Heat and pressure can deteriorate the properties of piezoelectric materials that make state-of-the-art ultrasound and sonar technologies possible – and fixing that damage has historically required disassembling devices and exposing the materials to even higher temperatures. Now researchers have developed a technique to restore those properties at room temperature, making it easier to repair these devices – and paving the way for new ultrasound technologies.

Piezoelectric materials have many applications, including sonar technologies and devices that generate and sense ultrasound waves. But for these devices to efficiently generate sonar or ultrasound waves, the material needs to be “poled.”

That’s because the piezoelectric materials used for sonar and ultrasound applications are mostly ferroelectric. And like all ferroelectric materials, they exhibit a phenomenon called spontaneous polarization. That means they contain pairs of positively and negatively charged ions called dipoles. When a ferroelectric material is poled, that means all of its dipoles have been pulled into alignment with an external electric field. In other words, the dipoles are all oriented in the same direction, which makes their piezoelectric properties more pronounced.

Northwestern University scientists have developed a new bioactive material that successfully regenerated high-quality cartilage in the knee joints of a large-animal model.

Although it looks like a rubbery goo, the material is actually a complex network of molecular components, which work together to mimic cartilage’s natural environment in the body.

In the new study, the researchers applied the material to damaged cartilage in the animals’ knee joints. Within just six months, the researchers observed evidence of enhanced repair, including the growth of new cartilage containing the natural biopolymers (collagen II and proteoglycans), which enable pain-free mechanical resilience in joints.