Design And Self-healing Properties Of Flexible Textile Sensors

With the advent of the 5G era,the Internet of Things has developed rapidly,and people's demand for smart wearable devices is increasing.Among them,flexible strain sensors,as the core component of human-computer interaction in smart wearable devices,have received extensive attention and research from scholars at home and abroad.Among many flexible strain sensors,textile flexible strain sensors are considered to be the most ideal flexible strain sensors due to their excellent flexibility,air permeability,controllable structure and industrialization.Although ordinary textile sensors have high sensitivity and flexibility,they are susceptible to accidental damage such as wear,scratches,and irreversible deformation during actual use,which will not only reduce the service life of textile flexible sensors,but also greatly reduce the operation of the sensor stability.It has become a research hotspot at home and abroad to extend the service life and operational stability of the sensor by introducing the selfrepair function into the textile flexible sensor.Therefore,in order to solve irreversible deformation damage and fracture damage,this paper synthesized a polyurethane with shape memory function or self-repairing function,and combined it with a textile flexible sensor to prepare a textile flexible sensor with self-repairing function.The main research contents are as follows:The first part is the self-repair of the irreversible deformation damage of the fabric sensor.Firstly,a polyurethane with shape memory function is synthesized and a knitted conductive fabric is prepared using a computerized flat knitting machine,and then the conductive knitted fabric is encapsulated by polyurethane to obtain a knitted fabric flexible sensor.The prepared knitted fabric sensor has high stretchability and excellent resilience,and exhibits high sensitivity,low hysteresis,operation stability under different deformations,and high cycle durability in the test of sensing performance.At the same time,the sensor is applied to human body detection,and it is found that it can be used to accurately detect large movements of the human body(such as joint bending)and subtle movements(such as voice recognition).The most important thing is that the self-repairing ability of the sensor is given by the prepared shape memory polyurethane.When the sensor is over-stretched and causes irreversible deformation to cause the sensor to fail,the sensor can be restored to its original shape under human body temperature or water environment.The self-repair of the sensor greatly extends the service life of the sensor.In the second part of the thesis,the work is to self-repair the fracture damage of the fibrous strain sensor.Firstly,the self-healing polyurethane is synthesized and mixed with high-elastic polyurethane for wet spinning to obtain polyurethane fiber with both self-healing and high elasticity.Then,carbon nanotubes(MWCNTs)were coated on the fiber surface by ultrasonic to prepare fiber flexible sensor.While maximizing the retention of self-healing properties,the effect of the content of highly elastic polyurethane on fiber elasticity was explored.The fiber flexible sensor finally prepared has a stretching range of 750%,high sensitivity(GF=60.4)and a wide detection range greater than 200%,while also exhibiting low hysteresis and high cycle durability.The fiber sensor inherits the self-healing function of the polymer matrix.When heated at80 ? for 3 h,the damaged sensor can realize the self-repair of its mechanical and electrical properties.After self-repair,the sensor's sensing performance is basically the same as that of the undamaged device,demonstrating its huge application prospects in smart textiles.