Direct printing methods have been used as manufacturing tools for printed electronics applications due to their cost effectiveness. In this review, the piezo-driven inkjet is discussed in detail since it is a mature technology and suitable for the production printing of printed electronics. In addition, other printing methods are considered for using higher viscosity ink and for producing smaller printed feature size. Various direct printing methods are compared in terms of jet mechanism, printing algorithm, and their applications. In particular high resolution printing methods using high viscosity inks, such as electrohydrodynamic jet, aerosol jet and micro-plotter are reviewed. To understand the recent status of industrial printing applications, display (liquid crystal display and organic light emitting diode) materials and printing issues are discussed. Finally, a brief overview of nano-particle metal based conductive inks is included because these inks have been widely used for printed electronics applications.

This study presents a new fabrication method for touch screen sensors using inexpensive, flexible, and transparent polyethylene terephthalate (PET) films. In the proposed method, a transparent capacitive touch sensor array is implemented with two independent axes of invisible electrodes consisting of indium tin oxide (ITO) patterns and bridge electrodes. A low‐cost implementation of the bridge electrodes is achieved by using near‐field electrospinning (NFES) method for the conductive lines with linewidth of 3–5 µm. Then, the printed bridge electrode is sintered using green laser without damaging the PET film. It is demonstrated that two transparent electrodes deposited on a single sheet of PET film can detect the touch location by scanning the driving signal while simultaneously measuring the capacitances from the sensing lines connected via bridge electrodes.

Electrohydrodynamic (EHD) jet printing has drawn attention due to its capability to produce smaller dots and patterns with finer lines when compared to those obtained from using conventional inkjet printing. Previous studies have suggested that drop-on-demand EHD-patterning applications should be limited to very slow printing cases with speeds far less than 10 mm s−1 due to the small dot size and limited jetting frequency. In this study, a new EHD printing method is proposed to significantly increase the line-patterning printing speed by modifying the ink and thereby changing the relic shape. The proposed method has the additional advantage of reducing the line-pattern width. The results of the experiment show that the pattern width could be reduced from 20 µm to 4 µm by increasing the printing speed from 10 mm s−1 to 50 mm s−1, respectively.

When highly insulating materials are used as substrates for electronic devices, manufacturing yields become worse, and electronic components are often damaged due to undissipated electrostatic charges on such substrates. In the case of electrospray deposition, the problem of undissipated charges is particularly vexing. If charges accumulated on the substrate are not properly compensated, a repulsive force is generated against the incoming charged droplets, which negatively affects the uniformity and deposition rate of the coating layer. In order to overcome this limitation, we demonstrated a new electrospray method, which can significantly increase the deposition efficiency even in the presence of accumulated charges on nonconductive substrates. A highly reliable superhydrophobic layer was uniformly deposited on highly insulating substrates, including printed circuit board (PCB), polyester (PET), and polyimide (PI) substrates.

Recently, inkjet-printing industry demands high-speed and single-pass printing that requires simultaneous jetting of a large number of ejectors. As a result, the jetting reliability has become an important issue in most industrial inkjet-printing applications. To ensure the jetting reliability, a real-time monitoring of the jetting status is needed. Since the monitoring process should not interrupt the printing process, the monitoring time for all of the nozzles should be less than 1 second. For this purpose, the authors developed two module prototypes to monitor the commercial inkjet heads with 1024 nozzles: (1) a head driver with an internal self-sensing capability; (2) an external monitoring module that can be used for third-party drivers. To deal with a large number of nozzles effectively, the authors are proposing a parallel sensing scheme that can be used to monitor multi-head jetting. Lastly, the authors verified our monitoring scheme by using a drop visualization system for a comparison of the monitoring results with the droplet jetting images. © 2017 Society for Imaging Science and Technology.