Pearling, wrinkling, and buckling of vesicles in elongational flows

Narsimhan, Vivek; Spann, Andrew; Shaqfeh, Eric S. G.

doi:10.1017/jfm.2015.345

Cited by 44 publications

(65 citation statements)

References 36 publications

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“…61-63 Interestingly, recent theory for pearling suggests that pearling only occurs for reduced volumes ν < 0.6. 64 We observed pearling of every tether following asymmetric dumbbell formation, including vesicles with ν > 0.6, once the tether reached a certain length. Possibly there are important factors not considered in the modeling work, such as membrane thermal fluctuations.…”

Section: Discussionmentioning

confidence: 72%

Experimental observation of the asymmetric instability of intermediate-reduced-volume vesicles in extensional flow

et al. 2016

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Vesicles provide an attractive model system to understand the deformation of living cells in response to mechanical forces. These simple, enclosed lipid bilayer membranes are suitable for complementary theoretical, numerical, and experimental analysis. A recent study [Narsimhan, Spann, Shaqfeh, Journal of Fluid Mechanics, 2014, 750, 144] predicted that intermediate-aspect-ratio vesicles extend asymmetrically in extensional flow. Upon infinitesimal perturbation to the vesicle shape, the vesicle stretches into an asymmetric dumbbell with a cylindrical thread separating the two ends. While the symmetric stretching of high-aspect-ratio vesicles in extensional flow has been observed and characterized [Kantsler, Segre, Steinberg, Physics Review Letters, 2008, 101, 048101] as well as recapitulated in numerical simulations by Narsimhan et al., experimental observation of the asymmetric stretching has not been reported. In this work, we present results from microfluidic cross-slot experiments observing this instability, along with careful characterization of the flow field, vesicle shape, and vesicle bending modulus. The onset of this shape transition depends on two non-dimensional parameters: reduced volume (a measure of vesicle asphericity) and capillary number (ratio of viscous to bending forces). We observed that every intermediate-reduced-volume vesicle that extends forms a dumbbell shape that is indeed asymmetric. For the subset of the intermediate-reduced-volume regime we could capture experimentally, we present an experimental phase diagram for asymmetric vesicle stretching that is consistent with the predictions of Narsimhan et al.

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Section: Discussionmentioning

confidence: 72%

Experimental observation of the asymmetric instability of intermediate-reduced-volume vesicles in extensional flow

et al. 2016

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“…From this view, such studies can inform how the fluid dynamics and membrane properties inside and outside the fluid-filled compartment contribute to cell shape changes. From this view, a significant amount of prior work has been focused on investigating the shape dynamics of vesicles under different flow conditions, such as Poiseuille flow [8][9][10], shear flow [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], and extensional flow [26][27][28][29][30][31][32]. Experiments and simulations on vesicles * To whom correspondence must be addressed: cms@illinois.edu in shear flow have uncovered intriguing dynamic behavior including: (i) tumbling, where a vesicle undergoes a periodic flipping motion, (ii) trembling, where vesicle shape fluctuates and the orientation oscillates in time, and (iii) tank-treading, where an ellipsoid vesicle's major axis maintains a fixed orientation with respect to the flow direction while the membrane rotates about the vorticity axis [11,18,21,23].…”

Section: Introductionmentioning

confidence: 99%

Conformational dynamics and phase behavior of lipid vesicles in a precisely controlled extensional flow

2020

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Lipid vesicles play a key role in fundamental biological processes. Despite recent progress, we lack a complete understanding of the non-equilibrium dynamics of vesicles due to challenges associated with long-time observation of shape fluctuations in strong flows. In this work, we present a flowphase diagram for vesicle shape and conformational transitions in planar extensional flow using a Stokes trap, which enables control over the center-of-mass position of single or multiple vesicles in precisely defined flows [Shenoy, Rao, Schroeder, PNAS, 113(15):3976-3981, 2016]. In this way, we directly observe the non-equilibrium conformations of lipid vesicles as a function of reduced volume ν, capillary number Ca, and viscosity contrast λ. Our results show that vesicle dynamics in extensional flow are characterized by the emergence of three distinct shape transitions, including a tubular to symmetric dumbbell transition, a spheroid to asymmetric dumbbell transition, and quasi-spherical to ellipsoid transition. The experimental phase diagram is in good agreement with recent predictions from simulations [Narsimhan, Spann, Shaqfeh, J. Fluid Mech., 2014, 750, 144]. We further show that the phase boundary of vesicle shape transitions is independent of the viscosity contrast. Taken together, our results demonstrate the utility of the Stokes trap for the precise quantification of vesicle stretching dynamics in precisely defined flows.

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“…Moreover, the dilational surface viscosity has not been taken into account. The calculation of the dynamics of pearling instability along tubular vesicles Boedec, Jaeger & Leonetti (2014) has been recently improved by taking into account the shear surface viscosity (Narsimhan, Spann & Shaqfeh 2015). Here, the study is focused on droplets considering both the dilational and shear viscosities to better understand their respective contributions on shape dynamics of soft particles such as droplets.…”

Section: Introductionmentioning

confidence: 99%

Influence of surface viscosity on droplets in shear flow

et al. 2016

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The behaviour of a single droplet in an immiscible external fluid, submitted to shear flow is investigated using numerical simulations. The surface of the droplet is modelled by a Boussinesq-Scriven constitutive law involving the interfacial viscosities and a constant surface tension. A numerical method using Loop subdivision surfaces to represent droplet interface is introduced. This method couples boundary element method for fluid flows and finite element method to take into account the stresses due to the surface dilational and shear viscosities and surface tension. Validation of the numerical scheme with respect to previous analytic and computational work is provided, with particular attention to the viscosity contrast and the shear and dilational viscosities characterized both by a Boussinesq number B q . Then, influence of equal surface viscosities on steady-state characteristics of a droplet in shear flow are studied, considering both small and large deformations and for a large range of bulk viscosity contrast. We find that small deformation analysis is surprisingly predictive at moderate and high surface viscosities. Equal surface viscosities decrease the Taylor deformation parameter and tank-treading angle and also strongly modify the dynamics of the droplet: when the Boussinesq number (surface viscosity) is large relative to the capillary number (surface tension), the droplet displays damped oscillations prior to steady-state tank-treading, reminiscent from the behaviour at large viscosity contrast. In the limit of infinite capillary number Ca, such oscillations are permanent. The influence of surface viscosities on breakup is also investigated, and results show that the critical capillary number is increased. A diagram (B q ; Ca) of breakup is established with the same inner and outer bulk viscosities. Additionally, the separate roles of shear and dilational surface viscosity are also elucidated, extending results from small deformation analysis. Indeed, shear (dilational) surface viscosity increases (decreases) the stability of drops to breakup under shear flow. The steady-state deformation (Taylor parameter) varies nonlinearly with each Boussinesq number or a linear combination of both Boussinesq numbers. Finally, the study shows that for certain combinations of shear and dilational viscosities, drop deformation for a given capillary number is the same as in the case of a clean surface while the inclination angle varies.

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Pearling, wrinkling, and buckling of vesicles in elongational flows

Cited by 44 publications

References 36 publications

Experimental observation of the asymmetric instability of intermediate-reduced-volume vesicles in extensional flow

Experimental observation of the asymmetric instability of intermediate-reduced-volume vesicles in extensional flow

Conformational dynamics and phase behavior of lipid vesicles in a precisely controlled extensional flow

Influence of surface viscosity on droplets in shear flow

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