Electro-mechanical Property of 3D Printed Cubic Structure Using Carbon Materials/Thermoplastic Polyurethane Filament with Various Infill Patterns

This study aimed to confirm the most suitable materials and 3D printing processing conditions as infill patterns to fabricate 3D-printed soft conductive structure using fused filament fabrication (FFF) 3D printing. The samples were fabricated into cubic structures using two types of carbon materials/thermoplastic polyurethane (TPU) filament, graphene (GR)/TPU, and carbon black (CB)/TPU. The 3D printing processing conditions were set as follows: nozzle size of 0.4 mm, nozzle temperature of 250 °C, printing speed of 60 mm/sec, and infill density of 20%. Especially, infill patterns set as Zigzag (ZG), Triangles (TR), and Honeycomb (HN). Characteristics were analyzed through actual printing time and weight, compressive property, electrical property, and electromechanical property. The electromechanical property was evaluated by checking conductivity during repeated compression to verify the piezoelectric characteristics. As results, printing time was longest for HN, followed by TR and ZG, while CB/TPU structures were heavier than GR/TPU ones. Compressive stress was twice as high for GR/TPU compared to CB/TPU, with HN exhibiting the highest strength among infill patterns. Electrical conductivity was superior in CB/TPU structures, particularly with the HN pattern. Moreover, CB/TPU demonstrated higher conductivity during repeated compression, with the HN pattern showing optimal characteristics due to minimized layer spacing. Thus, CB/TPU with its superior elasticity and conductivity, combined with the HN infill pattern, was deemed suitable for conductive structures.