One of the most exciting entrants in the field is a class of inks based on graphene.
By Sanjay Monie
Printed electronics have come a long way from printed circuit boards (PCBs) that used copper containing thick-film pastes on rigid substrates, which were patterned using a two-step masking and etching process. This process resulted in a surfeit of waste and was expensive due to labor-intensive processing of the final device. By contrast, conductive inks are now available that use existing printing technologies such as screen, gravure, flexographic, offset, and inkjet to print conductive traces directly onto rigid and flexible substrates relatively cheaply. Much of the impetus for advancements in conductive inks has come from the field of organic electronics, where the promise of fully printed electronic devices and displays requires printable conductors for contacts and signal bus lines.
Printed electronics is experiencing explosive growth, as it provides the microelectronics industry a low-cost fabrication route compared to etched circuits for consumer electronics and similar applications. At the same time, it represents a high-value opportunity for the printing industry during a period of decline in print media created by the advent of electronic media. In fact, it allows the printing industry to continue to play a role in these emerging technologies, such as electronic book readers, by printing functional components onto flexible substrates.
The process of printing conductive ink is used to produce active and passive components such as transistors, resistors, capacitors, diodes, and even complete circuits such as RFID tags, keypads, sensors, and electrodes, as well as backplanes of organic light-emitting diodes (OLEDs) and other electroluminescent displays. End-use applications for printed electronics include medical devices, photovoltaics, smart packaging, flexible displays, RFID labels, energy storage, and active clothing.
In general, printed electronic circuits have lower performance characteristics and lifetimes than etched circuits, but they also have a significantly lower cost. However, they still remain too expensive for many applications. This is one of the main limitations of conductive inks, as the best performing inks based on silver nanoparticles are too expensive, while for many applications, lower cost alternatives are either insufficiently conductive (such as conductive polymeric inks), or lack in flexibility or handling characteristics (such as traditional carbon inks). One new entrant in the field of conductive inks is graphene, which could revolutionize the field of conductive inks by providing a high-performance, low-cost solution for many applications (Figure 1).
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