1] CNR-ISC, UOS Sapienza, P.le A. Moro 2, Roma I-00185, Italy [2] Dipartimento di Fisica, 'Sapienza' Università di Roma, P.le A. Moro 2, Roma I-00185, Italy.
Dipartimento di Fisica, 'Sapienza' Università di Roma, P.le A. Moro 2, Roma I-00185, Italy.
Nat Commun. 2014;5:3267. doi: 10.1038/ncomms4267.
Percolation and critical phenomena show common features such as scaling and universality. Colloidal particles, immersed in a solvent close to criticality, experience long-range effective forces named critical Casimir forces. Building on the analogy between critical phenomena and percolation, here we explore the possibility of observing long-range forces near a percolation threshold. To this aim, we numerically evaluate the effective potential between two colloidal particles dispersed in a chemical sol, and we show that it becomes attractive and long-ranged on approaching the sol percolation transition. We develop a theoretical description based on a polydisperse Asakura-Oosawa model that captures the divergence of the interaction range, allowing us to interpret such effect in terms of depletion interactions in a structured solvent. Our results provide the geometric analogue of the critical Casimir force, suggesting a novel way for tuning colloidal interactions by controlling the clustering properties of the solvent.
渗流和临界现象表现出一些共同的特征，如标度和普遍性。胶体粒子，沉浸在接近临界的溶剂中，会经历被称为临界 Casimir 力的长程有效力。基于临界现象和渗流之间的类比，我们在这里探索在渗流阈值附近观察长程力的可能性。为此，我们通过数值评估了在化学溶胶中分散的两个胶体粒子之间的有效势，结果表明，当接近溶胶渗流转变时，它会变得具有吸引力和长程性。我们基于多分散的 Asakura-Oosawa 模型提出了一种理论描述，该模型捕捉到了相互作用范围的发散，使我们能够根据结构化溶剂中的耗尽相互作用来解释这种效应。我们的结果提供了临界 Casimir 力的几何类比，这为通过控制溶剂的聚类性质来调整胶体相互作用提供了一种新方法。
