Magnetochromic Elastomer With Instant Color Changes: A Study of the Influence of Material Composition

Magnetochromic materials change color upon variation in an external magnetic field. A magnetochromic elastomer resulting from the dispersion of magnetic nanoparticles (MNPs) in a liquid and subsequent emulsification in a crosslinkable polydimethylsiloxane (PDMS) is presented. The MNPs form rod‐like structures under an external magnetic field, aligning with the field and allowing light to pass through the elastomer. The elastomer thus changes from dark grey to transparent/light grey. Polyethylene glycol 200 (PEG200) is selected as carrier liquid due to the faster movement of MNPs herein than in glycerol, leading to more rapid color changes in the films. The influence of magnetic particle types (commercial, superparamagnetic, and surfactant‐coated) on the magnetochromic effects is investigated. All films exhibit optical density changes upon exposure to a magnetic field. Moreover, the films retain their color‐changing ability after cycles of 40 times exposure to a magnetic field. Compared to the synthesized superparamagnetic particles, the films with commercial particles display superior optical density change abilities, suggesting commercial MNPs are more suitable for magnetochromic films. The obtained films have promising applications as magnetical field sensors due to their simple storage requirements, rapid response, and excellent repeatability. Magnetochromic films are effectively fabricated through the incorporation of Fe3O4 nanoparticles (non‐superparamagnetic particles) into droplets of two‐phased PEG200‐PDMS elastomers. The resulting films achieve rapid, reversible, and repeatable changes in optical properties, transitioning from black/dark grey to light grey/transparent upon the application of the magnetic field, offering potential applications as magnetic field sensors.