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Sheet of electronics: Printing memory on paper

Posted: 19 Nov 2014 ?? ?Print Version ?Bookmark and Share

Keywords:paper? printed electronics? memory? Andrew Steckl?

Forget plastic, glass and silicon, because soon enough paper could be the next best option as a surface for memory. While major memory vendors are breaking their backs to make improvements on manufacturing process, several researchers are focusing its efforts on a work that is in a different league altogetherexploring the potential of paper as flexible material for printed electronics.

This research is being conducted on a number of fronts. As Andrew Steckl, a professor of electrical engineering at the University of Cincinnati and IEEE fellow wrote in IEEE Spectrum, paper has a lot of potential indeed in printed electronics.

In a recent interview with EE Times, Steckl, who is started doing research with paper in 2008 at the University of Cincinnati, said paper has a lot of advantages when compared to the traditional surfaces used for printing circuits such as plastic, glass, or silicon. It's biodegradable, low-cost, and derived from a renewable resource, he noted. It's also lightweight and flexible.

Andrew Steckl

Steckl: The characteristics of the paper need to meet the requirements of the application and the properties of substrates are important.

There are so many kinds of paper available, Steckl said. "The great variety of different types of paper is astonishing." It's important to note, he added, that paper is not strictly cellulose, although it is the common element. There are always additional ingredients to make paper smoother, wider, or more robust. It could even be transparent. The characteristics of the paper need to meet the requirements of the application, said Steckl, and the properties of substrates are important. Smoothness is required for display devices, for example.

Research on paper electronics goes back as far as the 1960s, when a group at Westinghouse experimented with paper as a substrate for thin-film transistors that could be built into switching arrays to control individual pixels in a liquid-crystal display. Steckl said there are many applications and use cases for using paper, including solar cells, LEDs and other display devices, such as advertising signage.

Basic circuit components, such as wires, resistors, capacitors, transistors and diodes have all been printed on paper. But what about memory?

Steckl's work hasn't specifically looked at the potential for memory to be printed on paper, but a team of researchers at National Taipei University has published its experience using a combination of inkjet and screen printing to make small resistive RAM memory cells on paper.

University of Taipei graduate student Der-Hsien Lien, a member of the research group, told IEEE Spectrum earlier this year they were able to create memory cells as small as 50?m that could potentially be packed together to store about 1,000 bits per centimeter, which is the equivalent of 1MB on a single side of a sheet of standard A4 paper. However, the team postulates better inkjet printers with submicrometer printing capabilities could increase that memory capacity to 1GB. (Read full story here: Inkjet printing yields paper-based RRAM)

According to the group's research published in August, what the team has dubbed printed-paper-based memory devices (PPMDs) exhibit reproducible switching endurance, reliable retention, a tunable memory window, and the capability to operate under extreme bending conditions. A PPMD can be used as a labelled on electronics or living things for multi-functional, wearable, on-skin, and biocompatible applications, according to the paper. The disposability and the high-security data storage of the paper-based memory, which the researchers said are not achievable for regular silicon-based electronic devices, are also demonstrated to show the ease of data handling.

The researchers believe the all-printing approach could make manufacturing PPMDs both cost-effective and time efficient, and would be a key electronic component to activate a paper-based circuit fully. In terms of applications, PPMDs could be directly implemented in medical biosensors, multi-functional devices, and self-powered systems.

While newspapers die out as people consume information digitally, the potential to print circuits and memory on paper indicates we're still far away from being a paperless society.

- Gary Hilson
??EE Times

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