Researchers from the Fraunhofer Cluster of Excellence Cognitive Internet Technologies CCIT recently created a smart self-powered screw that automatically sends out alerts when it detects that it has loosened.
Structures like bridges are subject to subtle movements and repeated temperature fluctuations no matter how tightly they were screwed in upon first installation. As a result, there is always the risk that screws will gradually loosen. Regular inspections are needed, therefore, to ensure screws and other components are not showing signs of wear, loosening, or becoming completely undone.
This new technology, called the Smart Screw Connection, could save costs on bridge maintenance and repair. The screws come with a pre-attached washer containing a thin film of piezoresistive material that creates an electrical resistance when a mechanical force is applied. When the screw is tightened, sensors in the head measure the preload force at three different points, and over time, if the screw comes loose, resulting in less pressure being applied to the film, the change in electrical resistance can be detected and used to trigger a warning signal.
The head of the screw also contains a radio module that can send a wireless signal to a base station that could be located some distance away. One base station could keep tabs on over 100,000 smart screws, and the data it collects shared over the internet. Anyone on Earth could monitor the status of a structure without requiring someone to regularly visit and check the tightness of every single screw installed. That not only reduces maintenance costs, but allows problems to be addressed as soon as they are detected.
In order to power the new technology, the researchers have turned to thermoelectric energy harvesting. This would allow temperature differences between the screw head and the environment around it to generate enough electricity to keep it indefinitely powered. This is a proven technology, currently used in smart devices. The technology could work to ensure that critical infrastructures always remain safe to use.