Shielding Effectiveness of Ferrofluid Layer in the Presence of Oscillating Magnetic Field

This study investigates the effect of an oil-based ferrofluid layer subjected to oscillating magnetic fields on the shielding effectiveness (SE) of the electromagnetic wave (EMW) within 12.4–18 GHz. By leveraging the dynamic crest formations induced by varying the frequency from 0 to 105 Hz, the ferrofluid demonstrated significant adaptability and potential for effective electromagnetic interference (EMI) shielding. Results indicated that the ferrofluid crests exhibited pulsating behavior at lower oscillating frequencies of 1 Hz, enhancing SE to nearly 40 dB at 15.2 GHz. As the oscillation increased to 5 Hz, the crests displayed oscillatory instability, maintaining an SE peak of 37.7 dB at 17.6 GHz. For higher frequencies beyond 15 Hz, crest formation demonstrates a gradual diminishing behavior, transitioning into static or flat states, leading to a reduced SE. Additionally, the results revealed that thicker layers attenuate EM waves more effectively, even as crest dynamics become less pronounced. These findings highlight the capability of ferrofluid layers to achieve high EMI shielding through dynamic surface patterning, with thicker layers contributing to robust, adaptive, and flexible shielding solutions suitable for high-frequency electromagnetic environments.