Flex. Print. Electron. 5 (2020) 043003 https://doi.org/10.1088/2058-8585/abc8ca Flexible and Printed Electronics OPEN ACCESS RECEIVED 13 February 2020 REVISED 26 June 2020 ACCEPTED FOR PUBLICATION 9 November 2020 PUBLISHED 15 December 2020 Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. TOPICAL REVIEW Review of digital printing technologies for electronic materials Kye-Si Kwon 1,2 , Md Khalilur Rahman 2,3 , Thanh Huy Phung 1 , Stephen D Hoath 4 , Sunho Jeong 5 and Jang Sub Kim 6 1 Department of Mechanical Engineering, Soonchunhyang University, 22, Soonchunhyang-ro, Asan city, Chungnam 31538, Republic of Korea 2 Department of Electronic Materials and Devices Engineering, Soonchunhyang University, 22, Soonchunhyang-ro, Asan city, Chungnam 31538, Republic of Korea 3 Department of Physics, Comilla University, Cumilla 3506, Bangladesh 4 Emeritus Fellow, Wolfson College, Cambridge, United Kingdom 5 Department of Advanced Materials Engineering for Information and Electronics, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, Republic of Korea 6 School of Electronics and Electrical Engineering, DanKook University, Yongin, 16890, Republic of Korea E-mail: kskwon@sch.ac.kr Keywords: inkjet printing technology, inkjet print-head, printing method, jet dispenser, display applications, conductive ink, printed electronics Abstract 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. 1. Introduction Digital printing technologies use bitmap images or computer-generated patterns to deposit ink onto tar- get substrates, and digital printing has been widely used for decades for printing graphics and docu- ments. The recent developments in printing tech- nologies are mainly related to production print- ing through the implementation of low cost, fast (high frequency jetting) and high-resolution meth- ods. Along with recent advances, there has been a lot of effort to use digital printing for direct deposition of functional materials. Direct printing technologies can have advantages over conventional photolithographic manufacturing processes, since the associated manu- facturing costs can be significantly reduced due to its additive manufacturing features [1–3]. Even though the same printing technology could be used for dif- ferent purposes, the requirements are quite different in terms of print-heads, inks and printing algorithms for use in different applications. In this review, we will assess the nozzle-based printing technologies for printed electronics applications. Throughout this paper, five key printing components will be discussed, including: (a) dispensing head, (b) printing equip- ment, (c) substrate, (d) pre (post) process and (e) functional ink. Among various printing technologies, the inkjet printing method has been a main interest to industry because it can easily be scaled up for mass production [2]. The inkjet print-head has high throughput cap- ability [4] because thousands of high-density nozzles designed into modern print-heads that can be used for printing. The number of nozzles used for print- ing can be increased further by the array layout of inkjet print-heads. High throughput features of inkjet technology were developed for graphics printing first. These features are now being adapted for printed elec- tronics applications. So, it is worthwhile to review recent advances in inkjet printing technologies for © 2020 The Author(s). Published by IOP Publishing Ltd