Spinal fusion, fusing two vertebrae together, can treat a wide variety of spinal disorders. Surgeons will often use a cage to provide support where the disc used to be between the vertebrae. But what if these cages could withstand the healing of the spine in more ways than one?
Researchers at Swanson University of Pittsburgh School of Engineering are creating 3D-printed smart metamaterial implants specific to patients that act as sensors to monitor spine healing. An article detailing his work was recently published in the journal Advanced Functional Materials.
“Smart implants can provide real-time biofeedback and offer many therapeutic and diagnostic benefits,” said Amir Alavi, assistant professor of civil and environmental engineering, whose iSMaRT lab led the research. “But it is very difficult to integrate bulky circuits or power supplies into the small implant area. The solution is to use the implant matrix as an active means of energy detection and collection. We have focused on this.”
The iSMaRT (Intelligent Structural Monitoring and Response Testing) laboratory has developed a new class of multifunctional mechanical metamaterials, which act as their own sensors, recording and transmitting important information about pressure and stresses to their structure. So-called “meta-tribomaterials,” also known as self-conscious metamaterials, generate their own power and can be used for a wide range of detection and monitoring applications.
The material is designed so that under pressure, contact electrification occurs between its conductive and dielectric microlayers, creating an electrical charge that transmits information about the state of the material matrix. In addition, it naturally inherits the excellent mechanical adjustability of standard metamaterials. The energy generated by its integrated triboelectric nanogenerator mechanism eliminates the need for a separate power supply, and a small chip records data on the pressure in the cage, which is an important indicator of healing. Data can be read noninvasively using a portable ultrasound scanner.
The proposed cage is not only unique in its detection capabilities, but is also made of a highly adjustable material that can be customized according to the needs of the patient.
“Spinal fusion cages are being widely used in spinal fusion surgeries, but they are usually made of titanium or PEEK polymer materials (a semi-crystalline, high-performance engineering thermoplastic) with certain mechanical properties,” Alavi explained. “The stiffness of our metamaterial intersomatic cages can be easily adjusted. The implant can be 3D printed based on the patient’s specific anatomy before surgery, making it a much more natural fit.”
The team has successfully tested the device on human corpses and is looking to move to animal models. Because the material itself is incredibly adjustable and scalable, the smart sensor design could be adapted to many other medical applications in the future, such as cardiovascular stents or components for knee or hip replacements.
“This is a first-of-its-kind implant that leverages advances in nanogenerators and metamaterials to incorporate multifunctionality into the tissue of medical implants,” Alavi said. “This technological advancement will play an important role in the future of implantable devices.”
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Materials provided by the University of Pittsburgh. Original written by Maggie Lindenberg. Note: Content can be edited by style and length.