A Multifunctional Reconfigurable Frequency-Selective Surface Using Liquid-Metal Alloy

This communication describes a miniaturized reconfigurable frequency-selective surface (FSS) that incorporates a liquid-metal alloy injected into an elastomer. The structure comprises a meandered pattern engraved on a flexible dielectric substrate, where the liquid metal [eutectic gallium indium (EGaIn)] adopts the geometry of the microfluidic channels. The novelty of the proposed design lies in its multifunctional response, switching from all-pass to bandpass/bandstop characteristic, depending on whether EGaIn is injected in the microchannels. The liquid-metal-filled structure, being asymmetric in nature, selectively realizes bandpass operation for a specific polarization, whereas bandstop response is observed under orthogonal polarization. Furthermore, the design exhibits miniaturization performance during bandpass response (at 1.37 GHz), corresponding to unit cell dimensions of 0.059λ ₀ × 0.059λ ₀ . The structure was analyzed through the derivation of equivalent circuit models and several parametric variations. Finally, the proposed multifunctional FSS was fabricated by laser etching, and the filter parameters were experimentally verified under normal as well as oblique incidence.