Research Of Preparation And Properties Of Fiber-shaped Strain Sensor Based On Carbon-based Conductive Solution

Fibrous stretchable stress/strain sensors have gained a lot of attention in the field of wearable electronics and real-time monitoring of human motion health signals due to their small size and ability to be integrated into clothing.By using the buckled structure,strain sensors with large strain sensing range and good stability can be obtained.However,the preparation of buckled structures using vertical arrays of carbon nanotubes is difficult to obtain and costly;powder-like materials with cost advantages are difficult to form buckled structures on the fiber surface.Making fibers into porous structures is also capable of strain sensing,but usually with insufficient stability.Thus,it is still a challenge to construct a more reasonable stretchable strain sensor structure to improve the sensitivity and stretch range while enhancing the cyclic stability.In this work,we designed a buckled structure and porous structure on the surface of stretchable elastic fiber,optimized the ratio of conductive ink,and pretreated the surface of elastic fiber substrate to enhance the bonding between conductive functional layer and elastic fiber,and finally obtained an elastic conductive fiber with excellent tensile sensing characteristics,low cost and simple preparation process.First,the configuration of low-cost conductive inks and the preparation of surface buckled structures were investigated.By adding SEBs to the dispersion of carbon-based conductive materials,the dispersion and film formation of pure carbon-based materials on the fiber surface are improved,the homogeneity and flexibility of the conductive functional layer are improved,the dispersed CNTs are integrated and connected into a thin film,and finally a sheath-core buckled structure is formed on the surface of the elastic fibers to obtain conductive elastic conductive fibers with good strain sensing characteristics.In addition,pretreatment of the elastic fiber substrate by SEBs/oil solution enhances the bonding between the elastic fiber substrate and the conductive functional layer,further enhancing the stability of the resistance change during strain in composites with buckled structures.The cost of the conductive ink obtained by this method is reduced by about 97 % compared to the cost of carbon nanotube array preparation.Subsequently,conductive fibers with buckled structure were made using CNTs/SEBs conductive ink,and their electrical properties,mechanical properties and strain sensing properties were investigated.We investigated the preparation process of the buckled structure and the effect of the conductive ink content on the performance of the strain sensor.It was found that the spraying method was more effective in obtaining a continuous,uniform and adjustable thickness of the conductive functional layer;the conductivity of the elastic conductive fibers increased as the content of the carbon-based conductive material in the conductive ink increased.The strain-sensing fibers with adjustable diameters from 35 ?m to 500 ?m can be produced by the above method.The optimized parameters allow the fibers to reach a conductivity of 97.17 S/m,a response time of 62 ms,a stretching range of 200 %,and repeated stretching up to more than 28,000 times at 100 % strain.Finally,a conductive functional layer with porous structure is formed on the surface of elastic fiber by spraying method and Breath Figures(BFs)to explore its conductive properties,sensing performance and application in daily life.We investigated the effects of the conductive ink ratio,the gun aperture and the gun distance from the sample on the surface morphology of the porous structure.It was found that as the content of SEBs in the conductive ink increased,the CNTs on the surface of the elastic conductive fiber was gradually wrapped in the SEBs,the diameter of the porous structure decreased significantly,the surface morphology of the porous structure gradually tended to smooth,and the conductivity of the elastic conductive fiber also decreased significantly.In addition,the size of the spray gun aperture is also an important factor affecting the morphology of the porous structure,and the diameter and distribution of the porous structure tended to be homogeneous and stable as the aperture size decreased.After optimization,the surface of the elastic conductive fiber has a uniform and regular porous structure,the diameter of the elastic conductive fiber can be as low as 58 ?m,and it can withstand 240 % of the applied strain with a sensitivity of 1299.07 and a response time of 62.7 ms with almost no hysteresis,and has up to100,000 repeated tensile cycles at 100 %,which is significantly higher than other fibershaped strain sensors with porous structures reported in the literature.By integrating the manufactured elastic conductive fibers into the gloves,the smart gloves made are able to exhibit specific changes in resistance signals for different gestures.