A limitation of today's ultrasound devices is that they are difficult to use on objects that don't have perfectly flat surfaces. Conventional ultrasound probes have flat and rigid bases, which can't maintain good contact when scanning across curved, wavy, angled, and other irregular surfaces.
Elbows, corners, and other structural details are the most critical areas in terms of failure — they are high stress areas. Conventional rigid, flat probes cannot image internal imperfections inside these areas.
In addition, gel, oil, or water is typically used to create better contact between the probe and the surface of the object it's examining. But too much of these substances can filter some of the signals. Conventional ultrasound probes are also bulky, making them impractical for inspecting hard-to-access parts.
A stretchable, flexible patch was developed that could make it easier to perform ultrasound imaging on odd-shaped structures such as engine parts, turbines, reactor pipe elbows, and railroad tracks — objects that are difficult to examine using conventional ultrasound equipment.
The probe is a thin patch of silicone elastomer patterned with an “island-bridge” structure — essentially an array of small electronic parts (islands) each connected by spring-like structures (bridges). The islands contain electrodes and devices called piezoelectric transducers that produce ultrasound waves when electricity passes through them. The bridges are spring-shaped copper wires that can stretch and bend, allowing the patch to conform to non-planar surfaces without compromising its electronic functions.
The device was tested on an aluminum block with a wavy surface. The block contained defects 2 to 6 centimeters beneath the surface. The probe was placed at various spots on the wavy surface, data was collected, and the images reconstructed using a customized data processing algorithm. The probe was able to image the 2-millimeter-wide holes and cracks inside the block.
The device does not yet provide realtime imaging, and needs to be connected to a power source and a computer to process data. In the future, both power and a data processing function will be integrated into the soft ultrasound probe to enable wireless, real-time imaging and video.