High Energy Density, Long Life, Betavoltaic Power Cells for Pacemakers and other Implantable Devices

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Pacemakers are small devices that help control abnormal heart rhythms, called arrhythmia, which can lead to serious, life-threatening conditions, including organ damage, cardiac arrest, and death. Indeed, pacemakers are a highly important treatment option for cardiac arrhythmia with 1,002,664 implanted in 2009, including 225,567 in the U.S, growing at an annual rate of 55.6%. Given the aging population and increased likelihood of arrhythmia as a person ages, the number of implants is expected to increase in the future. There are two main limitations associated with the majority of currently marketed pacemakers, both of which are tied to the battery: usable lifetime and device volume. Typical pacemakers need to be replaced every 5 to 7 years due to the specified lifetime of their electro-chemical batteries, meaning 20% of pacemaker implantations are replacement devices and 76% of those replacements are battery related. This constraint results in significant cost, up to $80,000/per implant in the U.S., as well as health risks and inconvenience for the patient. Pacemaker volume is also an important issue for patients and physicians. Current batteries constitute over 50% of the volume of a conventional model. While pacemaker size has reduced over time, the current footprint remains visible under the skin, and hence, less than ideal from a quality of life perspective. The goal of this research project is to develop a next generation battery for pacemakers and other medical implants through the development of novel textured silicon carbide (SiC) betavoltaics that will provide a more compact and long-lived power source for next-generation implants. Betavoltaics are micro power sources that produce continuous voltage and current by harvesting betas, electrons produced from isotope decay, and converting their energy to electrical power with a semiconductor device. Widetronix's innovation is embedding an isotope layer around the textured features of a wide bandgap semiconductor. Because of the extremely high energy density of the isotope fuel, this technology has the potential to achieve power densities ten-fold greater than existing pacemaker batteries with projected operational lifetimes exceeding 15 years. These features will result in definite improvements to the quality of patient care and, in the long term, reduce the cost of the implantable device over its useful lifetime. Over the course of the NIH Phase I SBIR, Widetronix was able to develop a process for securing an isotope layer (metal tritide) on the surface of our textured SiC device, thereby achieving a consistent beta flux over the active area. The process led to a 3x improvement in the energy density of our betavoltaics. The development under the Phase II will focus on pushing the texturing of the SiC device toward its material limit, etching deeper into the SiC while narrowing the features, thereby allowing the betavoltaic to take full advantage of the extra surface area gained through the texturing process. The goal is to increase the active area density by 6x (from 2.43 cm2/cm2 to 14.58 cm2/cm2), resulting in an energy density that surpasses existing pacemaker batteries (5.8 kJ/cc) and moves us closer to our medical implant partners desired goal. The Phase II aims will involve the investigation and development of process conditions that maximize the exposed betavoltaic surface area while minimizing the device footprint; effectively increasing the devices textured area and thereby maximizing energy density