Variation of the Electrical Conductivity of PLA-based Composites with a Hybrid of Graphene and Carbon Black During 3D Printing

In order to develop conductive-biocompatible 3D parts, poly(lactic acid) (PLA) is mixed with a hybrid of carbon black (CB, 4%) and graphene (GP, 0.1-0.5%) and the change of the particle dispersion under a flow is investigated based on rheological and electrical characterizations. In CB/PLA composite, CB aggregates are rearranged and percolation structure is disrupted under the given flow, resulting in a decrease in the modulus of the composite and lower electrical conductivity. During the 3D printing process, assemblies of CB aggregates do not remain close enough to maintain the percolation structure. When CB/PLA composite is mixed with GP, CB aggregates come into contact with GP aggregates to form percolation, maintaining a durable particle percolation against a flow and realizing electrical conductivity in 3D part. Despite the orientation effect of GP, the presence of GP enhances connectivity between the aggregates under a flow and maintains electrical percolation. A cell viability test of a 3D composite part shows good adsorption and growth of the cell due to the rough surface and biocompatibility of PLA. The addition of CB and GP to PLA improves not only the electrical properties of the 3D printing part but also enhances the cell viability.