Optimisation of Substrate Angles for Three Dimensional Inkjet Printing of Multi-Functional and Multi-Material Parts

Three dimensional (3D) inkjet printing of multiple materials is being explored widely to fabricate multi-functional parts such as the printing of strain gauges and heating elements embedded within a component. Although dielectrics and conductive materials can be inkjet-printed together, there is a difference in their layer thicknesses. Inkjet printed conductive materials require sintering at temperatures of around 150°C to form a conductive network. Exposing the dielectric materials which may be sensitive to prolonged heat exposure could affect their material properties. Hence, optimisation of conductive routes within the structural material is essential. It is envisaged that printing of structural materials at an angle to a certain height/layers and then printing a few layers (~ 10 layers) of conductive material on to the top surface will enable faster fabrication and reduced exposure of the dielectric material to heat. To compliment this aim, in this study, dielectric substrates were printed at different angles and the conductivity of the tracks were assessed. Surface morphology of the printed tracks showed misplacement of droplets for angles above 15° due to the influence of print height. The printed tracks remained conductive up to 65°; however above 50°, the tracks were highly resistive (> 150KΩ). The optimal angle to obtain conductive tracks with the highest print resolution was 15° and it was greatly influenced by the print height. Further study is required to optimise the substrate angle by using a constant print height and varying the slope length.Mechanical Engineerin