https://phys.org/news/2018-10-team-health-magnetostrictive-transducer.html

The circular, hard-shell MsT sensor clamps around pipes and other structures and is available in circumferences ranging from one-half inch to 70 inches. It detects material flaws, corrosion and areas at risk of developing cracks and leaks. At just 1.1 inches wide, MsT uses less shear-wave couplant, a gel that aids energy transmission, and requires less clamping force when dry coupled, meaning when no couplant is used.

The MsT sensor can be permanently installed on a structure to provide ongoing monitoring. A battery-operated hub collects and wirelessly transmits data from the sensor and can connect to multiple sensors at once. The hub can be programmed to change the sensors' frequencies automatically to meet industry safety standards, which require a structure be tested using at least two frequencies.