Spinal fusion surgeries have a high failure rate for difficult-to-fuse patients. A piezoelectric spinal fusion implant was developed to overcome the issues with other adjunct therapies. Stacked generators were used to improve power generation at low electrical load resistances. The effects of the number of layers on average maximum power and the optimal electrical load resistance were characterized. The effects of mechanical preload, load frequency, and amplitude on maximum power and optimal electrical load resistance were also characterized. Increasing the number of layers from one to nine was found to lower the optimal electrical load resistance from 1.00 GΩ to 16.78 MΩ while maintaining maximum power generation. Mechanical preload did not have a significant effect on power output or optimal electrical load resistance. Increases in mechanical loading frequency increased average maximum power, while decreasing the optimal electrical load resistance. Increases in mechanical loading amplitude increased average maximum power output without affecting the optimal electrical load resistance.

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.

Understanding natural head posture in animals is improtant in interpreting their biomechanics and behavior. For extinct animals, natural posture cannot be directly determined from the fossil record. There have been few prior studies of animal line of sight and head posture. Most line of sight studies have focused on the breadth of binocular vision versus panoramic vision in relation to behavior (predator type or grazer, for instance) or the animals typical environment (open or cluttered) [1]. For head posture some have studied changes in cognition or the environment or related aspects like the eyeball orientation as head posture changes [2]. Still others have focused on the areas of the brain that control 3D head position [3]. However, none of these studies address a method to determine the natural head posture or angle. While there currently is no definitive way to determine natural head angle in extinct animals, it seems reasonable to assume that the natural head posture would place the line of sight in the horizontal plane for most species. Therefore, we hypothesized that the opening for the optical (the optical foremen) and the eye socket structure itself can be used to accurately determine the natural head posture for a large portion of extant and extinct animal species. Specifically, if the skull is oriented such that the plane of sight (the plane common to both lines of sight) is horizontal, then the skull will be in the natural posture. If this hypothesis is shown to be valid, it will provide naturalists a reliable tool to determine the natural head posture (head angle) of extinct animals. The objective of this study was to test the above hypothesis on animals in the Felidae (cats).