A preliminary Life Cycle Assessment of electromagnetic energy harvesting devices. A focus on Magnetic Tunnel Junctions

The Internet of Things (IoT) encompasses a vast network of diverse interconnected smart devices, and their number is expected to rise rapidly. In this context, a critical challenge to face is finding solutions for the supply of adequate quantity of electricity necessary to power these devices. In particular, this means the development of miniature energy-efficient power supplies to ensure sustained autonomous operation. Charging these devices with energy from the environment could offer a valid alternative to reduce environmental concerns. Electromagnetic waves in the microwave spectrum, typically used for wireless data transmission, offer a valuable yet underutilised resource. Emerging electromagnetic energy harvesting technologies, like spin torque devices, show promise in converting unused electromagnetic energy into electricity for IoT devices. However, their reliance on materials categorised as critical and rare could pose potential environmental challenges. This paper aims to preliminarily assess the environmental impacts of Magnetic Tunnel Junctions (MTJs), which are pivotal components in spintronic devices. Through a systematic literature review, key materials used in MTJs are identified, facilitating hotspot mapping. Then, the Life Cycle Assessment (LCA) method is used to evaluate the potential environmental impacts associated with different sizes and efficiency parameters. The results are useful for identifying critical materials within devices and suggesting solutions for reduction or substitution without compromising energy efficiency. This preliminary analysis also aims to guide LCA application to electromagnetic energy harvesters, identifying gaps, limitations, and methodological considerations. Funded by the EU Next Generation initiative through the MUR-PNRR project, this research contributes to the "Innovation Ecosystem - Sicilian MicronanoTech Research and Innovation Center" (SAMOTHRACE - ECS00000022) project.