The Gorilla Glass coating used as a coating on touch screens of smartphones will soon acquire some additional functions. The company Corning International, which produces this material, together with researchers from the Polytechnic University of Montreal, created a new type of material for covering touch screens, in the structure of which transparent sensors are embedded. Thanks to this coating your smartphone screen can soon be used to measure ambient temperature, your body temperature, the rhythm of your heartbeat, relative humidity and many other quantities.
Using lasers, the researchers carved photonic waveguides into the volume of ordinary Gorilla Glass, arranged at different levels relative to the top plane. Each of these waveguides acts as a kind of tunnel through which photons of light can move, similar to the movement of electrons on metal conductors.
Using different configurations of waveguides, researchers have been able to create sensors for various physical quantities. For example, a temperature sensor consists of straight and curved sections of waveguides. When temperature changes cause the glass to expand or contract, the length and shape of the two waveguide sections change slightly, which leads to changes in the geometry of the path along which photons travel. By analyzing the changes in the total flux of photons through the straight and curved waveguide, the temperature of the environment or the temperature of the object that has come into contact with the glass can be calculated with a fairly high accuracy.
In addition to providing the user with all sorts of useful information, this technology can be used for more serious purposes. With its help, it is possible to identify the identity of the user, to equip the smartphone with a unique tag and other things that can be useful in the search for a lost or stolen smartphone and in carrying out financial transactions.
Unique tags would be produced by laser-cut holes at various points in the waveguide. The combination of hole positions is unique to each piece of smartphone, and to verify such a hidden identifier, one would only need to hold the smartphone screen up to the lens of an infrared camera, obtain and analyze the image of light scattered by the holes. By comparing the image obtained with the image stored in the smartphone’s memory or in a special database, one can judge the authenticity of the smartphone or the authorization to conduct financial and other critical operations with it.
It should be noted that this is far from the first time researchers have experimented with optical waveguides. It is, however, the first time it has been done on Gorilla Glass, the most common material used to coat smartphone screens. The laser engraving and cutting method used is cheaper and simpler than the lithographic methods previously used to produce waveguides of different shapes and depths. In addition, the laser method allows to produce a waveguide at any depth in the volume of the material without affecting its surface, which makes it possible to place several sensors at once in the form of a vertical stack, one on top of another, on the same area of the display.
In addition to mobile devices and consumer electronics, this technology can find a lot of applications in other areas, for example, in medical devices, in access control systems, in security systems, etc.
