The use of 3D printing technology in electronics has enabled the rapid development of passive and active circuit components, flexible wearables, and many more. However, no two print runs are alike due to a lack of optimum process control. Ink-jet technology is prevalent in printed electronics (PE) and involves nozzles injecting ink on demand. Nozzle performance is crucial for quality prints; however, it is difficult to monitor in real-time. We report on in-situ ultrasonic imaging of printed, electronic ink to characterize nozzle performance and ink quality of an ink-jet printing system. The imager consists of a 128 x 128, 50 μm pixel array of Aluminum Nitride (AlN) transducers that transmit/receive GHz frequency short ultrasonic pulses. Ink can be directly printed on the imager’s silicon surface, and ink types can be differentiated based on their acoustic impedance. The controlled firing of individual nozzles also allows for determining clogged nozzles or nozzles firing ink with air bubbles trapped. In response, poor-performing nozzles can be shut off to improve print quality. During printing, the GHz imager can be used to provide real-time quantitative feedback on the nozzle performance, thus providing uniform and higher-yield PE devices.
