Stacked macro fiber piezoelectric composite generator for a spinal fusion implant

Abstract

A manufacturing method was developed to create a piezoelectric 3-layer stacked, macro fiber composite generator operating in d 33 mode to promote bone growth in spinal fusion surgeries. A specimen of 9 × 17 × 9 mm thick was constructed from 800 μm diameter PZT fibers and medical grade epoxy. Electromechanical testing was performed at three stages of manufacturing to determine the influence of these processes on power generation. An average peak power of over 335 μW was generated in the heat-treated specimen during simulated human body loads. The work provides insights into manufacturing methods for lowered source impedance power generation for a variety of applications.

Stacked PZT Discs Generate Necessary Power for Bone Healing through Electrical Stimulation in a Composite Spinal Fusion Implant

“…In contrast to previous studies, investigating piezoelectric composite spinal fusion implants that used a nine-layer stack of 48 PZT macro fibers, the current study investigated the impact on power output when switching to a stack of PZT discs [25]. To validate this switch, the average power output from the 15-disc implants was compared to previous studies that assessed power production from a composite TLIF throughout the manufacturing process [25,26]. The total volume of PZT in the macro fiber implants was 217 mm 3 .…”

“…This was very similar to the 230 mm 3 volume of PZT in the 15-disc implants. Across the resistance sweep, the 15-disc implant outperformed both the pre-encapsulated and post-encapsulated TLIF implants (Figure 4) [25,26]. The ratio of PZT cross-sectional area to footprint surface area, for the pre-encapsulation and post-encapsulated macro-fiber implant, was 30% and 16%, respectively, as compared to 27% for the disc implants.…”

“…Previous work has evaluated the use of PZT composites to power in vivo devices, such as embedded MEMS devices and wearable sensors [28,29,40]. Using the generated current of such devices to produce electrical stimulation to increase bone healing in lumbar spinal fusion has only recently been studied [25,26,27,41]. These studies utilized PZT macro fibers embedded in an epoxy matrix to improve the mechanical properties of the brittle ceramic.…”

“…As seen in Figure 4, the 15-disc implant was able to produce substantially more power across the resistance sweep as compared to the pre- and post-encapsulated PZT macro-fiber implants, for similar PZT volumes, despite a 5% decrease in PZT surface area to implant footprint [25,26]. This increase in power could be attributed to either the PZT discs themselves or the fabrication method used to produce the PZT disc composite implants.…”

“…Previous studies have investigated using a piezoelectric macro-fiber composite, as the material for spinal interbody implants, to supply the necessary power to deliver electrical stimulation to the site of lumbar fusion [25,26,27]. These composites allowed the piezoelectric (PZT) macro fibers to strain in response to typical lumbar spinal loads and produce an electrical charge, and the matrix material added the needed toughness that the brittle PZT lacks.…”