Cellulose, impregnated with a special polymer mixture, serves as a sensor for simultaneous and independent changes in temperature, pressure and humidity.
Until now, various sensors were included in the same circuit, which caused some technical problems, primarily related to the user interface. However, scientists from Linkoping University managed to combine three types of measurements in a single device. They were able to achieve this with a developed elastic polymer airgel that conducts both ions and electrons and exhibits thermoelectric properties..
To create it, researchers mix cellulose nanofibers in water with a conductive polymer, PEDOT: PSS. The resulting mixture is dried by freezing in a vacuum, after which the material acquires a spongy airgel structure, and after the addition of polysilane, it becomes elastic.
The application of an electric potential leads to a linear increase in current, characteristic of the resistor. However, as the pressure rises, the resistance of the material decreases, which makes it easier for the electrons to move..
Thermoelectric properties of the material allow temperature changes to be measured (the greater the difference between the warm and cold sides, the higher the voltage).
Humidity affects the speed at which electrons travel between sides. At zero humidity, ions do not move.
What’s new, the inventors say, is that they can distinguish the thermoelectric response of electrons from the response of ions, and analyze the electrical signal over time. This allows three parameters to be measured with just one material, in parallel and independently of each other..
Team expects that such sensors will find application in the Internet of Things, commerce, security systems, and will also help reduce the production costs of companies.
Recall that recently scientists from nine research institutes have jointly created an extremely lightweight and highly durable ceramic material that able to withstand strong heat, huge temperature fluctuations and is highly flexible.
text: Ilya Bauer, photo: Thor Balkhed
Pressure & Temperature Demo