Paper Number
TM22 My Program
Session
Techniques and Methods
Title
Characterising rough and adhesive single-particle contacts
Presentation Date and Time
October 17, 2024 (Thursday) 10:35
Track / Room
Track 6 / Room 501
Authors
- Scherrer, Simon W. (ETH Zürich, Department of Materials)
- Isa, Lucio (ETH Zürich, Department of Materials)
- Ramakrishna, Shivaprakash N. (ETH Zürich, Department of Materials)
Author and Affiliation Lines
Simon W. Scherrer, Lucio Isa and Shivaprakash N. Ramakrishna
Department of Materials, ETH Zürich, Zürich, Zürich 8093, Switzerland
Speaker / Presenter
Scherrer, Simon W.
Keywords
experimental methods; additve manufacturing; advanced manufacturing; colloids; dense systems; future of rheology; methods; non-Newtonian fluids; particles; polymers; techniques
Text of Abstract
The rheological response of particulate suspensions plays a crucial role in both natural and industrial settings. In particular, suspensions in which the viscosity increases non-linearly above a critical shear stress (shear thickening suspensions) have been studied extensively. The microscopic origin of this phenomenon can be traced back to the emergence of constraints in the relative motion between the particles, which can be induced by turning on frictional and adhesive interactions at contact. In particular, characterising contacts during rolling motion remains extremely challenging, since it is not possible with commonly employed colloidal-probe atomic force microscopy. To address this issue, we present a new approach: a free particle in a liquid is captured by a custom nano-fabricated holder attached to a conventional AFM cantilever and translated horizontally. The studied particles are optically anisotropic to quantitatively track particle rotation, while simultaneously measuring the normal and lateral forces. Using surface-modified silica particles, we demonstrate that an increase in adhesion at the contact or an increase in the roughness at the contact induces the particles to transition from sliding to rolling motion. Notably, the rolling mechanisms qualitatively differ between rough and adhesive substrates, due to the different origin of traction at the contact. In general, the friction experienced by a rolling particle is significantly lower than the one measured during sliding, while the average contact duration increases. With this technique, we now can study contacts akin to those formed in dense particulate suspensions under shear, paving the way for the design of custom surfaces to control rheology, for shear-thickening materials and beyond.