Smart screws secure critical infrastructure and radio status

If the Toyota bZ4X had the smart bolts, there would not have been the new recall. Researchers at the Fraunhofer Cluster of Excellence Cognitive Internet Technologies CCIT have developed technology to secure connections on critical infrastructure. The smart screws even warn when they are in danger of coming loose.

Intelligent screws with data transmission via radio

Screws are commonly regarded as a secure connection option. After all, we find them almost everywhere: from cranes and wind turbines to PC monitors and peripherals. However, wear and tear and other influences such as temperature fluctuations or vibrations can cause the screws to loosen or come off completely at some point. This can sometimes have fatal consequences (*cough* Toyota *cough*).

A team of researchers from the Fraunhofer Cluster of Excellence Cognitive Internet Technologies (CCIT) may now have the solution. That’s because together they have developed a smart screw connection that not only allows the connection to be monitored remotely, but also operates self-sufficiently in terms of energy.

The smart screw is fitted with a washer that has a piezoresistive DiaForce thin film. This, in turn, has a sensor system that reacts to pressure and registers the preload force generated when the screw is tightened at three points.

“When a screw loosens, the resulting change in resistance is reported to a radio module that sits on the screw head. The radio module in turn sends the data to a base station, which collects the info from all relevant screws on the object in question, explains Dr. Peter Spies, project manager and group leader of Integrated Power Supplies at the Fraunhofer Institute for Integrated Circuits IIS.

Data transmission via mioty radio protocol

While the DiaForce layer was developed by the Fraunhofer Institute for Surface Engineering and Thin Films IST, Fraunhofer IIS contributed the mioty (Low Power Wide Area Network – LPWAN) radio protocol.

Thanks to this technology it is possible to transmit small amounts of data over long distances with the lowest possible energy consumption. Several hundred thousand sensors transmit their data to a single base station, which may even be located several hundred meters or even several kilometers away.

Software then provides a graphical overview of all the intelligent screws and their status. The monitoring can be configured relatively freely and transmits the status of the bolted connections either permanently, event-based or at defined intervals.

The developed intelligent screw connections can be used in various application areas. “Regardless of whether for flange connections in industry, the bolts in steel girders on high-rise buildings, the load-bearing parts of bridges or the fastening of rotors on wind turbines – for each scenario, the system can be individually configured and adapted to the respective load profile,” writes in the press release.

The entire system also uses the energy harvesting principle. Heat and light energy are used to generate electricity. Even the minimal temperature differences between the screw head and the environment are sufficient, he said. Likewise, it is possible to generate electricity through solar cells, which makes the system energy self-sufficient, he said.

Encryption and protection

The researchers have also thought about the security of the smart screws. During the installation process, all individual screws, including the sensor unit and radio module, are placed in a tap-proof commissioning box and encrypted via RFID.

The radio link between the screw and the base station is also encrypted. “This prevents criminals or hackers from sabotaging the system. The technical personnel who monitor a wind turbine, for example, can really rely on the data,” explains Spies.

The smart screw technology has been designed for all commercially available DIN screws. Initially in screws of size M18, but soon there will also be variations for M20 and M36.