Publication: Synthesis of stretchable conductive polymer for electronics circuit application
No Thumbnail Available
Date
2023-04-01
Authors
Sana Zulfiqar
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Stretchable electronic circuits (SECs) have become very popular nowadays in various mechanical, electrical and biomedical engineering applications. They are comprised of flexible and stretchable substrate as well as conductive ink, and electronic components. The stretchability and flexibility of SECs can be controlled by the proper selection of materials and designs for the substrate and conductive ink. Moreover, the material used to develop the conductive ink must exhibit high electrical conductivity and good adhesion with the substrate to obtain a high quality of stretchable printed circuit. This study focussed on the synthesis, material modelling and the examination of various properties of polymeric substrate and conductive ink by different thermal, mechanical and electrical testing. For synthesis, PDMS-OH was used as a binder or elastomer in both the formulations and silver powder as a conductive filler for silver-based conductive ink. The mechanical properties of these materials were evaluated by simple UTM under tensile loading. The modulus of elasticity and tensile strength of the substrate and ink were found as 0.48 MPa and 2.18 MPa at 300% stretchability, and 5.72 MPa and 1.195 MPa with the yield stress of 0.86 MPa at 137% stretchability before rupture, respectively. Afterwards, the thermal analysis of the conductive ink was carried out by DSC and TGA. From DSC, the glass transition and melting temperatures of the cured ink were found as 130°C and 297.43°C, correspondingly. The thermal degradation was studied by TGA in which the weight loss occurred at different ranges of temperature. The residue of silver particles was obtained as 82.62% after complete analysis. This proves that the current formulation of the ink becomes more viscous at higher temperatures. Moreover, the storage modulus, loss modulus and damping ratio of the ink were calculated using DMA analysis. As a result, the silver ink exhibited low loss modulus value than the storage modulus, which proves that the current formulation of the ink was more elastic in nature rather viscous. Farther the micro mechanical analysis, the hardness and reduced modulus of the conductive were computed by nanoindentation technique. In addition, the surface analysis of the ink was done by OM and SEM. As a result, the silver particles were homogeneously spread throughout the surface of the ink. The electrical conductivity was measured by 2-point multi-meter before and after application of load. It was found as 1002 S/cm without loading, while, the resistance of the ink increased from 0.042 Ω to 25 Ω at 60% strain during loading and decreased from 25 Ω to 0.0767 Ω at 0% after unloading. Finally, the stress-strain data of respective material were utilized to characterize the material properties using hyper-elastic constitutive models for the substrate and multi-linear plastic models for the conductive ink. The curve fitting was done using three solvers, Abaqus, GRG and C-PSO algorithm. As a consequence, the Reduced Polynomial (𝑁=6) model under C-PSO algorithm was considered as the best fit hyper-elastic model than others. The validation of this hyper-elastic model was then executed through FE analysis. Consequently, the experimental results were in a good agreement with the simulated results.