Mapping drift in morphology and electrical performance in aerosol jet printing

Aerosol jet printing (AJP) is a promising additive manufacturing technique for precise customization of sophisticated, electrically functional devices. However, the vast parameter space and variability in AJP processing present significant challenges to achieving consistent print morphologies with the requisite electrical performance. Moreover, the ability to robustly predict optimal operational windows to print suitable components is lacking. To address these key barriers, it is necessary to analyze the effect of system-level drift on the printed morphology and electrical performance in AJP processing. The temporal dependence in morphology and electrical performance of an Ag nanoparticle-based ink was evaluated over a 16-h print time, under fixed sheath and carrier gas flow rates. Qualitative shifts in print morphology over time were characterized by two critical transitions: (1) a transition from initially sparse and discontinuous to a fine and continuous morphology, and then (2) a transition from fine and continuous morphology to a coarse and continuous regime. The printed line cross-sections were height-profiled using confocal microscopy and fit to a characteristic Gaussian shape to create a statistical distribution of morphology over time. Using Monte Carlo sampling, cross-sections from the distribution were randomly paired to simulate an interdigitated capacitor (IDC) in a 2D finite element model. The computational workflow provided insights into the morphology-related mechanisms of failure in electrical performance and the consistency of morphology required for the electrical performance of the targeted IDC device. Collectively, this work highlights the inter-correlated parameter space that manifests as drift, as well as establishes a computational workflow to predict line quality and electrical performance as a function of time.