Combined AFM−Confocal Microscopy of Oil Droplets: Absolute Separations and Forces in Nanofilms

Tabor, Richard Francis; Lockie, Hannah; Mair, Douglas; Manica, Rogério; Chan, Derek Y. C.; Grieser, Franz; Dagastine, Raymond R.

doi:10.1021/jz2003606

Cited by 41 publications

(42 citation statements)

References 28 publications

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“…[17] On the contrary, some repulsive surface forces, such as van der Waals forces, have been shown to further prevent the surfaces from collapsing or coalescing in order to maintain a minimum fluid thickness between them. [21] In a number of related studies, Chan and coworkers have developed a full numerical theory based on this analysis to describe the dynamic interactions of drops and bubbles measured using AFM (Fig. 3b).…”

Section: Experimental Validationmentioning

confidence: 99%

“…[9,10] These deformations, in turn, can have a profound effect on the hydrodynamic interactions [11], such as those encountered during dynamic force measurements with the atomic force microscope (AFM) [12,13] or the surface forces apparatus (SFA) (see Figure 1b). [14,15] The SFA and AFM are well-suited to study the coupling between soft matter and hydrodynamic interactions, as demonstrated with droplets or bubbles [16][17][18][19][20][21] (Figure 1c(iii)). More recently, these tools have been employed and adapted to study elastohydrodynamic deformation of compliant solids.…”

Section: Introductionmentioning

confidence: 99%

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Elastic deformation during dynamic force measurements in viscous fluids

Wang

Pilkington

Dhong

et al. 2017

Current Opinion in Colloid & Interface Science

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Understanding and harnessing the coupling between lubrication pressure and elasticity provides materials design strategies for applications such as adhesives, coatings, microsensors, and biomaterials. Elastic deformation of compliant solids caused by viscous forces can also occur during dynamic force measurements in instruments such as the surface forces apparatus (SFA) or the atomic force microscope (AFM). We briefly review hydrodynamic interactions in the presence of soft, deformable interfaces in the lubrication limit. More specifically, we consider the scenario of two surfaces approaching each other in a viscous fluid where one or both surfaces is deformable, which is also relevant to many force measurement systems. In this article the basic theoretical background of the elastohydrodynamic problem is detailed, followed by a discussion of experimental validation and considerations, especially for the role of elastic deformation on surface forces measurements. Finally, current challenges to our understanding of soft hydrodynamic interactions, such as the consideration of substrate layering, poroelasticity, viscoelasticity, surface heterogeneity, as well as their implications are discussed.

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Section: Experimental Validationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Elastic deformation during dynamic force measurements in viscous fluids

Wang

Pilkington

Dhong

et al. 2017

Current Opinion in Colloid & Interface Science

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“…The deformation of the drops depends on their size, hydrodynamic interactions, colloidal forces, and surface forces [57,62]. According to recent emulsion stability simulations (ESS) an approximate threshold for drop deformation occurs around 2.5 µm [56,57,63,64].…”

Section: Flocculation Of Oil Dropsmentioning

confidence: 99%

Nanoemulsion stability: Experimental evaluation of the flocculation rate from turbidity measurements

Rahn-Chique¹,

Puertas²,

Romero-Cano³

et al. 2012

Advances in Colloid and Interface Science

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The coalescence of liquid drops induces a higher level of complexity compared to the classical studies about the aggregation of solid spheres. Yet, it is commonly believed that most findings on solid dispersions are directly applicable to liquid mixtures. Here, the state of the art in the evaluation of the flocculation rate of these two systems is reviewed. Special emphasis is made on the differences between suspensions and emulsions. In the case of suspensions, the stability ratio is commonly evaluated from the initial slope of the absorbance as a function of time under diffusive and reactive conditions. Puertas and de las Nieves (1997) developed a theoretical approach that allows the determination of the flocculation rate from the variation of the turbidity of a sample as a function of time. Here, suitable modifications of the experimental procedure and the referred theoretical approach are implemented in order to calculate the values of the stability ratio and the flocculation rate corresponding to a dodecane-in-water nanoemulsion stabilized with sodium dodecyl sulfate. Four analytical expressions of the turbidity are tested, basically differing in the optical cross section of the aggregates formed. The first two models consider the processes of: a) aggregation (as described by Smoluchowski) and b) the instantaneous coalescence upon flocculation. The other two models account for the simultaneous occurrence of flocculation and coalescence. The latter reproduce the temporal variation of the turbidity in all cases studied (380 ≤ [NaCl] ≤ 600 mM), providing a method of appraisal of the flocculation rate in nanoemulsions.

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“…29,35 Droplet deformation can be well predicted for viscous interfaces where droplet shape is described by the Young-Laplace equation. 29,32,[35][36][37][38][39][40] However, there is limited research which considers industrially relevant systems, such as water droplets in oil, 42 or interfaces with significant elasticity, for which the criterion of a Laplacian response no longer holds. 43 Our previous study 44 explored viscoelastic effects encountered in water-in-crude oil emulsion systems.…”

Section: Introductionmentioning

confidence: 99%

Probing Mechanical Properties of Water–Crude Oil Interfaces and Colloidal Interactions of Petroleum Emulsions Using Atomic Force Microscopy

et al. 2017

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Atomic force microscopy (AFM) is frequently used to elucidate complex interactions in emulsion systems. However, comparing results obtained with "model" planar surfaces to curved emulsion interfaces often proves unreliable, since droplet curvature can affect adsorption and arrangement of surface-active species, while droplet deformation affects the net interaction force.In the current study, AFM was utilized to study the interactions between a colloidal probe and water droplet. Force magnitude and water droplet deformation were measured in asphaltene and bitumen solutions of different concentrations at various droplet aging times. Interfacial stiffening and an increase in particle-droplet adhesion force were observed upon droplet aging in bitumen solution. As reported in our previous study (Kuznicki, N. P.; Harbottle, D.; Masliyah, J.; Xu, Z. Dynamic Interactions between a Silica Sphere and Deformable Interfaces in Organic SolventsStudied by Atomic Force Microscopy. Langmuir 2016, 32 (38), 9797−9806), a viscoelasticity parameter should be included in the high force Stokes-Reynolds-Young-Laplace (SRYL) equations to account for the interfacial stiffening and non-Laplacian response of the water droplet at longer aging times. However, following the addition of a biodegradable demulsifier, ethyl cellulose (EC), an immediate reduction in both the particle-droplet adhesion force and the rigidity of the water droplet occurred. Following EC addition, the interface reverted back to a 2 Laplacian response and droplet deformation was once again accurately predicted by the classical SRYL model. These changes in both droplet deformation and particle-droplet adhesion, tracked by AFM, imply a rapid asphaltene/bitumen film displacement by EC molecules. The colloidal probe technique provides a convenient way to quantify forces at deformable oil/water interfaces and characterize the in-situ effectiveness of competing surface active species.

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Combined AFM−Confocal Microscopy of Oil Droplets: Absolute Separations and Forces in Nanofilms

Cited by 41 publications

References 28 publications

Elastic deformation during dynamic force measurements in viscous fluids

Elastic deformation during dynamic force measurements in viscous fluids

Nanoemulsion stability: Experimental evaluation of the flocculation rate from turbidity measurements

Probing Mechanical Properties of Water–Crude Oil Interfaces and Colloidal Interactions of Petroleum Emulsions Using Atomic Force Microscopy

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