Study of inkjet-printed serpentine structure on flexible substrates deformed over sculptured surfaces

The electrical resistance of inkjet-printed silver structures on polymer substrates deformed over complex sculptured surfaces is studied in this work. Mating sculptured surfaces with complex surfaces are designed and fabricated using 3D additive printing of plastic materials. These sculptured fixtures are fabricated to be able to be fit onto a universal test machine. Two types of surfaces are considered in this study: (1) biaxial or dome-shaped bending to produce bi-axial tension on the printed elements and (2) convex/concave saddle-like bending to produce bi-axial tension and compression on the printed elements. Conductors are fabricated on two polymer substrates: polyethylene terephthalate (PET) and liquid crystal polymer. Electrical resistance of the printed conductors is measured prior to deformation, as well as while being subjected to multi-directional deformation in the sculptured fixtures. Both monotonic as well as fatigue experiments have been carried out. Numerical simulations are carried out to determine strain distribution in the flexible structure as it is being subjected to these multi-directional deformations. Strain results from these simulations are compared with hand calculations and experimental data.