Macroscopic Viscosity Research Articles

Effects of sodium alginate and locust bean gum on dough rheology and microstructures, and bread quality

AbstractBackground and ObjectivesStrengthening effects of sodium alginate (AG, anionic gum) and locust bean gum (LBG, neutral gum) on dough's network structures were investigated.FindingsAmong all samples, dough containing 0.6% AG showed the longest development and stability time, which was longer than that containing 0.6% LBG by 7.8% and 15.5%, respectively. The relative elastic part of maximum creep compliance (36.26%–59.13%), zero‐shear viscosity (3.69–6.35 × 106 Pa s), elasticity index (0.17–0.44 nm−2), and macroscopic viscosity index (0.14–0.39 nm−2 s) significantly increased with adding AG and LBG. Results of extensograph and dynamic rheology suggested that adding NaCl decreased the tensile energy, storage modulus, and loss modulus of dough containing AG, which might be related to the presence of electrostatic interactions between dough and AG. The bread containing 0.6% AG had a higher specific volume (3.30 ml g−1), height/width ratio (0.74), and springiness (0.93) compared with the bread containing 0.6% LBG.ConclusionsThese results showed denser gluten networks were formed in dough containing AG with electrostatic interactions than in dough containing LBG with hydrogen‐bonding interactions, indicating that electrostatic interactions had a more pronounced effect on dough's network structures than hydrogen‐bonding interactions.Significance and NoveltyThis investigation could provide useful information for the potential application of AG in the development of whole wheat bread.

Interactions between unfolding/disassembling behaviors, proteolytic subfragments and reversible aggregation of oxidized skeletal myosin isoforms at different salt contents

Myosin filament plays a critical role in water-trapping and thermodynamic regulation during processing of brined muscle foods. The redox state and availability of proteolytic/antioxidant enzymes affected by salt may change the ion-binding capacity of myosin consequently contributing to swelling and rehydration. Thus, this study investigated the impact of different salt content (0%, 1%, 2%, 3%, 4%, 5% NaCl) and oxidation in vitro (10 mM H2O2/ascorbate-based hydroxyl radical (OH)-generating system) on the oxidative stability, solubility/dispersion capacity, chymotrypsin digestibility, aggregation site and the microrheological properties of isolated porcine myosin. The result showed that, brining at 2% salt exposed more sulfhydryl groups and inhibited the formation of disulfide bond, whereby smaller dispersed structure (diameter within 10–50 nm) and higher Ca2+-ATPase activity of the denatured myosin were observed. Accordingly, gel electrophoresis showed that myosin S1 and HMM subunits were highly oxidized and susceptible to reversible assembles. Despite enhanced hydrophobic interactions between swelled myosin at 3% salt content, ≥4% salt greatly promoted the exposure/polarization of tryptophan and cross-linking structures, mainly occurring at myosin S2 portion. The results of micro-rheology proved that oxidized myosin formed a tighter heat-set network following rehydration at high ion strength (≥4% salt), suggesting an increased inter-droplet resistance and macroscopic viscosity. This work is expected to give some useful insights into improved texture and functionality of engineered muscle foods.

A homogenization model for the rheology and local field statistics of suspensions of particles in yield stress fluids

We investigate the rheological behavior of athermal particle suspensions using experiments and theory. A generalized version of the homogenization estimates of Ponte Castañeda and Willis [J. Mech. Phys. Solids, 43(12), 1919–1951 (1995)] is presented for the effective viscosity of athermal suspensions accounting for additional microstructural features (e.g., polydispersity) via an empirical parameter, λ. For the case of identically sized spheres dispersed with statistical isotropy in a Newtonian fluid, the parameter λ is estimated from the results of Batchelor and Green [J. Fluid Mech. 56(2), 375–400 (1972)] for the Huggins coefficient. Predictions for the macroscopic viscosity are found to be in good agreement with measurements for monodisperse polymethyl methacrylate (PMMA) spheres in glycerol, as well as for the empirical Krieger–Dougherty equation for the shear viscosity. The proposed estimates have the added benefit that they can also be used to get information on the statistics of the stress and strain-rate fields in the fluid and particle phases. In addition, results for the effective shear viscosity are used in combination with the linear comparison method of Ponte Castañeda [J. Mech. Phys. Solids 39(1), 45–71 (1991)] to generate the corresponding estimates for the effective macroscopic behavior and field statistics of particle suspensions in (viscoplastic) yield stress fluids. Good agreement is also found between the theoretical estimates and experimental results for the effective yield and flow stress of suspensions with monodisperse PMMA spheres in Carbopol. Finally, it is argued that the results for the phase averages and fluctuations of the stress and strain-rate fields can be used to provide a physical interpretation for the parameter λ in terms of the polydispersity of the suspension and its implications for the percolation threshold.

Towards printable water-in-polymer salt electrolytes for high power organic batteries

Internet-of-things which requires electronics, energy convertor and storage must be low-cost, recyclable and environmentally friendly. In the development of printed batteries, ideally all the components (electrode and electrolyte) must be printable to ensure low-cost manufacturing via printing technologies. Most of the printed batteries suffer with low power. One of the reasons is the poor ionic conductivity of the electrolyte due to the high viscosity needed for printing relatively thick layers. In the present work we have demonstrated a new class of electrolyte promising for printed organic batteries following the concept of water-in-polymer salt electrolytes (WIPSEs). These highly concentrated electrolytes of potassium polyacrylate are non-flammable, low cost and environmentally friendly. They possess high ionic conductivities (45–87 mS/cm) independent on the macroscopic viscosities varying from 7 to 33000 cP. The decoupling between ionic transport and macroscopic viscosity enables us to demonstrate organic batteries based on WIPSEs that can deliver a high and constant power (∼4.5 kW/kg; 7.1–11 mW/cm2) independent on the viscosity of the electrolytes. The tunability of the viscosity presents a prerequisite for printed technology manufacturing and compatibility with printed batteries.

Rotational relaxation dynamics study of rhodamine 800 in series of primary alcohols solvents

Rotational reorientation times of rhodamine 800 laser dye have been studied in a series of primary alcohols at room temperature by using steady-state and picosecond time-resolved fluorescence spectroscopy. Experimental rotational reorientation time shows, it increases linearly when the macroscopic viscosity of solvents increases. Hydrodynamic (SED) and Quasi hydrodynamic (GW and DKS) friction models qualitative analysis has been performed to determine mechanical friction contribution to the total friction experienced by laser dye. The results found interestingly that theoretically predicted rotational reorientation times underestimate experimental values.Deviations from the above models enable us to test for dielectric friction (NZ, ZH, and AW) theories and hydrogen bonding possibility between free clo-4 radical and –OH group of alcohol.

Unexpected molecular dynamics of ethanol in hydrogen-bonded binary mixtures, ethanol-octanol and ethanol-water

In view of getting a quantitative picture of the dynamics in mixtures of hydrogen-bonded liquids, in particular the ternary water-ethanol-octanol, we examine in this paper the dynamics of two binary systems: ethanol-water and ethanol-octanol. Our multiscale investigation includes quasi-elastic neutron scattering for the characterization of the dynamics at the molecular scale, completed by NMR at the mesoscopic scale and eventually compared with macroscopic viscosity properties. We highlight the decrease of diffusivity in pure alcohols when increasing the lengthscale and conjecture its relation with the two processes measured in dielectric spectroscopy. While the behaviour of ethanol-water is well understood, unexpected inversion of the slowest component between the micro and the mesoscale are evidenced in the ethanol-octanol mixture. This effect could be at the origin of the negative viscosity excess in the mixture of alcohols.

Comparison of oil-in-water emulsions prepared by ultrasound, high-pressure homogenization and high-speed homogenization

This study was designed to compare the properties of myofibrillar protein (MP) stabilized soybean oil-in-water emulsions fabricated by ultrasound-assisted emulsification (UAE), high-pressure homogenization (HPH) and high-speed homogenization (HSH). The emulsion properties, droplet characteristics, interfacial proteins, protein exposure extent, microrheological properties, multiple light scattering results, and 7 d storage stabilities of the three emulsions were specifically investigated. Our results indicate that UAE and HPH were better emulsification methods than HSH to obtain high-quality emulsions with higher emulsifying activity index (UAE 20.73 m2·g−1, HPH 11.76 m2·g−1 and HSH 6.80 m2·g−1), whiteness (UAE 81.05, HPH 80.67 and HSH 74.09), viscosity coefficient (UAE 0.44 Pa·sn, HPH 0.49 Pa·sn and HSH 0.22 Pa·sn), macroscopic viscosity index (UAE 2.31 nm−2·s, HPH 0.38 nm−2·s and HSH 0.34 nm−2·s), and storage stability, especially for the UAE. Furthermore, UAE was a more efficient emulsification method than HPH to prepare the fine MP-soybean oil emulsion. The protein-coated oil droplets were observed in the three emulsions. The emulsion droplet size of the UAE-fabricated emulsion was the lowest (0.15 μm) while the interfacial protein concentration (93.37%) and the protein exposure extent were the highest among the three emulsions. During the 7 d storage, no separation was observed for the UAE-fabricated emulsion, while the emulsions fabricated by HPH and HSH were separated after storage for 5 d and 2 h. Therefore, this work suggests that UAE could be a better method than HPH and HSH to fabricate MP-soybean oil emulsion.

Generalized hydrodynamics of the Lennard-Jones liquid in view of hidden scale invariance.

In recent years lines along which structure and dynamics are invariant to a good approximation, so-called isomorphs, have been identified in the thermodynamic phase diagrams of several model liquids and solids. This paper reports computer simulation data of the transverse and longitudinal collective dynamics at different length scales along an isomorph of the Lennard-Jones system. Our findings are compared to corresponding results along an isotherm and an isochore. Confirming the theoretical prediction, the reduced-unit dynamics of the transverse momentum density is invariant to a good approximation along the isomorph on all time and length scales. Likewise, the wave-vector dependent shear-stress autocorrelation function is found to be isomorph invariant (with minor deviations at very short times). A similar invariance is not seen along the isotherm or the isochore. Using a spatially nonlocal hydrodynamic model for the transverse momentum-density time-autocorrelation function, the macroscopic shear viscosity and its wave dependence are determined, demonstrating that the shear viscosity is isomorphic invariant on all length scales studied. This analysis implies the existence of a length scale that is isomorph invariant in reduced units, i.e., which characterizes each isomorph. The transverse sound-wave velocity, the Maxwell relaxation time, and the rigidity shear modulus are also isomorph invariant. In contrast to the isomorph invariance of all aspects of the transverse dynamics, the reduced-unit dynamics of the mass density is not invariant on length scales longer than the interparticle distance. By fitting to a generalized hydrodynamic model, we extract values for the wave-vector-dependent thermal diffusion coefficient, sound attenuation coefficient, and adiabatic sound velocity. The isomorph variation of these quantities in reduced units on long length scales can be eliminated by scaling with the density-scaling exponent, a fundamental quantity in the isomorph theory framework; this is an empirical observation that remains to be explained theoretically.

How to best estimate the viscosity of lipid bilayers

The viscosity of lipid bilayers is a property relevant to biological function, as it affects the diffusion of membrane macromolecules. To determine its value, and hence portray the membrane, various literature-reported techniques lead to significantly different results. Herein we compare the results issuing from two widely used techniques to determine the viscosity of membranes: the Fluorescence Lifetime Imaging Microscopy (FLIM), and Fluorescence Recovery After Photobleaching (FRAP). FLIM relates the time of rotation of a molecular rotor inserted into the membrane to the macroscopic viscosity of a fluid. Whereas FRAP measures molecular diffusion coefficients. This approach is based on a hydrodynamic model connecting the mobility of a membrane inclusion to the viscosity of the membrane.We show that:-The first method is very sensitive to local changes in viscosity; however, most often it would only provide the viscosity of the hydrophobic part of the membrane.-The membrane viscosity is adequately estimated when the hydrodynamic model approach is applied to the mobility of micrometric size membrane inclusion but not for nanometric size inclusions such as lipids or proteins. In this case, the calculated value extracted from the same hydrodynamic model characterizes the interaction of the given nano-inclusion with the bilayer instead of the bilayer viscosity.This article emphasizes the pitfalls to be avoided and the rules to be observed in order to obtain a value of the bilayer viscosity that characterizes the bilayer instead of interactions between the bilayer and the embedded probe.

Flows of Linear Polymer Solutions and Other Suspensions of Rod-like Particles: Anisotropic Micropolar-Fluid Theory Approach.

We formulate equations governing flows of suspensions of rod-like particles. Such suspensions include linear polymer solutions, FD-virus, and worm-like micelles. To take into account the particles that form and their rotation, we treat the suspension as a Cosserat continuum and apply the theory of micropolar fluids. Anisotropy of suspensions is determined through the inclusion of the microinertia tensor in the rheological constitutive equations. We check that the model is consistent with the basic principles of thermodynamics. In addition to anisotropy, the theory also captures gradient banding instability, coexistence of isotropic and nematic phases, sustained temporal oscillations of macroscopic viscosity, shear thinning and hysteresis. For the flow between two planes, we also establish that the total flow rate depends not only on the pressure gradient, but on the history of its variation as well.

Effect of ultrasound assisted emulsification in the production of Pickering emulsion formulated with chitosan self-assembled particles: Stability, macro, and micro rheological properties

Chitosan is not a good Pickering emulsion-stabilizer owing to its high hydrophilic properties at low pH. This study prepared chitosan self-assembled particles (pH chitosan = 6.6) stabilized Pickering emulsion by ultrasound assisted emulsification. The effects of ultrasound time on the microstructure, stability, macro and micro rheological properties of the Pickering emulsion were investigated, and the underlying mechanism of emulsion stabilization was also clarified. The chitosan particles were successfully adsorbed on the oil-water interface confirmed by the confocal laser scanning microscope (CLSM). After ultrasound treatment (20 kHz, 300 W, 1, 3, 5, 7, and 9 min), the droplet size and viscosity of the Pickering emulsion decreased. The macroscopic viscosity index (MVI), elasticity index (EI) of the Pickering emulsion decreased with the increase of ultrasound time, while the fluidity index (FI) was reversed. Ultrasound treatment improved the stability of Pickering emulsion observed by the turbiscan stability index (TSI) prior to 5 min. In conclusion, ultrasound assisted emulsification affected the stability of the Pickering emulsion mainly by affecting the particle size and viscosity of the emulsion. The chitosan self-assembled particles stabilized Pickering emulsion prepared by ultrasonic treatment (5 min) stabilized at room temperature at least for 60 days with no delamination.

Peppermint and Myrtle nanoemulsions: Formulation, stability, and antimicrobial activity

Myrtle and Peppermint oil (Myrtus communis and Mentha pulegium) nanoemulsions were formulated using non-ionic surfactant Tween 80 and water through a two-step homogenization process (high-speed homogenizer then high-pressure homogenizer). Physicochemical parameters particularly droplet average diameter, microscopic and macroscopic aspects, pH, viscosity, density, turbidity, refractive index, stability (thermal, physical, and osmotic stability), and antibacterial activity kinetic against E. coli and B. subtilis, have been measured. Obtained results indicate that the formulated nanoemulsions displayed an average droplet diameter inferior to 101 nm and comparable physicochemical characteristics. Considering their stability, Peppermint and Myrtle nanoemulsions exhibited suitable stability under pH, thermal (droplet size comprised between 80 and 1351 nm), and ionic stress as well as after 22 days of storage at 4 °C (average droplet diameter comprised between 90 and 188 nm). Concerning inhibition of bacterial growth, antibacterial activity against E. coli and B. subtilis revealed a marked efficacy particularly against E. coli (Peppermint nanoemulsions reached 99% of growth inhibition), and that efficiency was well kept even upon 22 days of storage at 4 °C. These results may establish the promising interest in Myrtle and peppermint essential oils for the food industry using nanoemulsion-based delivery systems.

Effect of degree of hydrolysis of polyacrylamide on the micromorphology of its solution

AbstractThe properties of polyacrylamide for oil displacement are determined by the microstructure. Optimizing the method of studying the microstructure of polyacrylamide is convenient to screen out the oil displacement polymer with better performance in practice. In this paper, the effects of the degree of hydrolysis on the macroscopic viscosity and micromolecular morphology of polyacrylamide were investigated by using a new method of laser scanning fluorescence microscopy, atomic force microscopy, and cryo‐etching transmission electron microscopy. In the experiment, the influence of alkali content on the dynamic viscosity and micromorphology of the solution was eliminated by the innovative method of dialysis and alkali removal, which ensured the degree of hydrolysis as a single variable. The results show that the dynamic viscosity is less affected by the degree of hydrolysis macroscopically. With the increase of the degree of hydrolysis, the streamline structure of the molecule changed from coarse branched cluster to fluffy line. The chances of intermolecular entanglement are increased during the transformation process, which makes the microstructure characteristics agree with the results that the viscosity changes slightly with the degree of hydrolysis after alkali removal.

Effect of surface charge density of bacterial cellulose nanofibrils on the rheology property of O/W Pickering emulsions

In this study, the effect of surface charge density of bacterial cellulose nanofibrils (BCNF) on the rheological characteristics of O/W Pickering emulsions was investigated by regulating the fibril charge density. BCNFs with different carboxylate group contents (0.66, 0.90 and 1.16 mmol/g dry cellulose, representing as TOBC-a, -b, and -c) were obtained by 2,2,6,6-tetramethylpiperidine-nitrogen-oxide (TEMPO) oxidation. These oxidized products were used as Pickering stabilizers to prepare O/W Pickering emulsions. Diffusing wave spectroscopy (DWS)-based microrheology was utilized to reflect the rheological features of emulsions. TOBC-a stabilized emulsion had a lower macroscopic viscosity, lower elasticity, and better fluidity. It was because a weaker fiber network was formed in the continuous phase during the ultrasonication emulsification. The influences of pH and ionic strength on the rheological properties of high-charged TOBC-c stabilized emulsions were also investigated. The emulsion prepared at pH 3.0 exhibited the highest viscosity. It was probably because the inter-fibrils electrostatic repulsion was weakened by the addition of HCl, and the hydrogen bonding interaction became dominant due to the protonation of carbohydrate group. At pH 11, the emulsion viscosity was lowest, which was resulted from the destruction of the intra-fibrils hydrogen bonds. With the NaCl concentration increased, the emulsion viscosity and elasticity increased. It was induced by the fact that the charge shielding effect of NaCl facilitated the formation of a tighter fibrils network in the continuous phase. These results have the potential to provide a guide for developing emulsion-based products with appropriate fluidity to broaden the practical application of emulsion.

Tracking aggregation behaviour and gel properties induced by structural alterations in myofibrillar protein in mirror carp (Cyprinus carpio) under the synergistic effects of pH and heating

The synergistic effect of pH and heating on the structure, aggregation behaviour and gel properties of myofibrillar protein (MP) in mirror carp (Cyprinus carpio) was evaluated. The surface hydrophobicity of the control at pH 5.0 (143.6 ± 0.3 μg) was significantly higher than that of other samples (P < 0.05). Under the same pH conditions, the decrease in total sulfhydryl content of all samples during the heating process demonstrated that covalent/non-covalent cross-linking occurred between proteins due to heat input. Moreover, the decrease in solubility and the increase in turbidity of all samples verified the fact of MP aggregation, and the changes in the elasticity index (EI) and macroscopic viscosity index (MVI) also indicated a decrease in MP fluidity upon heating treatment. Therefore, the aggregation of MP was affected by pH and heating, and the optimal three-dimensional network structure and gel properties could be formed at pH 6.0 and above 70 °C.

Macroscopic Viscosity of Polymer Solutions from the Nanoscale Analysis.

The effective viscosity in polymer solutions probed by diffusion of nanoparticles depends on their size. It is a well-defined function of the probe size, the radius of gyration, mesh size (correlation length), activation energy, and its parameters. As the nanoparticle’s size exceeds the radius of gyration of polymer coils, the effective viscosity approaches its macroscopic limiting value. Here, we apply the equation for effective viscosity in the macroscopic limit to the following polymer solutions: hydroxypropyl cellulose (HPC) in water, polymethylmethacrylate (PMMA) in toluene, and polyacrylonitrile (PAN) in dimethyl sulfoxide (DMSO). We compare them with previous data for PEG/PEO in water and PDMS in ethyl acetate. We determine polymer parameters from the measurements of the macroscopic viscosity in a wide range of average polymer molecular weights (24–300 kg/mol), temperatures (283–303 K), and concentrations (0.005–1.000 g/cm3). In addition, the polydispersity of polymers is taken into account in the appropriate molecular weight averaging functions. We provide the model applicable for the study of nanoscale probe diffusion in polymer solutions and macroscopic characterization of different polymer materials via rheological measurements.

Disentangling Nano- and Macroscopic Viscosities of Aqueous Polymer Solutions Using a Fluorescent Molecular Rotor.

The macroscopic viscosity of polymer solutions in general differs strongly from the viscosity at the nanometer scale, and the relation between the two can be complicated. To investigate this relation, we use a fluorescent molecular rotor that probes the local viscosity of its molecular environment. For a range of chain lengths and concentrations, the dependence of the fluorescence on the macroscopic viscosity is well described by the classical Förster–Hoffmann (FH) equation, but the value of the FH exponent depends on the polymer chain length. We show that all data can be collapsed onto a master curve by plotting the fluorescence versus polymer concentration, which we explain in terms of the characteristic mesh size of the polymer solution. Using known scaling laws for polymers then allows us to quantitatively explain the relation between the FH exponent and the polymer chain length, allowing us to link the nano- to the macroviscosity.

A pore network modelling approach to investigate the interplay between local and Darcy viscosities during the flow of shear-thinning fluids in porous media

During the flow of non-Newtonian fluids in porous media, the relationships between macroscopic quantities are governed by extremely complex microscopic fluid dynamics resulting from solid-fluid interactions. Consequently, the Darcy-scale viscosity exhibited by a shear-thinning fluid depends on the injection velocity, contrarily to the case of Newtonian fluids. In the present work, pore network modelling is used to investigate the relationships between local and macroscopic viscosities during the flow of shear-thinning fluids in 3D porous media. Special efforts are devoted to 1) identifying the influence of the viscosity exhibited by the fluid within the constrictions of the preferential flow paths on the value of Darcy-scale viscosity and 2) proposing an analytical expression to upscale viscosity from the local viscosity values. To go further, the reduction in average hydraulic tortuosity stemming from the directional nature of shear-thinning behavior in 3D porous media will also be quantified. The results of the present study show that Darcy-scale viscosity can be accurately calculated as the flow-rate weighted average of local viscosities in the investigated media. Moreover, the velocity maps provided by the proposed pore network flow simulations are suitable to assess hydraulic tortuosity reduction as compared to the flow of a Newtonian fluid.

Organic Acid-Enhanced Viscoelastic Surfactant and Its Application in Fracturing Fluids

Viscoelastic surfactant (VES) fracturing fluids, with the advantages of low residues, complete gel breaking, and low formation damage, have received considerable attention in hydraulic fracturing techniques. However, the complicated synthesis process and high costs limit the widespread application of VESs. Herein, a VES fracturing fluid composed of wormlike micelles was developed by coupling an ultralong hydrophobic chain surfactant N-erucamidopropyl-N,N-dimethylamine (EA), with p-phthalic acid (p-PA), which behaved as a “Gemini-like” surfactant via noncovalent interactions. The macroscopic appearance and viscosity of this fluid were responsive to the regulation of pH values. Then, the related fracturing performance of this fluid was systematically investigated, from which it could be concluded that the VES fluid exhibited good temperature and shear resistance, excellent proppant-carrying and gel-breaking abilities and also caused less damage to core permeability and low corrosion of steel under acidic conditions. Finally, the rheological properties of the VES fluid could be switched multiple times without any decay by changing the pH values, indicating its excellent reusability for fracturing procedures. Consequently, this study demonstrates potential applications of reusable VES fracturing fluids based on supramolecular pH-responsive surfactants.

Towards a general understanding of the effects of hydrophobic additives on the viscosity of surfactant solutions

Small amounts of nonpolar additives can have a tremendous impact on viscosity and viscoelasticity of giant micelles and completely change macroscopic properties. The effect can be best understood with the establishment of complete salt curves by screening surfactant viscosity as a function of electrolyte concentration. From previous studies in micellar systems of sodium laureth sulfate (SLES) with fragrance molecules, two independent mechanisms could be identified, co-solvent type interactions leading to a decrease of the maximum viscosity, and co-surfactant type interactions that cause the salt curve shift to the left. Our studies here reveal two new mechanisms with different effects on the salt curve. In particular, with long-chain hydrocarbons from n-octane to n-tetradecane a right shift was observed, whereas with short-chain or cyclic hydrocarbons such as n-hexane or cyclohexane the maximum viscosity increases. The two effects are interpreted via an extension of a recently developed thermodynamic model where changes in viscosity can be rationalized by a rebalance of the relative concentration of the three co-existing microphases: endcaps, cylinders and branching points. The right shift is linked to a continuous transformation of giant micelles into microemulsions containing an internal fluid. On the other hand, viscosity at maximum scales with the generalized bending constant of the molecular film forming the three microphases of the surfactant system. The total of four proposed mechanisms of solute-surfactant interactions that can impact amplitude and position of salt curves are independent and of different origin, but they are all intimately linked to the location of the additives within the surfactant film: headgroup, micellar interface, surfactant tail region or micellar core. Further investigation will be necessary to understand the molecular driving forces that position nonpolar additives within micellar aggregates, which would be the key for successful prediction of their impact on macroscopic viscosity.