Research On Flexible Sensors Based On Elastic Fibers And Fabrics

In recent years,highly elastic wearable sensing technology has been promoted and developed faster with the emergence and popularization of emerging applications such as health management monitoring,human movement assistance,communication technology and artificial intelligence.Highly elastic stretchable strain sensors overcome the shortcomings of traditional strain sensors that are prone to failure when repeatedly and highly stretched,and have developed rapidly due to advantages such as wearability,instant detection and non-invasiveness.The rapid development of human-computer interaction,sports health monitoring and other subdivisions has put forward higher requirements for sensors.There is an urgent need for elastic sensing technology with flexible,bendable,stretchable,and recoverable characteristics to meet the comfort of human wearing demand.In this project,CM800 elastic fiber and its fabrics with different porosity were used as the base material and graphene was used as the functional agent.Graphene-modified materials were prepared by dipping and screen printing methods and fabricated into flexible textile-based sensors.Its structures,performance and applications in sensors were discussed.The main research contents are as follows:(1)Graphene-modified CM800 fibers were prepared by dipping method and their applications in sensors were discussed.Morphology and structure of graphene-modified CM800 fibers were characterized by SEM.And the electrical conductivity and sensing performance were tested.The results showed that the flexible substrate had good electrical conductivity.When the strain in the weft direction was less than 18.5%,the gauge factor was1.96 and the resistance change rate had a linear relationship with strain,which could be used for the detection of subtle deformations such as blood pressure and respiration.In a reversibility test with 0.2% strain applied,the coil structure was broken in balance and shifted to a new balance.The modified CM800 fiber was woven into twisted braid and other structures by hand-weaving method and was worn on the human body in the form of bracelets,necklaces and rings to test the sensing performance of the human body under different motions.(2)Graphene-modified mono-and bi-elastic fiber-covered yarns were prepared by dipping method.And their performance was tested by digital four-probe tester,parameter analyzer and stepping motor controller.The results showed that the modified covered yarn had strong electrical conductivity and washability.The conductivity after washing was reduced from 5.98 to 5.43 S/m,and the GF of fabricated sensor based mono-elastic fiber-covered yarn under 0-17%、17%-19.5% and 19.5%-25% strain were 29.2、28.64 and10.48.Compared with that of bi-elastic fiber-covered yarns,the sensor based mono-CM800fiber-covered spandex had better elasticity and sensitivity.It also had both high elongation and resilience,which had potential application in the field of wearable textile.(3)Graphene-modified CM800 knitted fabrics were prepared by screen printing and flexible strain sensors were developed.The sensing characteristics such as the relationship between resistance change rate and strain based on the constant elongation tensile test were analyzed and compared with traditional spandex knitted fabric strain sensor.The results showed that the new elastic knitted fabric strain sensor was linear with the increase of strain and had fantastic resistance change rate,high sensitivity and wide linear working range.In the strain range of 0%-40% and 80%-100%,GF was 33.6 and 54.8,respectively.In addition,the graphene-based sensor also possessed other excellent properties,such as cycling stability and well hysteresis.Connected the above-prepared textile-based strain sensors to different parts of the human body to detect various human physiological activity signals such as relatively large bending movements of hands,arms and legs,force on the soles of the feet and relatively small amplitudes of breathing,muscle vibrations during speaking,heartbeat,sleeping position and intraocular pressure.The monitoring of daily physiological activities of patients,children and the elderly based on flexible textile-based strain sensors has broad application prospects.