Preparation And Research Of Silk Fabric Based Flexible Strain Sensors

In recent years,wearable electronic products have emerged rapidly,and become a hot topic because of their great application value and market prospect in medical health,motion detection and other fields.However,obtaining flexible sensors with high sensitivity and wide sensing range through simple and economical methods still faces great challenges.A carbonized silk fabric(CSF)with an average resistance of 107.4? was obtained by degumming treatment and high temperature carbonized using natural silk fabric as raw material,and it was combined with elastic matrix(PDMS)to obtain a flexible strain sensor with high sensitivity and wide response range(CSF@PDMS);Secondly,the effect of fabric density and woven structure on the sensing performance of silk-based fabrics were studied,and the sensing mechanism of fabric-based wearable electronic products was explored.The main conclusions are as follows:(1)The influence of silk degumming process on sensing performance was investigated.The effect of temperature,treatment time,reagent type on the sensing performance was mainly studied,it was found that the structure of silk fibroin was destroyed when the temperature was too high and the treatment time was too long.Among them,the degumming rate was 10.49% and the CSF average resistance was 107.4? after 8 mol/l urea treated for 3h with 80?.Further verification by Raman spectroscopy showed that it had a more perfect six-membered ring structure;after combined with PDMS substrate,the sensitivity of the obtained flexible sensor was 160.87 in the sensing range of 0-150%.The results show that the suitable degumming process is beneficial to the transition of carbonized silk to better conductive material,which is very important to achieving high sensitivity and large sensing range.(2)The effect of weaving structure and fabric density on sensing properties of silk was investigated.Through comparing the properties of silk after carbonization,we found that the CSF of warp and weft twisted in the same direction has better sensing performance,the GF is up to184.79 and the sensing range is 0-100%.But for the two fabrics of double joe and double crepe,the properties are different under different fabric densities,and it was found that under 15 and 18 mm,double joe and double crepe achieved the best performance,which the average sensitivity was 62.26 and 63.28 respectively with excellent sensing range.(3)The sensing mechanism of fabric-based flexible strain sensors was explored.The carbon fiber flexible sensor(CF@PDMS)was prepared by using carbon fiber(CF)beam simulated yarn in the CSF,and its fracture form was observed by optical microscope.We found that CF had poor adhesion to the elastic matrix and formed multiple channels inside it,so that short fibers broken in tensile state could slip back and forth along the direction of force to form a conductive path,resulting in electrical signal change,which could not restore the original resistance value after recovery;the slip change of short fibers in the matrix was an important reason for sensitivity,cycle stability and recognizability.(4)CSF@PDM flexible sensor was successfully applied to human motion detection and a flexible keyboard was designed and fabricated.Through the detailed study of degumming process and woven structure,a strain sensor with a sensitivity of 184.79 and a deformation range of0-100% is prepared,which can accurately identify fingers and multiple motion positions with different bending angles(30°,60°,90°).In addition,the sensor can be well used to prepare a touch flexible keyboard which have excellent recognition?sensitive and stability.In concluded,the flexible strain sensor prepared by carbonized silk fabric has both high sensitivity and wide sensing range,it can be used in large scale deformation and weak signal detection which exhibits huge potential of applications in wearable devices.