Light sheet imaging in granular materials: interdisciplinary opportunities

Granular materials, ubiquitous in geophysics, chemical engineering, biophysics and soft matter physics, present unique challenges for optical imaging due to their opaque and heterogeneous nature. This perspective paper provides a comprehensive overview of opportunities in Light Sheet Microscopy (LSM) techniques for imaging granular materials, emphasizing refractive index matching as a critical tool for visualizing internal deformations and flow dynamics. By matching the refractive indices of solid particles and surrounding fluids, researchers can create “transparent soils” or analogous systems, enabling detailed examination of particle interactions, strain fields, and fluid flow. To comprehensively introduce opportunities for future research, the review explores the evolution of LSM, from early broadband light sources to modern laser and LED-based systems, highlighting advancements in wavefront shaping and contrast generation through scattering and fluorescence. The paper also surveys some innovative approaches for LSM and index matching, such as Sephadex spheres and cryolite. Emerging techniques, such as wavefront shaping and three dimensional imaging with event cameras, are presented as promising avenues for future research. Additionally, the review connects granular imaging to biological systems, demonstrating its relevance for studying microbial motility, biofilm growth, and tissue engineering. This perspective paper aims to guide and inspire researchers in selecting and refining LSM techniques for advancing the understanding of complex particulate systems.