Study And Application Of Deformation Performance On Pre-coated Silver Nanowire Flexible Metal Film Strain Sensor

Structural health monitoring is an intelligent system that monitors the "healthy state" of the structure in real time by using various sensors as nervous system to sense and predict structural internal defects and damages.Because of the good flexibility and durability,applications of thin film strain sensor in structural health monitoring are becoming more and more extensive.To avoid conductive failures under external loads and corrosion in extreme environments,a flexible strain sensor was fabricated by a polymer/metal/polymer sandwich structure film embedded with silver nanowires.We have carried out some work around structural characterization,factors influencing the electrical conductivity,durability,and potential applications in structural health monitoring.1.The effect of the weight ratio of PDMS and curing agent on the tensile property of PDMS film was studied in detail.According to the heating time and stretching ratio,the weight ratio of 10:1 was taken during the preparation process.Scanning electron microscope was used to detect the sensor surface to analyze the good durability and conductivity of the sensor.2.The effects of film size and ambient temperature on the conductivity of the sensor were studied separately,and linear relationship between different influencing factors and resistance changes were fitted.Not only that,the effect of the bending radius on electrical conductivity was studied.To illustrate the applicability of bending deformation in practical applications,the sensor was connected with the index finger and elbow and the resistance change was measured under the movement of various muscles.3.The combination of Ag film and AgNWs enabled the composite conductive film to be used as a high-sensitivity strain sensor with gauge factors of 7.1 at a strain of 0-10%and 21.1 at a strain of 10-30%.The strain sensor proved to be highly reversible and remained stable after 1000 bending cycles.These results indicated that AgNWs could act as an elastic conductive bridge across the cracks in the metal film,allowing the sensor to maintain high conductivity under tensile and bending loads.In addition,the PDMS coating could effectively prevent the conductive layer from contacting with the external saline environment,which showed that the sensor can be applied to structural health monitoring in salt water environment.4.The sensor connected on the steel sheet was applied in the real time detection of micro strain in the tensile test.The strain sensor could return to the initial resistance value after 3 times of repeated loading-unloading at the strain of 3000 με.And the relationship between resistance change and strain illustrated high linear relationship and sensitivity.The strain sensor prepared in this paper could maintain good conductivity and durability under tensile and bending loads.The sensor was prepared with a sandwich structure by PDMS and conductive layer and the PDMS coating could prevent the conductive layer from the external environment effectively.The good durability and anti-corrosion property of the conductive film showed the highly potential application to be used as a flexible strain sensor in salt water condition and monitor the micro-strain in real time of the structure.