First report of the behavior of a 3D-printed material in an oblique direction off the in-plane direction

The behavior of a 3D-printed material in the oblique direction is unprecedentedly reported. The measurement is electrical. The material is electrically conductive (carbon-black-filled polylactide). This direction is off the longitudinal (in-plane) direction, by 0.80°–2.01°. Despite the small angle and the essential equality of the longitudinal and oblique distances, the inductance (also inductance per unit distance) and resistance (also resistivity) are greater in the oblique direction than longitudinal direction by 12–13%, because the oblique direction intersects the interfaces between the printed layers. The interfaces contribute ≥ 11% of the oblique inductance/resistance, while the carbon black nanostructure (nanoparticular aggregates) and the infill-angle-related undulations govern the remaining ≤ 89%. This structure promotes current path tortuosity, thereby enabling giant inductance. The interlayer interfaces further enhance the tortuosity and hence the inductance. The fractional contribution of the structure to the inductance (≥ 0.89) decreases with increasing inter-electrode distance. The ratio of the measured to dimension-based calculated inductance is ≤ 8500 and ≤ 9600 for the longitudinal and oblique directions, respectively—the highest ever reported. The high inductance (0.1-mH range) causes the electrode-specimen interface inductance to be substantial, due to the magnetic flux continuity. The high resistance (10-kΩ range) causes the electrode-specimen interface resistance to be substantial. Thus, the inductance and resistance of the electrode-specimen interface should not be ignored. The inductance complies quantitatively with the model of inductors in series, whether longitudinal or oblique, provided that the inductance of the electrode-specimen interface is deducted from the measured inductance. The resistance similarly complies with the model of resistors in series.