All you need is a red marker and a laser to build a sensor
Perhaps without knowing it, we keep a good number of sensors in our pockets. In the smartphone alone there is at least the accelerometer to detect movement, the gyroscope for rotation, the proximity sensor that detects the approach of our ear, the fingerprint sensor for facial identification. And the list grows longer if we also include other electronic devices for daily use: from smartwatches to laptops , not to mention all the sensors in the home for domotics. In short, we live surrounded by a sensorized world, essential for data collection.
The sensor market is expected to register a CAGR (compound annual growth rate) of 7.8% during the forecast period over the next five years , and 50% of networked devices will be IoT. This explains why a growing number of researches are focusing on sensor engineering, for the development of less expensive materials and more efficient processes. But there is not just one material for sensors – a lot depends on the type of use – even if silicon is certainly the most used in electronics. Now a very important discovery for sensors comes from Italy, which could represent a small great revolution. And it was almost by chance, as Francesco Greco, professor of bioengineering at the BioRobotics Institute of the Scuola Superiore Sant'Anna in Pisa , tells us . "A PhD student of mine, Alexander Dallinger from the University of Graz in Austria, where I was in a transition phase at the time, was doing experiments on polymeric materials, trying to convert them into graphene using a laser. By chance he marked an area to test with a red marker that, when the laser beam passed through, made a black trace appear, typical of the formation of graphene." From there, the scientific investigation began, leading to the discovery of a chemical substance, contained in the red, Eosin Y, which resists the passage of the laser, at temperatures of about 3 thousand degrees and allows the formation of a porous, non-crystalline graphene "with which to create both conductive material that sensors without chemical processes and without solvents” at very low costs, because the ink is low cost and the process does not require controlled environments or complex equipment. The laser, in fact, can be used to engrave awards or plaques and “instead of mounting circuits or sensors that are often heavy, expensive, bulky on objects, we can write them directly where needed” explains Professor Greco.
From an application point of view, circuits and sensors can be made on many surfaces such as glass, ceramics, wood, fabrics and many technological applications can be hypothesized. In the field of printable electronics , conductive inks (for example made of metal particles) are normally used to make circuits and sensors, while "with this approach you can use the printing of a very normal colored ink and then define the circuit or the graphene sensor". A particularly important field in which to locally monitor the temperature is that of computer and smartphone chips that tend to overheat and maintaining the correct temperature is essential for their operation. "Our technique allows us to make temperature sensors in a non-invasive way on the case or even directly on the chip packaging , without increasing size and weight".
Going further, it comes to mind the automotive sector . Our cars are now connected and sensors are very common not only for electronic functions, but also for mechanical components, but also parts of the bodywork or the passenger compartment where it is "necessary to introduce circuits, sensors in a minimally invasive way, avoiding assembly or wiring for the creation of environmental sensors" argues the inventor professor who patented the invention. For more everyday use , however, it would be interesting to know the temperature of our cup of coffee to enjoy the perfect moment of daily relaxation. And it will be possible, apparently with printable sensors. Instead, "for IoT applications it could be used on objects to be sensorized that are able to detect parameters and communicate thanks to the use of wireless technologies".
Meanwhile, research continues, because the intention is to extend the scope of application to develop physical and chemical sensors of temperature, deformation, pressure intended for industrial applications or for medical devices or to integrate them on robotic surfaces, especially in the pioneering field of soft robotics. To push the pedal also on sustainability, the research team of Sant'Anna in Pisa is exploring another field: the use of natural dyes obtained from vegetable or food waste with chemical structures similar to those of eosin, from which graphene was developed. To reduce the impact on the environment.
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