Fundamental understanding of advanced-material performance under dynamic conditions has remained challenging due to cost- and time-intensive characterization. In many scenarios, prediction of these dynamic responses remains limited to modeling approaches, while comprehensive experimental validation sweeps are unattainable. Microscale dynamic characterization routes such as micro-Kolsky bar and laser-induced impact tests (LIPIT) provide potential solutions for expedited characterization, but their implementation remains challenging. In particular, LIPIT approaches provide limited mechanical information and are single-shot experiments, yielding a single data point per sample.
Focusing on linear dynamic properties of materials, and using mechanical metamaterials as a test bed, we present a characterization scheme for materials that enables capturing the effective dynamic elastic constants as well as their linear dynamic response in a robust and iterative manner. We fabricate architected materials using two-photon lithography with feature sizes on the order of ~1 µm and unit cells on the order of 10 µm, resulting in samples approximately 100 µm tall. To characterize their effective elastic properties, we induce photoacoustic stimuli in a pump-probe scheme to dynamically excite elastic waves in the architected materials and thereby determine the dominant modal response using a common-path interferometric setup. We experimentally reconstruct partial dispersion relations and attenuation properties of the 3D micro-architected materials, present their fully experimental dynamic elastic surfaces, and demonstrate the potential to use dynamic responses to identify defects in these materials. We validate this technique using a variety of 3D architectures along various crystallographic orientations. This exploration merges expertise from ultrafast optics and metamaterial mechanics, elucidating a potential path for iterative and robust characterization of microscale materials
