Researchers from the Fraunhofer Cluster of Excellence Cognitive Internet Technologies CCIT recently created an intelligent self-powered screw that automatically sends alerts when it detects that it has come loose.
Structures like bridges are subject to subtle movement and repeated temperature fluctuations, no matter how tightly they were screwed in when first installed. Therefore, there is always the risk that the screws will gradually loosen. Regular inspections are therefore necessary to ensure that screws and other components do not show signs of wear, loosening or coming apart completely.
This new technology, called Smart Screw Connection, could reduce bridge maintenance and repair costs. The screws come with a pre-attached washer containing a thin film of piezoresistive material that creates electrical resistance when mechanical force is applied. As the screw is tightened, sensors in the head measure the preload force at three different points, and over time, if the screw loosens, reducing the pressure applied to the film, the change in electrical resistance can be detected and used to trigger a warning signal.
The screw head also contains a radio module that can send a wireless signal to a base station that might be located some distance away. A base station can keep tabs on over 100,000 smart screws and the data it collects is shared across the internet. Anyone on Earth could monitor the condition of a structure without the need for someone to regularly visit and check the tightness of every screw installed. This not only reduces maintenance costs, but also allows problems to be solved as soon as they are detected.
To power the new technology, researchers 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 powered up indefinitely. This is a proven technology, currently used in smart devices. The technology could work to ensure that critical infrastructure always remains safe to use.