism are conducted in this paper.In addition,by using the flexible sensors,human health signals such as respiration as well as human movement signals are monitored,and the signal detection and transmission required in special environments based on all-fiber sensors are realized,which has important academic significance and potential application value.The main research contents and results of the thesis are as follows.First of all,based on the principle of four-axis feeding spinning method,we independently built a wrapping spinning system device,and prepared a composite yarn based on a core-sheath structure with copper wire as the core yarn and special-shaped cross-section polyester filament as the sheath yarn.The surface morphology of the filaments with different cross-sections was characterized,and the humidity-sensitive properties of the filaments with different surface and cross-sectional morphologies were analyzed.By observing the cross-sectional morphology of the special-shaped fibers,it is concluded that the cross-sections of such fibers are all non-circular,with grooves in the longitudinal direction.Through statistical calculation of cross-sectional images of special-shaped polyester fibers,the difference in specific surface area is analyzed.And the water molecule transmission ability of special-shaped cross-section fibers is compared through an experimental platform for testing the water molecule transmission capacity of the fibers.Finally,through predictive calculation and experimental verification,it is concluded that the larger the specific surface area of the special-shaped cross-section fiber,the easier it is to absorb and desorb water molecules.The grooved shape of the special-shaped cross-section fiber not only affects the water molecule transport capacity of a single fiber,but also affects the water transport performance of the yarn composed of such special-shaped cross-section fibers.Based on the grooves of such fibers form gaps in the yarn assembly and the capillary effect,water molecules can easily transfer from the wet side to the dry side and quickly evaporate.On this basis,capacitance based humidity sensors with different profiled cross-sectional yarns were developed,and the humidity-electrical responsitive performance such as sensitivity,response time of these composite yarn sensors are systematicly analyzed and compared.The influencing factors of the composite yarn humidity sensor are clarified,the humidity-sensing performance of the special-shaped cross-section fiber is analyzed,and the humidity sensing model of the full-fiber composite yarn is proposed.Secondly,based on the working principle and definition of the single-electrode mode nanogenerator,and combined with the characteristics of the core-sheath structure composite yarn in the two-axis feeding spinning method,the preparation method of the all-fiber yarn and fabric based triboelectric nanogenerator is explored.A method for mass production of this functional yarn and fabric was clarified,and a triboelectric nanogenerator based on the core-sheath structure of polyimide yarn and silver-plated conductive filament was constructed.In addition,the yarns and fabrics' properties are systematically characterized.The durability of the yarn was explored through washing and flame-retardant tests,and the results showed that the composite yarn has stable performance and will not cause obvious damage or performance degradation after washing or burning tests.The electrical performance shows that the composite yarn nanogenerator has an electrical output of 0.230-0.295 ?A under the test frequency condition from 1 Hz to 2.5 Hz.In addition,the yarn electricity output increases with the yarn length increasing.At the same time,the composite yarn nanogenerator can withstand mechanical blows and friction during the weaving process.Five kinds of woven fabrics with different structures were prepared by a small sample loom machine.The results show that these fabrics have good flexibility and air permeability.The difference in electrical outputs of these fabrics with different tissue structures are compared.In a word,the preparation method of the triboelectic nanogenerator from yarn to fabric is systematically constructed,and the parameters of continuous production of all-fiber yarn and fabric nanogenerator are clarified.The physical and mechanical properties of the core-sheath composite yarn nanogenerator are analyzed.In addition,an all-fiber core-sheath structured composite yarn and its fabric triboelectric nanogenerator with acid-and alkali-resistant functionality are developed.The composite yarn is composed of polytetrafluoroethylene shell filaments and silver-plated conductive core yarn.The hydrophobicity analysis of the yarn and its fabric were carried out by in-situ observation and static contact angle analysis.By dipping samples into concentrated acid solution(concentrated alkali solution)and comparing the changes in appearance and electrical output performance,the composite yarn and weaved fabrics for acid and alkali resistance performance were compared.When the droplets are contacted and separated from the yarn and fabric,an electrical signal will be generated,which is explored for the first time.The electron transfer mechanism generated by the contact separation between the droplets and the yarn is also analyzed.The results showed that the electrical output generated by the contact and separation between the droplets and fabric emhanced with the increase of the flow rate.In addition,the electrical output performance of the yarns with different lengths,different test frequencies and contact materials are characterized.As the length of composite yarns increases,the output of short-circuit current,shortcircuit charge and open-circuit voltage increase,and the short-circuit current of the yarn increases with test frequency becomes faster.The effectiveness and reliability of this type of composite yarn as an intelligent and functional textile material are verified.Finally,based on the flexible sensor of the core-sheath composite yarn,a smart mask that can monitor human breathing,smart joint protectors that can monitor joint movement health information,and smart textiles that require information transmission in other application scenarios are constructed.The flexible humidity sensor is fixed on the breathing valve of the ordinary 3M mask,and the capacitance signal change of the humidity sensor is measured in real time to detect human breathing frequency,breathing intensity and respiratory arrest,and finally realize the function of monitoring human breathing.In order to establish the framework of the intelligent platform of the remote respiratory monitoring system,the humidity sensor can be connected to the circuit board with functions such as wireless charging,data filtering and information transmission,and the final monitored signal can be displayed on terminals such as mobile phones.The data can also be uploaded,stored and shared through the cloud,which is also convenient for later processing and analysis.The yarn nanogenerator is sewn on wristpads,elbowpads,kneepads,anklepads and other parts,and the correlation between the electrical output signal changes when the human joints are bent is used to realize joint motion detection and signal analysis.A self-powered escape and rescue system with flame retardant performance was also prepared by using the yarn nanogenerator.Through the connection and arrangement of the LED light and the fabric nanogenerator,an escape system that displays the best escape route in real time is constructed.At the same time,through the multi-channel acquisition card,a rescue system that displays the precise location for help in real time on the rescue terminal can be realized.Based on the hydrophobicity,acid resistance and alkali resistance of the PTFE yarn nanogenerator,an intelligent protective clothing system was established by sewing the yarn and its fabric on ordinary clean clothes.On the basis of realizing the antichemical function,it utlized a multi-channel acquisition system to realize real-time signal detection and transmission.This thesis systematically analyzes the sensor response mechanism,mechanical properties and mass production method of the composite yarn sensor with core-sheath structure.The humiditycapacitance behavior and humidity response mechanism of the core-sheath composite yarn sensor are analyzed,and the structure formation,sensing mechanism and application of the yarn humidity sensor are also developed.At the same time,the electrical response mechanism of the contact and separation of nanogenerator based on the core-sheath structure composite yarn is analyzed,and the mass-produced processing method and process parameters are proposed,the continuous production of the yarn nanogenerator is provided.The research results and theoretical basis have enriched the application range of sensors in the field of smart textiles such as detection of human motion,health information,detection of extreme environments and signal transmission. |
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