The Fabrication And Study Of Strain Sensing Performance Of Conductive Polymer Composites Through The Adjustment Of PDMS Microstructure

In general,conductive polymer composites(CPCs)are fabricated by incorporating conductive fillers into polymer matrices.The diversity of their structure and function has aroused considerable attention for researchers.Moreover,functional CPCs are applied in many fields due to which show a variety of abundant response behavior.As one of the significant aspects,the flexible and stretchable sensors have performed a broad application prospects in the detection of human health,the diagnosis of disease and flexible robot,etc.In this paper,based on the design and control of structure of CPCs,we prepared the CPCs with different microstructures and explored the response behaviors under the external stimuli.The major results are shown as follows:1.The fabrication and properties of the wrinkled CNTs/PDMS and “sandwiched” PDMS/CNTs/PDMS CPCsIn this paper,the wrinkled PDMS films are prepared by the formation of double membrane structure and mechanical stretching–releasing method.The spray coating method is used to form the CNTs/PDMS CPCs with high transparent and wrinkle structure.The transparency of pure film,acidification and spraying CNTs film are explored,and the distribution of CNTs on the wrinkle surface is analyzed.The distribution of CNTs is uniformity without obvious aggregation and the fabricated CNTs/PDMS film with a higher transparent.The hydrophobicity of acidification and untreated PDMS films are studied.Compared with the untreated PDMS film,the elongation at break has a certain decrease.The CNTs/PDMS film with wrinkle structure shows a significant response for the different deformations and the resistance can return to the initial value during the cyclic strain process.However,the stability of strain-resistance behavior is poor.In order to enhance the stability of the micro-structure and conductive pathway of the film,the PDMS/CNTs/PDMS CPCs with “sandwich” structure is prepared.The relationship between the number of spraying of the "sandwich" structure films and the transparency and resistance is investigated.The transparency of the fabricated film is high and the response rate(265 ms)shows a significant improvement compared to the unstructured CNTs/PDMS film(400 ms),and as high as the wrinkled CNTs/PDMS film(260 ms).And the “sandwich” conductive film shows a good response for the large strain,which is due to the wrinkle structure that provides a stretching space to delay the tensile effect on the damage of the conductive network.After 2000 cycles,the resistance can return to the initial value,which indicates that the PDMS/CNTs/PDMS strain sensor with good stability.Therefore,the process of constructing the “sandwich” structure is available to enhance the stability of strain sensing behavior of the flexible CPCs.2.The fabrication and strain sensing properties of CI/PDMS CPCs with crack structureIn this paper,a double membrane structure of the PDMS film is prepared by acid oxidation method,and the flexible strain sensor is fabricated with crack structure through mechanical stretching and spraying conductive ink.The characterization and width statistics of cracks formed by different acidification time is performed.The distribution of the conductive ink on the surface of film with and without stretching is studied,and the response behavior under deformation of the samples prepared by the two processes is compared.The fabricated strain sensor possesses a very high sensitivity to the strain,the response time is only 90 ms,and the strain response range more than 100%.It has a significant response to different strains.After 10000 cycles,the resistance of the strain sensor can still return to the initial value,indicating that it possesses excellent durability and stability.And,the film can perform opposite response behavior for the different bending directions(compression and tension).Moreover,the flexible and wearable strain sensor based on the assembly of this film can online monitoring a large set of human movements,such as joint bending,sound,facial expression,pulse and so on.And the types and times of the human movement can be judged by analyzing the collected figures,such as waves and amplitudes.Which indicates that the fabricated film exhibits profound potential for human health monitoring and intelligent electronic devices,the design and control for the structure of the fabricated materials also provides a new idea for the preparation of high performance flexible wearable strain sensors.