Sustainable Magnetochromic Flexible Composites for Advanced Optical Sensing and Smart Applications

This study presents the development of sustainable, flexible magnetochromic (MC) materials using Fe₃O₄ (FO) and CoFe₂O₄ (CFO) nanoparticles synthesized via environmentally friendly methods, along with NdFeB (ND) swarf from neodymium-iron-boron magnet waste. These nanoparticles are integrated with thermochromic (TC) pigments and poly-(vinyl alcohol) (PVA), forming a transparent, flexible polymer matrix. The use of green synthesis for FO and CFO minimizes hazardous chemicals and energy consumption, while the recycling of ND swarf addresses waste management and provides a cost-effective magnetic material. The resulting MC materials can be printed using eco-friendly techniques, offering a sustainable alternative to traditional sensing materials. The devices demonstrate fast color changes between red and gray within 3-5 s under an alternating magnetic field (200 Oe, 100 kHz), making them ideal for applications in flexible electronics, smart textiles, and sensors. With a focus on environmental responsibility, these materials meet the increasing demand for sustainable technologies in advanced optical sensing systems.