Energy-Autonomous Wireless Implantable Sensors Powered by Piezoelectric Transducers with Magnetic Plucking

Wireless sensors have been increasingly used in various industrial applications especially with the proliferation of the Internet of Things. In this work, an energy-autonomous solution for wireless implantable sensors is developed and illustrated, allowing medical implants to be self-sustained within the human body over long terms. This solution consists of a piezoelectric transducer with a tip magnet mounted on an implantable sensor and a wearable rotating magnetic array which can be driven either by human motion or motors. A complete theoretical model has been established in this work to study the electromechanical dynamics and the wireless power transfer capability. Different magnetic array configurations are explored to increase the power transfer distance and output level. A prototype was fabricated and tested in laboratory conditions along with a power management and control solution to verify the concept and the design. The wireless power transfer solution delivers around 0.28 mW power using a 26.5x1.5x0.3 mm piezoelectric beam, over a large transmission distance 18 mm, demonstrating its capability in implementing energy-autonomous wireless implantable sensors

Energy harvesting and wireless transfer in sensor network applications: Concepts and experiences

Advances in micro-electronics and miniaturized mechanical systems are redefining the scope and extent of the energy constraints found in battery-operated wireless sensor networks (WSNs). On one hand, ambient energy harvesting may prolong the systems lifetime or possibly enable perpetual operation. On the other hand, wireless energy transfer allows systems to decouple the energy sources from the sensing locations, enabling deployments previously unfeasible. As a result of applying these technologies to WSNs, the assumption of a finite energy budget is replaced with that of potentially infinite, yet intermittent, energy supply, profoundly impacting the design, implementation, and operation of WSNs. This article discusses these aspects by surveying paradigmatic examples of existing solutions in both fields and by reporting on real-world experiences found in the literature. The discussion is instrumental in providing a foundation for selecting the most appropriate energy harvesting or wireless transfer technology based on the application at hand. We conclude by outlining research directions originating from the fundamental change of perspective that energy harvesting and wireless transfer bring about