Discovered fundamental component that will allow control of screens without touch
In Minority Report, Tom Cruise’s character wears gloves that allow him to control the screen as if it were a touch screen, except that he touches nothing, moving his hands in the air.
This technology still gets better positioned on the side of science fiction, but perhaps not so far removed from reality.
Japanese researchers have discovered a phenomenon called the photodiode effect, which could allow the production of “touch screens without touch” – screens controlled by laser, with movement in the air.
Light Controlled Capacitor
Many advanced components for logic circuits have been developed in recent years. Instead of the electricity that controls their traditional electronic equivalents, these basic components are controlled with light – they are photoresistors, photodiodes, and phototransistors.
However, there is no photocapacitor yet.
A photocapacitor provides a new way to operate electronic circuits with light. It will drive the evolution of electronics to the next generation of photoelectronics,” said Professor Hiroki Taniguchi of the University of Nagoya.
Capacitors are basic components for all types of electronics, functioning similarly to deposits for electrons. They can, for example, store energy or filter out unwanted frequencies. A capacitor, in its simplest version, is a dielectric, made by two parallel conductive plates separated by electrically insulating material, such as air or glass. Applying a voltage to the plates causes the opposing charges to accumulate on both plates.
The properties of the dielectric play a determining role in the profile of the electric field between the plates and how much energy the capacitor can store.
The ace in the hole of a photocapacitor consists of the possibility of using light to control a property of the dielectric called permissiveness, a measure that indicates how much electrical charge is stored in a material for a given electric field, and is an indicator of the effectiveness of the dielectric material.
Other teams had already obtained a type of photodietric effect using a variety of materials, but always depending on photoconductivity, in which light controls the electrical conductivity of the materials. Increased conductance results in greater dielectric permissiveness.
But this extrinsic, or indirect, photodietric effect is not suitable for practical applications because a capacitor must be a good insulator, preventing the electric current from flowing, explains Taniguchi. But under the extrinsic photodietric effect, the insulating properties of a capacitor deteriorate. Also, this capacitor would only work with low-frequency alternating current, while the electronic circuits run on direct current.
Now, Taniguchi and his colleagues have identified an intrinsic photodietric effect in ceramic. “We demonstrated the existence of the photodietric effect experimentally,” he said.
It is not yet clear how the intrinsic photodietric effect works, but Taniguchi suspects defects in the crystalline structure of the ceramics where he was identified, whose chemical formula is LaAl0.99Zn0,01O3-? – it is worth remembering that all electronics operate by “defects” intentionally inserted into semiconductors, so-called dopant materials.
So further research will be needed before we see light-controlled screens off the big screen, but this discovery is a significant step in that direction.
Further research will seek to increase the intensity of the effect and minimize any energy dissipation. Understanding the operation of the intrinsic photodielotrico will also be possible to identify it in other materials that may be more suitable for practical applications.
Sources: Optical control of dielectric permittivity in LaAl0.99Zn0.01O3-
Takayuki Nagai, Hidefumi Takahashi, Ryuji Okazaki, Kenji Tanabe, Ichiro Terasaki, Hiroki Taniguchi
Applied Physics Letters
Vol.: 110, Issue 17