Electrochemical enhancement of carbon black-infused poly(lactic acid) filament for additive manufactured electronic applications

Abstract

Here we present an electrochemical method to enhance the electrical conductivity of commercially available, carbon-black infused polylactic acid (PLA) for use in material extrusion-based additive manufacturing (MEAM). After fabrication, the carbon-black infused PLA structure was processed in aqueous solutions consisting of either hydrochloric acid (HCl), nitric acid (HNO3), or sulfuric acid (H2SO4). This study examines the effects of acid concentration of the three types of acids, input waveform shape applied during the electrochemical process, waveform amplitude, and the frequency of the waveforms on the bonding of the negatively charged ions to the conductive PLA. We found that inputting a DC square pulse in a 7 M H2SO4 solution yielded a 51% reduction in electrical resistance. X-Ray diffraction (XRD) analysis shows that line width does shift to lower 2θ values without affecting the d-spacing and the 2θ peaks decay indicating that the ions introduced through the electrochemical doping process are being diffused into the conductive workpiece. Energy dispersive X-ray spectroscopy (EDS) showed the presence of sulfur ions located throughout the processed carbon-infused PLA, even at the core. Throughout this study, we found that this electrochemical process can create electrically in-active dead zones that occurs from higher current densities. XRD analysis reveals that peaks in these dead zones move to higher 2θ, rather than lower 2θ in the improved areas. This points to a shrinking of the lattice structure and verifies that structural changes are occurring. Electrically improved areas can be utilized in conjunction with electrically in-active dead zones to create conductive areas with insulating zones, mimicking copper traces on a PCB. This electrochemical process provides the opportunity for fused filament fabrication to be used in more electrical applications.