And so after the first article I wrote about her research, the discoveries in the fields of paper transistors and transparent electronics (together with all their practical applications), the researcher Elvira Fortunato, together with her team and her husband Rodrigo Martins (also a nanotechnology, materials and electronics researcher) is back in the headlines... for the second time. First an invitation by the Nobel Committee arrived, for them to present personally their discoveries in Stockholm before a panel of specialists.

Then a second patent was registered by the team, related with the invention of the electronic memory made of paper: for the first time ever, they could store great amounts of information for a period of 14.000 hours (one year and a half) inside celluloid cells - the record was 14 hours until now (to smaller amounts of information), and using continuous arrangements of cells, not discontinuous ones. Nothing like that had ever been done before... actually, no theory existed which could frame or predict the laboratory work they have done with the celluloid cells - in theory, it was not possible. And their target is to store much more information inside a single cell. The practical applications of such findings are vast and incredibly interesting.

And now... a third important patent was registered by the team of Elvira in late April 2009. Imagine that you want to change the colour of your house or apartment's walls, floor and ceiling, windows, doors, fridges and cookers, mobile phones, tvs and computers, cars and motorbikes or any other kind of surface - you want to change it with little effort, very frequently and to any other colour you wish, by pressing only a button or two. Well, now you can. A new transistor which changes the colour of any material instantly was invented and registered by the team. Sounds like science-fiction but it's just... nanotechnology.

The electrochromic transistor changes the colour of any surface where it is implanted. Until now, these transistors can be implanted in surfaces made of glass, paper, ceramics, tiles, metal or any polymer (plastic, rubber, polyurethane, polystyrene, etc.), have great potential if applied to screens - computer, PDA, Tv, mobile phone screens - and still advertisement surfaces as well. Better: they can be produced by... an ink jet through a common printer which had its cartridges filled with a yellowish solution which contains electrochromic nanoparticles!

Through the application of an electric tension, this material changes its oxidation state, meaning that... it changes its colour. This is the beginning of printed electronics, which interests great companies all around the world. When the material used is a sheet of paper, it is printed with the electrochromic solution and passes through the printer fifteen times.

Then the transistors are made, using paper as an insulating material (which avoids short circuits) instead of silicium, placing the door - which controls the flux of energy - on one of the surfaces and the two conductor electrodes on the other (the source, where the energy comes in, and the drain, where it goes out). 

For now, they're using 0,3 to 0,4 mm transistors in their experiments, but Rodrigo Martins advances that their size "can be much smaller, with 1 micron (a thousand part of a millimetre), something which will definitely increase the definition of the image on the screens”. This represents "a two-in-one solution: the pixel is the transistor itself, which turns its production much cheaper", Elvira explains.

The previous findings and their patents were registered under a single brand:"Paper-e: Green Electronics for the Future". "After the paper transistors, we have been going through a whole series of findings (...) to use the paper as an insulating material of the transistor is like a Columbus egg, it's a two-side photocopy, everything looks very simple, because if we change the structure of the paper, we change its functionality", Elvira declares. 

She adds: "The applications on paper are made in the optics of disposable and recyclable electronics, because paper is by far the cheapest material, so its life span interests us very little, as even the production specialists in this sector reaffirm to us". And Rodrigo finishes: "[Paper] is the lightest substract that I know". 

In February this year Samsung released on the world market a new TV screen with semiconductor oxyde technology created by Elvira & Rodrigo's team, which allowed gains of 300% in the functionality of the electronic devices. With the new electrochromic transistors, the team from Lisbon's Nova University expects a new reduction in production costs - a much cheaper and simpler process to produce photovoltaic cells with a slightly modified ink-jet printer (cartridges filled with a solution of nanoparticles of metallic oxydes) was invented.

Link with video at OpenMaterials.org:

"We can also create architectonic paint which looks like standard paint but allows us to change the way how our home looks from day to night, inks, changing tiles (...) I think that the limit will be our imagination" (Rodrigo Martins)

Photos by Expresso:
1 - Elvira, her husband and some members of their research team
2 - Piece of paper soaked in electrochromic solution
3 - An electric charge provokes the visibility of a newspaper page with the news of the finding and a photo, showing up in blue colour in this case 
4 - Modified ink-jet printer
5 - Paper-e company logo

Sources: Expresso