Analysis of formation of an individual droplet using a high-resolution multi-exposure imaging system

Localized dispensing of precious functional materials has attracted considerable interest in the academic as well as the industrial society. While the number of publications show numerous fields of applications in printed electronics, photovoltaics, display technologies and thin functional coatings, the transition into the industrial sector is often hindered by challenges resulting from ink-printhead combinations and their implications on reliability and stability of the process, as well as side-effects such as mist accumulation in heavy duty printing equipment. While measuring equipment to quantify various rheological and interfacial parameters for fluid optimization has been developed with the accompanying mathematical models, the physical jetting experiment as well as high-duty printing trials cannot yet be substituted by these methods. In order to quantify the generation of a droplet alongside with its tailing behavior and mist formation as well as statistics based on cross-talk effects and relaxation-related effects, high-resolution and high-speed imaging are required. This paper examines the optical setup and outlines the required calculations for establishing sharp, high-resolution images using a combination of a high power laser diode with a resonant ME MS micro mirror with a theoretical resolution of 1.8 pm. The limitations of the setup regarding the achievable resolution as well as potential improvements are assessed. Furthermore, the experimental setup, including repetitive generation of nanosecond-pulses necessary for motion-blur-free images, will be discussed. Additionally, results from imaging a droplet formation process using a Xaar 126 printhead are discussed.