Zunke Christoph, Bewerunge Jörg, Platten Florian, Egelhaaf Stefan U, Godec Aljaž
Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
Institute of Biological Information Processing, Biomacromolecular Systems and Processes (IBI-4), Forschungszentrum Jülich, 52425 Jülich, Germany.
Sci Adv. 2022 Jan 21;8(3):eabk0627. doi: 10.1126/sciadv.abk0627.
In nature and technology, particle dynamics frequently occur in complex environments, for example in restricted geometries or crowded media. These dynamics have often been modeled invoking a fractal structure of the medium although the fractal structure was only indirectly inferred through the dynamics. Moreover, systematic studies have not yet been performed. Here, colloidal particles moving in a laser speckle pattern are used as a model system. In this case, the experimental observations can be reliably traced to the fractal structure of the underlying medium with an adjustable fractal dimension. First-passage time statistics reveal that the particles explore the speckle in a self-similar, fractal manner at least over four decades in time and on length scales up to 20 times the particle radius. The requirements for fractal diffusion to be applicable are laid out, and methods to extract the fractal dimension are established.
在自然界和技术领域，粒子动力学经常发生在复杂环境中，例如在受限几何形状或拥挤介质中。尽管分形结构只是通过动力学间接推断出来的，但这些动力学通常通过调用介质的分形结构进行建模。此外，尚未进行系统研究。在这里，在激光散斑图案中移动的胶体粒子被用作模型系统。在这种情况下，实验观测结果可以可靠地追溯到具有可调分形维数的底层介质的分形结构。首次通过时间统计表明，粒子至少在四个数量级的时间内以及在长度尺度达到粒子半径20倍的情况下，以自相似、分形的方式探索散斑。阐述了适用分形扩散的条件，并建立了提取分形维数的方法。
