High-speed, 3D volumetric displacement and strain mapping in soft materials using Light Field Microscopy
Selda Buyukozturk, Alexander Landauer, Jing Zhang, Luke Summey, Angel Chukwu, Christian Franck
Background: High strain-rate deformations of soft materials have several applications which presents an experimental need to measure at-rate 3D volumetric spatial information. While 2D- and 3D-digital image correlation, digital volume correlation, and particle tracking techniques have been able to reconstruct full-field displacements with great resolution, experimentally obtaining volumetric information and applying these techniques at high rates remains a significant challenge, especially at small, micrometer length scales. Methods: To conduct 3D volumetric imaging at high (100 Hz to 10 kHz) or ultra-high rates (10+ kHz) we designed a full-field volumetric light-field microscopy system paired with post-processing and volumetric particle tracking routines to quantify 3D volumetric deformations. Light field microscopy uses the principles of low-angle tomographic volume reconstruction with a microlens array to generate parallax within a single 2D image, which is used for volume reconstruction of a transparent material seeded with fluorescent particles. The algorithm then segments and localizes the particles, and tracks the cumulative motion of the particles throughout a reconstructed image volume. Results: To validate the technique, both synthetic images and gels with embedded particles underwent deformations at high strain-rates.We simulate the light-field representation of particles undergoing motion with ray tracing and investigate the sensitivity and noise floor of the measurement technique. In experiments, a custom-built simple shear device deformed the gel at assorted applied strain rates, while light-field images were collected at between 500 frames per second and 2000 frames per second. Conclusion: By combining light field microscopy with our recently developed topology-based 3D particle tracking algorithms we demonstrate accurate resolution of volumetric displacement fields in soft, transparent materials undergoing high rate deformations.
, Landauer, A.
, Zhang, J.
, Summey, L.
, Chukwu, A.
and Franck, C.
High-speed, 3D volumetric displacement and strain mapping in soft materials using Light Field Microscopy, Experimental Mechanics, [online], https://doi.org/10.1007/s11340-022-00885-z, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=932900
(Accessed December 1, 2023)