In-situ monitoring of electrohydrodynamic inkjet printing via scalar diffraction for printed droplets

Abstract

Abstract Electrohydrodynamic inkjet (e-jet) printing is a technique which utilizes electrical forces to generate droplets in micro/nano scale using conductive inks. Currently, there is no procedure in place to measure the printed patterns without taking the sample away from the printer setup. Removal of the substrate from the printing stage during the e-jet printing process prevents any additional work from being performed on the sample. We investigated the application of scalar diffraction for the in-situ measurement and digital reconstruction of opaque material printed on transparent substrates. Measurement and characterization of the printed material can be achieved in-situ to alter printing condition in process for quality assurance. In order to accomplish the sample reconstruction, a digital recording of a scalar diffraction pattern in the image plane was employed in this paper with a magnification of 5× with the help of a combination of lenses. The reconstructed images were then compared to images captured by an offline high-resolution microscope. The results indicated a submicron accuracy of the feature radii and the locations of feature centers. In addition to the quantitative measurements, this method also allows for the operator to view the overall form of the printed patterns. Our findings demonstrate an effective approach for in-situ monitoring of e-jet printing and printed patterns, which could pave the way for the industrial application in printing testing field.