Non-contact Probing of Effective Elastic Constants in 3D Micro-Architected Materials

We present a non-contact characterization scheme for micro-architected materials that enables capturing the effective elastic constants as well as their linear dynamic response in a robust and iterative manner. In this work, micro-architected materials are fabricated using a two-photon lithography technique enabling feature sizes on the order of ~1 µm. To characterize their effective elastic constants, we induce photoacoustic stimuli in a pump-probe scheme to excite elastic waves in the architected materials and determine the modal response using a common-path interferometric setup. Through systematic tuning of the wave vector, we reconstruct the dispersion relations of the materials. We validate this technique using a variety of 3D architectures, and we compare our non-contact properties to those measured via classical nanoindentation techniques and computational homogenization models. This exploration merges expertise from ultrafast optics and metamaterial fabrication, elucidating a potential path for iterative and robust characterization of metamaterials in a dynamic regime. The findings could enable research opportunities for microscale metamaterials as phononic devices, or even provide a novel versatile approach to expedite mechanical-property explorations of the same.