Study Of Silver/Poly (Amic Acid) Composite Structure And Its Flexible Sensing Characteristics

In recent years,with the increasing demand for flexible electronic devices,highperformance flexible sensors have attracted widespread attention.However,these sensors still cannot achieve high sensitivity and high flexibility simultaneously.To this point,it is necessary to develop unique new material preparation and processing technologies.Polymer metallization used widely in flexible electronics has attracted much attention.In this work,the composite structure of silver/poly(amic acid)(PAA)was prepared by low temperature solution method.The back propagation neural network model based on differential evolution algorithm(DE-BPNN)was used to optimize the process parameters to achieve either high resistance or high conductivity.The optimized process parameters are obtained,and the electrical and mechanical properties of the material are studied.The application of this composite structure in flexible sensor is explored to achieve high sensitivity and wide strain range.The main content of this thesis is as the following:1.Based on surface modification and ion exchange technology,the in-situ growth of the metal silver layer on the surface of PAA is realized,and the Ag/PAA composite structure is obtained.With the DE-BPNN optimized process parameters,the controllable preparation of high-resistance or high-conductivity composite structures was achieved.Four process parameters such as PAA concentration,Ag NO3 ion exchange time,Na BH4 concentration and reduction time were selected as the input of DE-BPNN,and the product of Ag/PAA sheet resistance and total process time was used as the output.1077 sets of process parameters were selected as learning samples.The DE-BPNN model was established,and the optimized growth conditions of high-resistance and highconductivity composites were obtained.Another 49 sets of process parameters were selected as test samples to evaluate the model accuracy.The results indicated that the obtained relative error is no more than 1.96%.The results implied that the established DE-BPNN model can provide the global optimal solution of process parameters.2.According to the established DE-BPNN model,the flexible sensing characteristics of the Ag/PAA composite structure were studied,and the resistive strain sensor and the capacitive pressure sensor array were prepared,respectively.The high-resistance Ag/PAA composite structure was used as the strain-sensitive material,and the high-conductivity Ag/PAA composite structure was used as the conductive electrode.The results show that the strain sensor with high-resistance Ag/PAA composite structure has the maximum gauge factor of 7.49 and the maximum strain range of 1% to 9%.It can withstand 8000 bending stress tests without degradation.All these showed that the optimized sensor has better stability than the one with materials without model optimization.The lowresistance Ag/PAA composite structure satisfies the requirements of the electrode.And the prepared capacitive array sensor can measure the pressure value change in real time.3.The low temperature solution chemical annealing method is used to improve the defects of the surface metal layer and further improve the performance of the Ag/PAA composite structure.With the selected halogen salt solution,the defects of the surface metal silver layer were improved by the immersion treatment,in which silver nano particles(Ag NPs)can be melted by the halogen salt.The results showed that in the high-conductivity Ag/PAA composite structure,the chemical annealing of 1wt% Na I solution for 50 s can reduce the surface sheet resistance by 18.2%.For the high-resistance Ag/PAA composite structure,the effect of chemical annealing on electrical resistance is not obvious.