Does That Bridge Look Screwed Up?

They may not be all the rage in the conversations happening in today’s technology hubs, but without the humble screw, modern machines and infrastructure would quite literally fall apart. From bridges to wind turbines, high-rise buildings, cranes, and machines of all sorts, screws make critical connections between components. Over time, these connections can weaken, or even fail, by loosening that occurs from small, repetitive movements and normal temperature fluctuations. For this reason, safety-critical structures (e.g. bridges, buildings, amusement park rides) require regular inspections by trained professionals. Such inspections are, as one might expect, expensive and time-consuming. Worse, they are sometimes neglected, which can lead to life-threatening states of disrepair.

If you find this current state of affairs to be a bit screwed up, you are not alone. Researchers at the Fraunhofer Institute for Integrated Circuits have developed a tech-laden smart screw that can let you know when it has started to become loosened. Each screw effectively continually inspects itself, and maintenance can then be targeted to actual problems when they arise.

Each smart screw is paired with a washer that is coated in a thin, piezoresistive film that generates an electrical resistance when force is applied. When the screw is initially tightened down, pressure sensors in the head register that force at three points. Should future measurements show that the forces have decreased, it is an indicator that the screw has started to come loose. Data packets would then be sent over the MIoTy low-power wide-area network protocol to a base station that could be up to several miles away to request maintenance. As many as 100,000 smart screws can communicate with a single base station.

I suppose you would not want to be the poor sap that has to go out and change the batteries in 100,000 smart screws though, right? Well, no one would, and that would just trade one maintenance issue for another, so the researchers developed a method to self-power the screws. Each screw is capable of harvesting energy from the environment by using the temperature differential that exists between the head of the screw and the ambient air temperature. That does not generate a lot of electricity, but with the screw requiring so little power to operate, it is sufficient to keep them running indefinitely.

Both wireless programming of the smart screws, and communications with the base station are encrypted to prevent hackers from sabotaging the system. This will, in theory, prevent bad actors from either masking real issues, or spinning up maintenance crews on a perpetual wild goose chase.

One point that is not specifically addressed is how a large number of screws are managed from an inventory perspective. For example, if a bridge has 50,000 screws, and one particular screw sends a report that it needs to be tightened, how would a maintenance worker locate that screw on the actual structure? That question remains to be answered, but in any case, the potential of this invention to keep infrastructure safe, and machines running, is clear. At present, M18 screws are ready for use, with M20 and M36 screws promised to be available in the near future.