Residual polymer stabiliser causes anisotropic conductivity in metal nanoparticle 2D and 3D printed electronics

Inkjet printing of metal nanoparticles (MNPs) allows for design flexibility, rapid processing and enables 3D printing of functional electronic devices through co-deposition of multiple materials. However, the performance of printed devices, especially their conductivity, is lower than those made by traditional manufacturing methods and is previously not fully understood. Here, we revealed that anisotropic electrical conductivity of printed MNPs is caused by organic residuals from MNPs inks. We employed a combination of electrical resistivity tests, morphological analysis and novel 3D nanoscale chemical analysis of printed devices using silver nanoparticles (AgNPs) to show that the polymer stabiliser polyvinylpyrrolidone (PVP) tends to concentrate between vertically stacked AgNPs layers as well as at dielectric/conductive interfaces. The understanding of organic residues behaviour in printed nanoparticles reveal potential new strategies to improve nanomaterial ink formulations for functional printed electronics.