Giant inductance discovered in 3D-printed carbon-black-filled polymer and its effectiveness for infill-angle self-sensing

The first report of the inductance of a 3D-printed material is provided. Giant inductance is discovered in coil-less 3D-printed (fused-deposition-modeling additive manufacturing) carbon-black-filled (30 wt%) polylactide. The ratio of the measured inductance to dimension-based calculated inductance reaches unprecedentedly high values (1250–3,970, increasing with the infill angle). The internal structure (carbon black microstructure and infill-angle-related undulation) contributes to 100% of the inductance, which increases with increasing infill angle from 0° to 90°, reaching 0.39 mH, such that the fractional increase (relative to 0°) is 90% and 220% for 45° and 90°, respectively. This increase is attributed to the current path undulation when the infill angle exceeds 0°. Thus, inductance-based infill-angle self-sensing is enabled. The fractional contribution of the carbon black microstructure to the inductance is 1.00, 0.54 and 0.33 at 0°, 45° and 90°, respectively. The resistance increases with the infill angle less significantly, with the fractional increase (relative to the 0° value) 60% and 115% for 45° and 90°, respectively. Hence, resistance-based infill-angle sensing is less effective, due to its lower sensitivity to current path tortuosity. The impedance is vastly dominated by the resistance rather than the reactance, which is totally inductive. Even at 0° infill angle (with the undulation), the inductance is high (0.13 mH), due to the branching nanostructure of the interconnected carbon nanoparticles in the carbon black. The electrical behavior is affected by the printing process only slightly, unless the infill angle exceeds 0°. Each 7-printed-layer specimen is 1.4-mm thick. The inter-electrode distance is 100 mm.