Ultrasound Patch Opens New Doors in Non-Destructive Testing Methods
Rachel Maya Gallagher posted on April 04, 2018 |
Flexible island-bridge structure embedded in silicone elastomer enables probe to conform to irregula...

Imagine slapping a patch on a leaky pipe and getting a 3D image of the interior, complete with the exact location of the corroded segment, on your tablet within seconds. This sci-fi scenario could become a reality once a new ultrasound probe passes the proof-of-concept stage.

An ultrasound patch is used to image irregular surfaces without first submerging them in water. (Image courtesy of Hongjie Hu.)
An ultrasound patch is used to image irregular surfaces without first submerging them in water. (Image courtesy of Hongjie Hu.)

Until now, ultrasound probes used to inspect damaged machine parts have been rigid. Making sufficient contact to image irregularly shaped equipment was nearly impossible; an inspector assessing a damaged car engine would have to disassemble it completely and immerse every component in water to determine the source of the malfunction. Conducting ultrasonic testing on a slab of concrete required careful surface cleaning and application of a gel or liquid film to facilitate contact. Now, using ultrasound wave-producing piezoelectric transducers embedded in a thin silicone elastomer patch, researchers are able to locate defects more easily than ever before.

Island-Bridge Structure

The island-bridge structure of the ultrasound patch allows it to conform to various surfaces without sacrificing sensitivity and conductivity. The piezoelectric transducers and electrodes form “islands” connected by copper wire “bridges.” The spring shape of the copper wires allows them to expand and contract under strain without putting a significant amount of stress on the electrical components themselves. The resulting probe was able to detect 2-millimeter-wide defects inside an aluminum block after being laminated in several locations on the block’s wavy surface.

The spring shape of the copper wire “bridges” are visible in the ultrasound patch applied to a rounded surface. (Image courtesy of Hongjie Hu.)
The spring shape of the copper wire “bridges” are visible in the ultrasound patch applied to a rounded surface. (Image courtesy of Hongjie Hu.)

Past research into the ultrasonic testing involved applying electrodes to machine components after coating them in lubricant film. This method still required the use of a film to facilitate better contact between the piezoelectric transducers, making it impractical for quick assessments or imaging continuously for long periods of time. Researchers at the University of California, San Diego have bigger plans for their flexible ultrasound patch and don’t intend to confine it to mere in-house damage assessments.

Future Applications

Currently, the flexible ultrasound patch still needs to be connected to a power source to function. When applied to an aluminum block with a wavy surface, generating an image from the ultrasound reading collected required running the data through a custom algorithm. However, researcher Honjie Hu hopes to make the device sufficiently autonomous so that it can monitor defects in engines, airplane wings and suspension bridges in realtime.

The flexible ultrasound patch, here attached to the elbow of a pipe, can find flaws or blockages within the pipe without requiring the inspector to disassemble a plumbing system first. (Image courtesy of Hongjie Hu.)
The flexible ultrasound patch, here attached to the elbow of a pipe, can find flaws or blockages within the pipe without requiring the inspector to disassemble a plumbing system first. (Image courtesy of Hongjie Hu.)

To learn more about non-destructive testing methods, check out Part One and Part Two of our overview on NDT.


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