Sep 10, 2009
Carbon nanotube ink writes RF devices on paper
Researchers from Romania and France are investigating whether tunable resistors, capacitors or inductors can be printed using inkjet technology on normal office paper designed for laserjet printing. Paper was chosen as a substrate because it behaves as a dielectric up to 3 GHz and is the cheapest flexible organic substrate.
Tunable electronic devices are essential for any RF device, including the group's concept of a radio on paper for use as a wireless tag or an environmental sensor.
Testing the idea
The researchers' initial findings are encouraging. Their study, published in the journal Nanotechnology , demonstrates that simple, tunable, high-frequency devices (up to 100 MHz and beyond) can be fabricated by printing on paper using carbon nanotube inks containing various concentrations of double-walled carbon nanotubes functionalized to make the material soluble in water.
Inks with various concentrations of nanotubes were labelled with the letters A through to F. Then, with the help of a pipette, drops of each solution were deposited on normal paper to give similar sized (7 mm in diameter) disk-like patterns of ink. After the water is evaporated from the paper, the nanotubes remain steadily imprinted on substrate.
By measuring the impedance of the various ink disks, the scientists found that the resistance and reactance (either capacitive or inductive) of the printed component varied strongly with the applied voltage. Given the result, a radio on normal paper can be imagined with different inks functioning as a detector and a filter.
Taking this work into account together with other research dedicated to printed transistors, sensors and other circuits, a new Gutenberg revolution is envisaged for electronics, devoted to printing devices and circuits on flexible substrates, including normal paper.
About the authors
The work was performed by Dr Mircea Dragoman - a senior scientist at the National Research and Development Institute in Microtechnologies in Bucharest, Romania, Prof. Robert Plana from CNRS LAAS Toulouse, France, Prof. Emmanuel Flahaut from Université Paul Sabatier, Toulouse, and Prof. Daniela Dragoman from University of Bucharest, Physics Faculty, Romania.