In-situ real-time characterization of micro-filaments for electrohydrodynamic ink-jet printing using machine vision

Abstract Electrohydrodynamic ink-jet printing (e-jet printing) is one of micro/nano scale 3D printing techniques that automatically deposit functional materials to form 3D structures on the substrate. Unlike traditional thermal or acoustic inkjet printing, e-jet printing utilizes high electrical forces that enable the ink to overcome surface tension at the tip of micro needles. The filaments/droplets coming out from the needle have dimensions much smaller than the dimensions of the nozzle, thus printing geometries in micro and nano scale. Process parameters in e-jet printing could affect the final quality attributes of fabricated constructs. Currently, assessment of these critical geometries and attributes must be performed offline using optical microscopy or scanning electron microscopy. This drawback affected the efficiency of micro/nano printing from translation into industrial practice. The research in this paper focused on fundamental research to enable in-situ monitoring of e-jet printing using a real-time image characterization technique. In conclusion, the study in this paper investigated using machine vision for real-time monitoring of micro scale 3D printing. The method worked well for characterization of micro-filaments, and may be further implemented into feedback control system of complicated e-jet printing. However, the optical machine vision was limited to micro scale detection. One of the future research topic is to develop nano scale in-situ characterization mechanism for e-jet printing.