Constructing Conductive Gratings in Polyurethane Foams for Tunable Electromagnetic Shielding via a Region-selective Silver Plating Process

Abstract

In this study, unique conductive gratings were constructed in polyurethane (PU) foams to achieve tunable electromagnetic shielding. First, a mold enabling region-selective silver plating was fabricated through model design and 3D printing technology. Second, PU foam was placed inside the mold to create controllable exposure regions. Third, a region-selective silver plating process was achieved by exploiting this localized exposure, thereby successfully constructing conductive grating composite foams (grating-Ag/PDA@PU). The effects of the grating number, arrangement pattern, spacing, and incident angle of electromagnetic waves on the electromagnetic interference shielding effectiveness (EMI SE) were systematically investigated, revealing the structure-property relationship between shielding performance and grating geometric parameters. The results indicate that the EMI SE values of a single-layer conductive grating are positively correlated with the number of gratings. For a multilayer conductive grating, staggered parallel arrangements exhibit superior shielding performance compared to simple parallel arrangements. Appropriately increasing the spacing between gratings helps reduce mutual electromagnetic coupling, thereby enhancing the overall EMI SE values. It was also found that a nondestructive electromagnetic shielding switch could be realized simply by flipping the sample. Specifically, the EMI SE values changing from 3.53 dB to 34.04 dB can be achieved by simply flipping the foams. This study provides new insights into the design and fabrication of tunable conductive gratings for use in electromagnetic shielding switches.