Observing Deformation‐Induced Backscattering in Flexible Valley‐Hall Topological Metasurfaces

Abstract Topological metasurfaces based on the quantum valley Hall effect have garnered attention for their ability to enable novel physical phenomena. However, the propagation characteristics of flexible topological metasurfaces under bending and folding remain underexplored, leaving open questions about the behaviors of topological edge states in these configurations. This study investigates edge‐state propagation and frequency response in topological insulator metasurfaces under varying degrees of circular bending and dihedral folding. A flexible topological insulator is designed, fabricated, and tested with a passband between 4.4 and −4.6 GHz, monitoring how its transmission passband changes as the curvature radius decreases from 400 to 100 mm. Simulations and experimental measurements reveal how the transmission frequency response and near‐field distribution evolve as the metasurface undergoes folding from 90° to 30°. Results show that both the topological passband and transmission gradually vary with reduced folding angles, while arc‐shaped bending minimally affects the propagation path, though the passband narrows slightly with increased curvature. To illustrate the impact, metasurface communication performance between planar and folded configurations (90° to 30°) is compared, observing a notable performance drop after folding. This study aims to enhance the understanding of edge‐state properties in topological systems under deformation and promote further advancements in flexible topological devices.