Preparation And Strain Sensing Properties Of Bionic Thermoplastic Polyurethane Composite Fiber Membrane

Flexible sensing materials have attracted more and more attention from researchers in electronic skin,medical monitoring,environmental monitoring,visual transmission and speech recognition due to their good stretchability,stability and wearability.In recent years,flexible sensors based on conductive polymer composites(CPCs)have shown great development potential in various fields due to their advantages,such as low cost,easy processing,good flexibility and light weight.How to effectively resolve the contradiction between sensitivity and stretchable range,and integrate functions such as high stretchability,high sensitivity,low detection limit and visual sensing into the same element is still a huge challenge.In this article,inspired by the structure and function of natural organisms,multilayer flexible strain sensing materials and strain sensors with visual sensing function were prepared by imitating the multilayer structure of mussels and the structure of cephalopod epidermis,respectively.The influence of the material microstructure on the performance of the strain sensor was studied,the relationship between the structure and performance of the sensing material was analyzed,and the strain response behavior and photoluminescence properties of the sensor were studied.In addition,the materials are used in applications such as human health monitoring,sign language recognition and visual transmission.The specific research content and results are as follows:1、Inspired by the mussel structure,the biomimetic multilayer flexible strain sensing material(MGTSS)was prepared by electrostatic spinning and high-pressure spraying.Based on the interaction between multilayer structures,the sensor shows a wide strain detection range and good stability.TPU fiber membrane as a flexible substrate gives the material good flexibility.Two-dimensional MXene nanosheets are bridged with graphene(r GO)by Ti-O-C covalent bond,and the conductive network has a good stimulus-response function.The microstructure of the nanofiber membrane was characterized by scanning electron microscope(SEM).The distribution of conductive filler on the fiber was stable and uniform.Transmission electron microscopy(TEM)was used to analyze the microstructures of MXene nanosheets and r GO nanosheets.For the interaction force between MXene and r GO,the chemical states of each component were analyzed by X-ray photoelectron spectroscopy(XPS),and the reaction mechanism was deduced.Through material microstructure design,this study alleviates the contradiction between the high sensitivity of strain sensor and the large strain response range,and provides a new idea for the design and preparation of the next generation of high-performance wearable sensors.2、The strain sensing and bending sensing properties of MGTSS were studied.It was found that based on the Ti-O-C covalent bond generated between MXene and r GO nanosheets and the nacre-mimetic multilayer structure,the MGTSS achieves high sensitivity(GF>84326),large detection range(0-200%),fast response time(70 ms),low detection limit(0.05% strain)and good cycle stability(more than 5000stretching/releasing cycles).Based on the microstructure analysis of the material,the evolution mechanism of the conductive network of the sensor is studied,which provides a theoretical reference for the development of a new generation of strain sensors with high sensitivity and wide working range.MGTSS was attached to the relevant parts of the human body for human motion detection,pulse monitoring and sign language recognition,and good online test results were obtained.This material shows a good application prospect in the field of flexible wearable.3、Inspired by the controlled luminescence properties of cephalopod epidermal microstructure,a highly stretchable TPU electrospun fiber film mixed with fluorescent agent(FA)was used as flexible substrates,and carbon nanotube(CNTs)ink was used as optical shielding layer and conductive layer.The surface of FA/TPU fiber was coated with CNTs ink by ultrasonic method,and then the strain-dependent microcrack structure was constructed by pre-stretching,and a biomimetic visual flexible sensor based on CNTs/FA/TPU fluorescent fiber membrane(CFTM)was prepared.The material can work normally under 200% large strain,detect small strain as low as 0.01%and achieve stable signal output.The material also has a fast response time(30 ms)and good response stability,with the material still showing good response after 2000 tests.In the photoluminescence response test,CFTM successfully achieved the visual sensing performance of strain variation during the tensile cycle thanks to the unique microcrack structure of the prefabricated CNTs ink and its good UV shielding performance.The flexible sensor assembled based on the material is attached to the human hand,elbow,leg and other parts,realizing a good visual online human movement monitoring function.