Intrinsic modal dispersion confines most elastic metasurfaces to a single encoded functionality, and mode-resolved analysis of plate-guided waves therefore still relies on bulky transducers or extensive signal postprocessing. Here, we introduce a passive elastic mode-resolver for Lamb-wave identification based on a frequency-specific dispersion-engineered metasurface. A birefringent meta-atom is designed to exhibit pronounced mode-dependent dispersion, and its dynamic behavior is systematically characterized through eigenanalysis. By leveraging the fabrication flexibility of elastic metasurfaces, the required meta-atoms can be arranged without relying on extensive meta-atom libraries or computationally intensive optimization. Designed to operate at a specific frequency of 100 kHz, the proposed metasurface selectively focuses incident S0 and A0 modes to spatially encoded positions, thereby enabling identification of the propagating mode from the resulting intensity distribution. By integrating a piezoelectric element at each encoded focal position, the mechanically concentrated wave energy is converted into a mode-dependent electrical signal, enabling passive electrical readout of the encoded modal response. As a result, the mode-resolver provides a compact and passive alternative to bulkier systems conventionally used in structural health monitoring, ultrasonic sensing, and related industrial applications. By independently processing mode-dependent information within a single passive platform, it offers a practical route toward expanded mechanical functionality in transportation infrastructure, large civil structures, and smart facilities.
Lee et al. (Fri,) studied this question.