The aim of this paper is to demonstrate a pathway for in situ real-time monitoring and closed-loop control of aerosol jet printing (AJP) process. To achieve this aim, we instrumented an Optomec AJ-300 aerosol jet printer with multiple temporal and image-based sensors. Experiments were conducted by varying the sheath gas flow rate (ShGFR) and, subsequently, the line morphology was acquired online using a CCD camera mounted coaxial to the nozzle (perpendicular to the platen). To assess the line morphology, we devised a novel digital image processing method that quantifies aspects of line morphology, such as line density, overspray, continuity, edge smoothness, etc. As a result, an optimal process window was established. Next, the underlying aerodynamic phenomena that influence the line morphology are explained based on a two dimensional computational fluid dynamics (2D-CFD) model. Thus, the image processing approach proposed in this work can be used to detect incipient process drifts, while the CFD model will be valuable to suggest the appropriate corrective action to bring the process back in control. We further validate that there is a good agreement between the online and offline results with respect to the quantified morphology of the lines.

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