Sensor for Measuring the Moisture Content is worth Gold

While new buildings are springing up at every step, inventive researchers from the Faculty of Technical Sciences in Novi Sad are developing a unique sensor that will increase the lifespan of these buildings. This sensor measures the concentration of water in the building materials, thus providing a number of advantages such as lowering maintenance costs, improving their efficiency and durability.

There is a need for monitoring a large number of parameters in the construction industry and one of the most important ones is the moisture content i.e. the concentration of water in the building materials. This parameter should be monitored because high moisture content has a very negative effect and causes the deterioration of buildings. Continuous monitoring of moisture content in the building materials and buildings allows efficient control, timely repair and maintenance of facilities.

This was the starting point for the researchers from the Faculty of Technical Sciences in Novi Sad, led by the professor Goran Stojanović, which have developed an entirely new and unique solution in the form of a sensor. The sensor can be incorporated into the walls of buildings (during the construction and also after the construction) and is used for measuring the water concentration in them. Researchers from Novi Sad have successfully conducted the first tests on bricks and autoclaved aerated concrete blocks as commonly used materials and thus have confirmed the effectiveness of their product. The developed sensor is based on the application of Low Temperature Co-fired Ceramics (LTCC) technology, resulting in a product with high reliability and stability.

This unique sensor has been developed within a EUREKA project “New Generation of 3D Integrated Passive Components and Microsystems in LTCC Technology”, headed by Prof. Stojanović. The LTCC sensor was presented at one of the largest conferences for innovations and innovative technologies – ARCHIMEDES, which took place in Moscow, in April of 2011. The LTCC sensor was awarded the goal medal at this conference. Professor Stojanović’s research group saw this award as an additional encouragement to develop a portable (hand-held) measuring device which will communicate with the sensor, read out/show the percentage of moisture on the display, so that the sensor could fully find its use in the construction industry.

LTCC technology, construction and advantages of new sensors

The LTCC technology is a way of producing multi-layer microelectronic components and devices, whereby the layers are laminated in a device by heating to a temperature less than 1000°C, in only one step. The secret of the developed sensor actually lies in the application of LTCC technology, which involves the stacking of dielectric and conductive layers of the sensor. The outcome is a compact device characterized by low production costs and with very good electrical and mechanical properties, high reliability and stability.

The sensor consists of a dielectric layer as a substrate, while the inductor (L) and interdigitated capacitor (C) are placed in the middle, in the form of a metal layer. Furthermore, the entire structure is covered with another dielectric layer. A hole is made in the upper dielectric layer and it’s located just above the capacitor electrodes, so only these are exposed to the moisture. Humidity changes the dielectric constant of the capacitor i.e. its total capacitance which, therefore, changes the resonant frequency of the sensor. Change of the water concentration in the sample is measured wirelessly, by following changes in the resonant frequency of the sensor.

“Smart” design of the inductor (a single metal layer) provides excellent adhesion of the entire sensor to the tested construction material, which is one of the most important advantages over the so far developed similar, printed circuit board sensors. This sensor can be incorporated into the building materials, through a small incision (up to 5 cm) even in the already constructed walls. The passive nature of the sensor provides long-term monitoring of the moisture content without limitations such as battery life. Therefore, once it’s built-in, it will perform its function unlimitedly and effectively. Overall characteristics make it unique; with the development of the supporting portable device, not only will the sensor detect the change in resonant frequency and read the percentage of the moisture, but it will also be able to identify a critical concentration of water in the walls before it becomes visible. Undoubtedly, the renovation of a building is much easier at an early stage; it’s cheaper and above all, executed at just the right time, so the lifespan of the building is significantly expanded.

“Our sensor represents a completely new product in the world market and we are planning to further improve it, since it possesses a great deal of potential. We want to develop new forms of inductive and capacitive sensor components and also start producing the sensor on flexible substrates (such as foils). This would give the sensor the flexibility it needs in order to wrap it around curved structures, such as pipes and concrete supporting pillars. The flexibility of the sensor would help us avoid even the most minimal cutting of the materials,” says prof. Stojanović.


Source: www.inovacionifond.rs