Simply popping a pill to identify a fault – researchers at Fraunhofer IZM have made this a reality in cooperation with Micro Systems Technologies (MST) and Sensry GmbH. As small as a piece of candy, the waterproof IoT sensor can reliably measure the properties of liquids even in hard-to-reach places. This can significantly facilitate the maintenance of industrial machinery and even help identify diseases.
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The larger an industrial machine, the more difficult it is to detect an unwanted deviation in oil pressure or even a leak in a line from the outside in the event of a malfunction. A lot of time often elapses until specialist personnel find the needle in the haystack. This results in production losses and high costs. The situation is similar when it comes to identifying the causes of illness in humans. If patients complain of pain in the abdomen, there is usually no way around a complex gastroscopy or colonoscopy. In such cases, electrochemical impedance spectroscopy can provide relief.
In this procedure, a frequency spectrum is sent from one electrode through a medium to a second electrode: From this, a spectrum, i.e. a specific fingerprint of this medium, can be derived. If changes in material or fluid properties become apparent, this can be an indication of either the progressive corrosion of a component or the presence of a certain disease. Until now, impedance analyzers have not been small and mobile enough to be used for these purposes. Researchers at the Fraunhofer Institute for Reliability and Microintegration IZM in Berlin, with support from MST and Sensry, have therefore developed a compact and modular IoT sensor for these applications that can measure impedances and transmit them wirelessly. Consequently, it is not only waterproof but also biomedically compatible.
The sensor is made of a biocompatible polymer and combines the two necessary electrodes with numerous components for analyzing environmental properties, including six sensors for measuring a wide variety of data, on just 11 x 16 square millimeters. In addition to temperature, pressure, humidity and sound in the environment, the small multi-talent can also record its own acceleration behavior, rotation or ambient noise. Light and colors can be determined by an integrated light sensor.
In concrete terms, if a machine malfunctions, for example, you enter the sensor into an oil line and it then flows through the entire system. Wirelessly, accurate data about the characteristics of the environment are transmitted in real time to a specially developed software with web interface for PC and smartphone. If a location is reached where the pressure or fluid spectrum deviates from the norm, this is an indication that the cause of the problem has been successfully localized. For easier classification of the collected data, the spectra of some liquids, such as oil or water, are already stored in the software.
In the production of the sensor, the strong miniaturization of the components in particular posed a major challenge. In particular, reducing the coil diameter to 10 millimeters for wireless charging was a hurdle. However, a sophisticated system design made it possible to overcome this challenge. At the start of the project, Sensry GmbH provided its circuit diagrams and Kalisto firmware as the basis for developing the sensor.
To accommodate a total of more than 70 passive and active components on a flexible and biocompatible printed circuit board, it was designed from a liquid crystal polymer and manufactured in four layers by DYCONEX, an MST company. Yet it is just 175 micrometers thin, barely thicker than a human hair. A system-in-package was fabricated on a six-layer interposer and forms the core of the sensor, as that is where the IoT system is unified. For wireless charging, the capsule does not even have to be opened thanks to a built-in induction coil and can be charged wirelessly via Qi technology. However, a classic DC charging process is also possible via a docking station for calibrating and programming the sensor. To prevent the very small components from getting too hot during operation, the sensor is also filled with an epoxy resin that isolates the components from each other and dissipates the heat to the outside. At the bottom end, it terminates with a 0.5-millimeter-thin four-layer ceramic plate manufactured by Micro Systems Engineering GmbH, an MST company, on which the electrodes for impedance spectroscopy are mounted alongside the pressure sensor. As a trade show demonstrator, the IoT sensor shows how intelligent system design and semiconductor packaging can greatly miniaturize electronics without losing functionality.
Research on electrochemical impedance spectroscopy is in full swing, and the possibilities for medical technology are far from exhausted.
The project has been running since 01.04.2021.
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