Schroyen Bram, Hsu Chiao-Peng, Isa Lucio, Van Puyvelde Peter, Vermant Jan
Department of Materials, ETH Zürich, 8032 Zürich, Switzerland.
Department of Chemical Engineering, KU Leuven, 3001 Heverlee, Belgium.
Phys Rev Lett. 2019 May 31;122(21):218001. doi: 10.1103/PhysRevLett.122.218001.
The collective properties of colloidal suspensions, including their rheology, reflect an interplay between colloidal and hydrodynamic forces. The surface characteristics of the particles play a crucial role, in particular, for applications in which interparticle distances become small, i.e., at high concentrations or in aggregates. In this Letter, we directly investigate this interplay via the linear viscoelastic response of the suspensions in the high-frequency regime, using particles with controlled surface topographies, ranging from smooth to hairy and rough particles. We focus directly on the stresses at the particle level and reveal a strong impact of the surface topography on the short-range interactions, both dissipative and elastic. As the particle topography becomes more complex, the local stresses depend on how the topography is generated. The findings in this Letter, in particular, show how changes in topography can both screen or enhance the dissipation, which can be used to engineer the properties of dense or aggregated suspensions.
胶体悬浮液的集体性质，包括其流变学，反映了胶体力和流体动力学力之间的相互作用。颗粒的表面特性起着至关重要的作用，特别是在颗粒间距离变小的应用中，即在高浓度或聚集体中。在本信函中，我们通过使用具有可控表面形貌的颗粒，从光滑颗粒到有毛颗粒和粗糙颗粒，在高频区域直接研究悬浮液的线性粘弹性响应来探究这种相互作用。我们直接关注颗粒层面的应力，并揭示表面形貌对短程相互作用（包括耗散和弹性）的强烈影响。随着颗粒形貌变得更加复杂，局部应力取决于形貌是如何产生的。本信函中的研究结果尤其表明，形貌的变化如何既能屏蔽或增强耗散，这可用于设计致密或聚集悬浮液的性质。
