Jan Vermant

Last Name

Vermant

First Name

Jan

ORCID

0000-0002-0352-0656

Organisational unit

09482 - Vermant, Jan / Vermant, Jan

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Publications1 - 10 of 153

Rheo-optical Analysis of Functionalized Graphene Suspensions
Reddy, Naveen K.; Natale, Giovanniantonio; Prud'homme, Robert K.; et al. (2018)
Langmuir
No yield stress required: Stress-activated flow in simple yield-stress fluids
Pagani, Gabriele; Hofmann, Martin; Govaert, Leon E.; et al. (2024)
Journal of Rheology
An elastoviscoplastic constitutive equation is proposed to describe both the elastic and rate-dependent plastic deformation behavior of Carbopol® dispersions, commonly used to study yield-stress fluids. The model, a variant of the nonlinear Maxwell model with stress-dependent relaxation time, eliminates the need for a separate Herschel-Bulkley yield stress. The stress dependence of the viscosity was determined experimentally by evaluating the steady-state flow stress at a constant applied shear rate and by measuring the steady-state creep rate at constant applied shear stress. Experimentally, the viscosity’s stress-dependence was confirmed to follow the Ree-Eyring model. Furthermore, it is shown that the Carbopol® dispersions used here obey time-stress superposition, indicating that all relaxation times experience the same stress dependence. This was demonstrated by building a compliance mastercurve using horizontal shifting on a logarithmic time axis of creep curves measured at different stress levels and by constructing mastercurves of the storage- and loss-modulus curves determined independently by orthogonal superposition measurements at different applied constant shear stresses. Overall, the key feature of the proposed constitutive equation is its incorporation of a nonlinear stress-activated change in relaxation time, which enables a smooth transition from elastic to viscous behavior during start-up flow experiments. This approach bypasses the need for a distinct Herschel-Bulkley yield stress as a separate material characteristic. Additionally, the model successfully replicates the observed steady-state flow stress in transient-flow scenarios and the steady-state flow rate in creep experiments, underlining its effectiveness in capturing the material’s dynamic response. Finally, the one-dimensional description is readily extended to a full three-dimensional finite-strain elastoviscoplastic constitutive equation.
Self-assembly of ellipsoidal particles at fluid-fluid interfaces with an empirical pair potential
Luo, Alan M.; Vermant, Jan; Ilg, Patrick; et al. (2019)
Journal of Colloid and Interface Science
Light-switchable propulsion of active particles with reversible interactions
Vutukuri, Hanumantha R.; Lisicki, Maciej; Lauga, Eric; et al. (2020)
Nature Communications
Active systems such as microorganisms and self-propelled particles show a plethora of collective phenomena, including swarming, clustering, and phase separation. Control over the propulsion direction and switchability of the interactions between the individual self-propelled units may open new avenues in designing of materials from within. Here, we present a self-propelled particle system, consisting of half-gold-coated titania (TiO2) particles, in which we can quickly and on-demand reverse the propulsion direction, by exploiting the different photocatalytic activities on both sides. We demonstrate that the reversal in propulsion direction changes the nature of the hydrodynamic interaction from attractive to repulsive and can drive the particle assemblies to undergo both fusion and fission transitions. Moreover, we show these active colloids can act as nucleation sites, and switch rapidly the interactions between active and passive particles, leading to reconfigurable assembly and disassembly. Our experiments are qualitatively described by a minimal hydrodynamic model.
Validation via rheological experiments of theories for the flow through porous media
Minale, Mario; Carotenuto, Claudia; Vananroye, Anja; et al. (2014)
86th Annual Meeting Program and Abstracts
Particles at interfaces
Vermant, Jan (2014)
Divide, Conquer, and Stabilize: Engineering Strong Fluid-Fluid Interfaces
Bayles, Alexandra Victoria; Vermant, Jan (2022)
Langmuir
In multiphase materials, structured fluid-fluid interfaces can provide mechanical resistance against destabilization. Coarsening, coalescence, and significant deformation can be stalled with appropriate interfacial rheology and thus preserve interface integrity. Often, interfacial "strength"is generated by dense, packed surface populations, which are challenging to achieve through gradual, equilibrium-limited adsorption. Recent efforts have focused on developing new methods to produce kinetically trapped interfacial structures that possess desirable viscoelasticity or viscoplasticity, sometimes even with sparse populations. In creating these interfaces, we should recognize that the processing history is deterministic and offers alternative handles to engineer useful rheology. In this Perspective, we consider what can be achieved by designing not only the intrinsic qualities of surface-active species but also the process that brings them to the interface. We contrast different classes of processing history through a somewhat historical lens: after creating an interface ("divide"), what ("conquering") strategies exist for populating it with agents that ensure stabilization? Navigating the delicate interplay among property, structure, and processing history is required to improve material and energy use and to realize unique multiphase materials.
Emulsions Stabilized by Chitosan-Modified Silica Nanoparticles: PH Control of Structure-Property Relations
Alison, Lauriane; Demirörs, Ahmet; Tervoort, Elena; et al. (2018)
Langmuir
In food-grade emulsions, particles with an appropriate surface modification can be used to replace surfactants and potentially enhance the stability of emulsions. During the life cycle of products based on such emulsions, they can be exposed to a broad range of pH conditions and hence it is crucial to understand how pH changes affect stability of emulsions stabilized by particles. Here, we report on a comprehensive study of the stability, microstructure, and macroscopic behavior of pH-controlled oil-in-water emulsions containing silica nanoparticles modified with chitosan, a food-grade polycation. We found that the modified colloidal particles used as stabilizers behave differently depending on the pH, resulting in unique emulsion structures at multiple length scales. Our findings are rationalized in terms of the different emulsion stabilization mechanisms involved, which are determined by the pH-dependent charges and interactions between the colloidal building blocks of the system. At pH 4, the silica particles are partially hydrophobized through chitosan modification, favoring their adsorption at the oil–water interface and the formation of Pickering emulsions. At pH 5.5, the particles become attractive and the emulsion is stabilized by a network of agglomerated particles formed between the droplets. Finally, chitosan aggregates form at pH 9 and these act as the emulsion stabilizers under alkaline conditions. These insights have important implications for the processing and use of particle-stabilized emulsions. On one hand, changes in pH can lead to undesired macroscopic phase separation or coalescence of oil droplets. On the other hand, the pH effect on emulsion behavior can be harnessed in industrial processing, either to tune their flow response by altering the pH between processing stages or to produce pH-responsive emulsions that enhance the functionality of the emulsified end products.
Acoustic trapping of active matter
Takatori, Sho C.; de Dier, Raf; Vermant, Jan; et al. (2016)
Nature Communications
Tension control and lipid microdomain formation using planar large area model biomembranes
Beltramo, P.J.; Vermant, Jan (2016)

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