Determination of Clinical Efficacy of Ultrasound Stimulation on Piezoelectric Composites for Power Generation Applications

Abstract

Each year in the United States there are over one million fractures that occur [1]. When a bone breaks, regardless of the severity, it is referred to as a fracture. Individuals suffering from a fracture typically undergo some form of clinical intervention ranging from a splint to orthopedic surgery to increase the body’s natural ability to fuse the bone. This does not always occur, and some fractures never fuse resulting in a non-union. Bone stimulating adjunct therapies are available, to aid in bone healing, but often require patient compliance or battery packs, but these therapies have restrictions too such as the limited lifespan of batteries. Self-powered generators comprised of piezoelectric composite materials have shown promising results in bone stimulation applications under physiological loading conditions. To increase the effectiveness of these materials in clinical applications the use of ultrasound loading was investigated for use when physiological loading is not possible. Twelve piezoelectric composite specimens (n=6 for both 0.0 mm and 0.8 mm CLACS groups) were manufactured using three stacked, lead zirconate titanate (PZT) discs, wired with the intent to be connected in parallel, encapsulated with medical grade epoxy. The effect of ultrasound intensity (0.1, 0.5, and 1.0 W/cm2 ), compliant layer thickness (0.0 mm and 0.8 mm), and ultrasound application angle (0°, 45°, and 90°) on power generation was investigated for all specimens. An increase in ultrasound intensity resulted in an increase in power production for all specimens. At an application angle of 0° the 0.8 mm CLACS group produced more power than the 0.0 mm group, but a reversed trend was observed at angles of 45° and 90°. Lastly, when compared to 0°, the power output of both specimen groups decreased significantly in the 45° and 90° conditions at all intensities. This study demonstrations that ultrasound is a viable option for stimulating PZT composites intended for power generating applications where physiological loading is not applicable.