Time-Dependent Assessment of Fibril Assembly and Order by Light Polarization

Microfibrillar structures are fundamental to the dynamics of both biological and physical systems, most relevant to materials based on polysaccharides (cellulose, chitin) and proteins (collagen), including filaments, textiles, sensors and actuators, as well as data/electric/magnetic channels. Among the various properties, alignment (order) is an important factor defining structural, mechanical and functional features. Currently, measurements of fibril order in the nano and microscales rely on scattering and 2D imaging data that is fed to mathematical models, which compromise precision and generality across diverse fibril organizations and applications. For example, studies on fibril order in cellulose biofilms produced by microorganisms is challenged by the random distribution of features in space, including length, diameter, density, orientation, and morphologic or topologic dynamics, which are not considered in conventional approaches. The level of complexity is further increased considering the dynamics of the system, e.g., spatial-temporal factors. To address these challenges and better understand the impact of fibril order on the assembly in living systems, we propose a non-invasive technique utilizing three-dimensional imaging and light polarization analyses. This approach allows us to precisely assess the structural order using a matrix representation and correlating it with responses under different conditions (e.g. mechanical strains). We have synthesized fibers featuring various materials, alignment angles, structures, and organizations—including aligned, semi-aligned, random alignments, and helical configurations. By using a custom-made polarization matrix detection platform, we quantified order in the time domain. The polarization detection enables real-time observation and detailed quantification of the changes in fiber order under mechanical strain. This work provides fundamental support relevant to current efforts related to living matter, self-assembly, energy and health-materials.