Using artificial implants in surgeries to support human tissue or bone that isn’t functioning optimally anymore is commonplace. But what if those implants also could monitor on-site what’s going on inside the body and report back to physicians? That’s the promise of new custom, 3D-printed smart metamaterial implants developed by researchers at the University of Pittsburgh Swanson School of Engineering. The implants—which are called cages—can be used in spinal-fusion surgeries to provide support not only to replace the disk that was once there, but also to monitor the healing of the spine following the procedure, researchers said.

“Smart implants can provide real-time biofeedback and offer many therapeutic and diagnostic benefits,” said Amir Alavi, a Pitt assistant professor of civil and environmental engineering, whose Intelligent Structural Monitoring and Response Testing (iSMaRT) Lab led the research.

However, incorporating devices with typical bulky electrical circuits and power sources would not be possible in an area as small as the one where an implant is placed in spinal-fusion surgeries, he said.

Metamaterial as a Sensing Device

To reach their aim of developing a suitable implant, the iSMaRT Lab team focused on using “the implant matrix as an active sensing and energy harvesting medium,” Alavi said.

Key to the design of the implant is a new class of multifunctional mechanical metamaterials—or so-called “meta-tribomaterials”—of which they are made, researchers said. The materials—which are self-aware—act as their own sensors and can record and relay data about the pressure and stresses on the implant structure.

Researchers designed the material with a built-in triboelectric nanogenerator that provides it with its own power source as well as sensing capability. When put under pressure, contact-electrification occurs between the material’s conductive and dielectric microlayers, creating an electric charge that relays information about the condition of the material matrix.

“Spinal fusion cages are being widely used in spinal fusion surgeries, but they’re usually made of titanium or PEEK polymer materials (a semi-crystalline, high-performance engineering thermoplastic) with certain mechanical properties,” explained Alavi in a press statement. “The stiffness of our metamaterial interbody cages can be readily tuned.”

Custom Design

Moreover, the implant can be 3D-printed based on the patient’s specific anatomy before surgery, which makes it a more natural fit and thus increases the odds of a successful recovery, he said.

A tiny chip within the implant records data about the pressure being put on it, which is an important indicator of healing, researchers said. Medical professionals and other caretakers can read the data on the chip in a noninvasive way using a portable ultrasound scanner, they said.

Researchers published a paper on their work in the journal Advanced Functional Materials. They already have tested the device in human cadavers and next plan to see how it performs in animal models.

In addition to specific use for spinal implants, scientists also can apply the metamaterials and smart-sensor design to other medical applications, such as cardiovascular stents or components for knee or hip replacements, Alavi said.

“This technological advancement is going to play a major part in the future of implantable devices,” he said in a press statement.

Article source: MDDI