Adam Krajewski1

1, Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio, United States

The Graphene-Infused PLA is a material made by melt blending commonly used Polylactic acid (PLA) with a few weight percent reduced graphene oxide (r-GO) to create an electrically conductive filament for polymer additive manufacturing. Among the other possible uses, it allows printing conductive circuits inside 3D printed PLA models using dual-extrusion with no change in mechanical properties of the model and printing flexible conductive circuits on fabrics using a standard FDM printer. In the recent years there were multiple successful studies on adjusting its composition and processing methods to achieve high conductivity. However, none of the studies have investigated how this property change over time when the material is used in a working device, what can be crucial to reliability of such device.
In the course of this study, we have investigated changes in the conductivity of as-printed Graphene-Infused PLA under electrical stress conditions that could be found in the target applications. Over 60 samples of additively manufactured tracks with 1.26mm x 4mm cross-section and 90±5μm layer height were prepared on non-conductive PLA substrate using popular Ultimaker 2+ FDM printer. Samples were studied in two separate experimental setups. In the first one, 36 samples underwent long-term study in which they were placed in groups, with different constant potentials applied and monitored for multiple weeks. The goal was to investigate reliability, variability and performance changes that would happen over lifetime of low-power devices like wearable electronics. In the second experiment, samples underwent short-term 6 hour long tests in which conductivity was measured with higher frequency and electrical stress characteristics were varied over broader spectrum, in order to well investigate the process of conductivity change and help formulate a theory explaining it.