Graphite-based Circuitry Printed on Paper
Graphite-based circuitry is created by printing a catalyst on a sheet of paper, heating it and to convert the printed areas into conductive graphite.
A printed circuit consists of electrical conducting paths reproduced on to an insulating medium designed to interconnect various devices. The first printed circuits were developed over 50 years ago and were designed to reduce weight, save space and increase reliability of the equipment during the WWII, to do away with the previous use of terminal boards and point-to-point wiring and soldering.
Circuitry built on polymer and other organic molecules as conductive components are becoming more and more common and despite meeting many requirements; they are sensitive to heat. This makes its hard for them to be integrated into usual production of electronics, where temperatures can hit 400 degrees Celsius.
Creating the Graphite-based circuitry
Researchers at Max Planck Institute of Colloids and Interfaces in Potsdam-Golm says they have created targeted conductive structures on paper by printing a catalyst on a sheet of paper, heating it and converting the printed areas into conductive graphite using a conventional inkjet printer.
The paper based electronics are able to withstand temperatures of around 800 degrees Celsius during production in an oxygen-free environment. Additionally the paper is light and inexpensive and can even be processed into three-dimensional conductive structures. To make the paper conductive, the cellulose of the paper is converted into graphite with iron nitrate serving as the catalyst.
The sheets of paper, printed with a catalyst are heated to 800 degrees Celsius in a nitrogen atmosphere. In this heating environment, the cellulose release water until all that remains is pure carbon. Graphite and iron carbide forms in a regular form in the printed areas, and though the non-printed have carbon, it is without a regular structure and therefore less conductive.
The Max Planck Institute scientists continue to test the process of the catalytic conversion to better understand how the process occurs, and be able to control reaction more effectively. To demonstrate the actual process of the catalytic conversion, the researchers used a transmission electron microscope to observe how the catalyst went through the paper in the form of nano droplets of an iron-carbon molten mixture, leaving behind the graphite.
This demonstration was aimed at understanding what actually happens during the process in making the Graphite-based circuitry, in the hope that the scientists can better control the reaction for better application. And they claim that the graphite-based circuitry technology will not only change the production of paper electronics, but also the use of iron as catalyst in the manufacture of carbon nanotubes.