2026-05-12 アルゴンヌ国立研究所（ANL）
Under stress, particle interactions exhibit different flow behaviors in soft materials. On the left, repulsive particles create a smooth and predictable flow, while on the right, attractive particles form clumps that lead to uneven shear banding, showcasing the complex dynamics of yielding and resolidification. (Image generated by Google Gemini.)
＜関連情報＞
- https://www.anl.gov/article/tiny-forces-big-effects-how-particle-interactions-control-the-flow-of-soft-materials
- https://www.pnas.org/doi/10.1073/pnas.2514216122
荷電コロイド懸濁液の降伏における微視的ダイナミクスとレオロジーの橋渡し Bridging microscopic dynamics and rheology in the yielding of charged colloidal suspensions
Hongrui He Heyi Liang, Miaoqi Chu, +4 , and Wei Chen
Proceedings of the National Academy of Sciences Published:October 17, 2025
DOI:https://doi.org/10.1073/pnas.2514216122
Significance
Understanding how soft materials yield under stress is essential for both natural processes and industrial applications. However, direct experimental insights into nanoscale dynamics during yielding and their connection to macroscopic rheology remain limited. This study combines advanced X-ray scattering techniques and simulations to examine how microscopic interactions govern macroscopic flow in charged colloidal suspensions. We demonstrate that repulsive systems yield homogeneously, while attractive systems exhibit complex phenomena such as shear banding, delayed yielding, and resolidification, driven by particle dynamics at the boundaries between flowing and arrested regions. These results establish a direct link between interparticle forces and mechanical response, providing a predictive framework for tuning rheology in soft materials.
Abstract
The yielding of soft materials is critical to many natural and industrial processes, yet experimental insights into microscopic aspects of yielding are limited. This study combines angle X-ray scattering, X-ray photon correlation spectroscopy, and in situ rheology (Rheo-SAXS-XPCS) with fast lubrication dynamics simulations to examine how interparticle interactions influence yielding in charged colloidal suspensions. By tuning attraction through salt addition, we compare repulsive and attractive systems under deformation. Repulsive suspensions yield uniformly with Andrade-like creep and minimal structural change. In contrast, attractive suspensions show complex behaviors, including shear banding, delayed yielding, and resolidification, governed by transient dynamics at shear band interfaces. These results directly link microscopic particle dynamics to macroscopic flow and demonstrate how interaction potentials control rheological behavior. This work offers a framework for designing soft materials with tailored properties for applications in coatings, food processing, drug delivery, and other technologies requiring precise mechanical control.
