Plastic electronics represent a new range of electronics whose main aim is the production of devices on plastic substrates from organic and hybrid materials. This new technology will help in the development of lighter, more flexible devices, making it easier for them to be inserted in certain articles or even allowing the development of devices that coil up or fold on themselves.
The experimental development of these devices is the aim of the consortium members of the PLASeTOY project, which is made up of AIJU, CIDETEC (Electrochemical Technologies Centre) and CETEMMSA. This programme, supported by the Spanish Science and Innovation Ministry, is being coordinated by AIJU, the technological institute for toys.
The plastic electronic devices to be developed in this project can be split into electro-optical devices, flexible tactile devices and flexible plastic electronic tracks.
Polymer Dispersed Liquid Crystals (PDLC)
The technology called “Polymer Dispersed Liquid Crystals” or PDLC, is based on the dispersion of micro drops of liquid crystal in a polymeric matrix. The difference between the refraction rates of liquid crystal and the polymer causes a high light dispersion (Scattering) that makes the material take on a translucent aspect. When a film of this kind of material is deposited between two transparent electrodes and a field of alternating current is applied, the aspect changes from translucent (OFF) to transparent (ON) as the orientation of liquid crystal molecules is parallel to the electrical field.
the applications of PDLC technology, its electro-optical characteristics make it an excellent option for the development of intelligent windows, mainly for application in the residential and automotive sectors. Another of the widest applications is as a divider or private window electrically controlled in offices, hospitals, shop windows, etc.
CIDETEC has achieved devices as bigas 5X5 cm2. Within the PLASeTOY project the development of devices working in a reverse mode has been started, that is to say, transparent in the OFF state and translucent in the ON state, modifying the composite’s composition.
Electrochromism is the term for the property that some organic and inorganic natured materials have for changing colour under the action of an electrical field in a reversible way due to a redox reaction.
This property allows these materials to be used as filter systems in the visible light area and that of IR (Infrared) decreasing the amount of light and solar radiation that passes through. This allows the use of these kinds of materials in such applications as intelligent windows or eye filters where it is important to filter both, luminosity and solar radiation. Other applications of electrochromic materials include displays and rear-view mirrors that are darkened when light falls upon them with a certain intensity avoiding the dazzling of drivers. This application is the only one being commercialized at this moment.
CIDETEC has made an important innovation in the electrochromism field simplifying the required number of layers for the functioning of an electrochromic device, passing from 7 to 5 layers.
Also the preparation of hybrid devices combining electrochromism technology and liquid crystal is being looked at. Thus, it is possible to have a prototype with four different optical effects: colourless transparent, coloured transparent, colourless translucent and coloured translucent.
Flexible tactile switching and flexible circuits
These techniques aim to contribute new manufacturing methods which will bring a revolution in the electronic and micro-electronic industry. Basically they consist of using and adapting traditional technologies employed in graphic arts like silk-screen printing, lithography, inkjet printing and roll-to-roll, among others, for the manufacturing of electronic devices usually developed by means of other techniques. The printing of electronic components creates a need for new chemical developments for this technology, for example, conductive inks, resistive inks, insulating inks or semi-conductor inks. Commercial inks designed to be used in “printed electronics” as well as special substrates for printing purposes are already on the market. This is a promising technology, in constant evolution which till now has had satisfactory results on the market.
The main applications of flexible electronics are: pressure sensors, flexible circuits, OLED devices, flexible memories, electroluminescent lamps, flexible batteries, electrophoretic devices, RFID tags, elastic sensors, and flexible photovoltaic panels, among others.
CETEMMSA has been able to print pressure sensors by means of inkjet technology with the functionality of an on/off switch and the printing of the required circuits for the correct working of the sensor, with the inclusion of several non-hybrid LEDs (conventional) to demonstrate that printed systems work correctly and that “printed electronics” technology has a place within the toy sector.
Electroluminescence is a phenomenon in which a material emits light when an electrical field is applied. The electroluminescent devices are of a sandwich structure type and in the interior the luminescent material is deposited.
Electroluminescence has a wide range of applications, from electronic products such as mobile phones, PDA’s, watches, toy complements, decoration, advertising, and both conventional and road signs, among others.
CETEMMSA has achieved the assembly of electroluminescent devices on a flexible plastic based substrate. These systems are deposited by means of silk-screen printing, and allow the production of devices of a high variety of sizes and designs. These devices emit different colours according to the phosphorus introduced into the system. They can emit white, blue, green and orange light, among others.
Plastic Electronics in Toys
The tools available to European enterprises to keep their market share is, invariably, their competitiveness by means of the research and development of new technologies that contribute dynamism and interactivity to the articles developed.
Plastic electronics have the potential to revitalize the economy, to generate new jobs and to contribute to public health, as they allow time and cost savings and give support to increase the functionality of diverse sectors (consumer electronics, building, the automotive sector, several lighting devices, logistics and even fashion). Manufacturers that introduce these devices into their articles, add to their products differing agents to the current market, enhancing innovation, competitiveness and sustainability in the sector.
That is why, the Technological Toy Institute (AIJU) is interested in plastic electronic technologies development, with the aim of introducing important technological innovations, further to the designs created periodically, able to contribute, in the medium term, to a big technological and competitive jump forward in relation to competing countries. During 2010 this research will be continued within this project with the aim of carrying out the established objectives.