Electrical properties of copper-loaded polymer composites

3D printing of multi-material objects enables the design of complex 3D architectures such as printed electronics and devices. The ability to detect the composition of multi-material printed inks in real time is an enabling feature in a wide range of manufacturing sectors. In this study, dielectric properties of microscale embedded metal particles in a dielectric matrix have been characterized using impedance measurements as a function of particle size, shape, volume percentage and frequency. Measurements were found to agree well with calculations based on an anisotropic Maxwell-Garnett dielectric function model. Despite the metal loading exceeding the theoretical percolation threshold, a percolation transition was not observed in the experimental results. With this data, a calibration curve can be established to correlate metal loading with impedance or capacitance, which can be used with an in situ sensor for ink composition measurements during extrusion-based 3D printing. We demonstrate how an in situ sensor can locally measure the composition of the ink, allowing greater control over the resulting properties and functionality of printed materials.

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