Immersed Boundary Simulations of Active Fluid Droplets

Whitfield, Carl A.; Hawkins, Rhoda J.

doi:10.1371/journal.pone.0162474

Cited by 7 publications

(7 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Interestingly, we are also able to obtain an oscillatory state without any built-in dynamical oscillator in our model. This oscillatory behaviour is also observed in simple models of cell crawling [12] and actin cortex [34]. This illustrates how simple physical mechanisms can give rise to oscillatory behaviour in biological systems without the need of an internal chemical oscillator.…”

Section: Discussionsupporting

confidence: 57%

Contractile and chiral activities codetermine the helicity of swimming droplet trajectories

Tjhung

Cates

Marenduzzo

2017

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Active fluids are a class of nonequilibrium systems where energy is injected into the system continuously by the constituent particles themselves. Many examples, such as bacterial suspensions and actomyosin networks, are intrinsically chiral at a local scale, so that their activity involves torque dipoles alongside the force dipoles usually considered. Although many aspects of active fluids have been studied, the effects of chirality on them are much less known. Here, we study by computer simulation the dynamics of an unstructured droplet of chiral active fluid in three dimensions. Our model considers only the simplest possible combination of chiral and achiral active stresses, yet this leads to an unprecedented range of complex motilities, including oscillatory swimming, helical swimming, and run-and-tumble motion. Strikingly, whereas the chirality of helical swimming is the same as the microscopic chirality of torque dipoles in one regime, the two are opposite in another. Some of the features of these motility modes resemble those of some single-celled protozoa, suggesting that underlying mechanisms may be shared by some biological systems and synthetic active droplets.

show abstract

Section: Discussionsupporting

confidence: 57%

Contractile and chiral activities codetermine the helicity of swimming droplet trajectories

Tjhung

Cates

Marenduzzo

2017

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Our analytical calculations do not predict this as we assume a form for the r-dependence of the polarisation such that it is strongly coupled to the curvature. This behaviour goes beyond the scope of the analytical work here as this corresponds to a transition to an 'active turbulence' state, as numerically simulated in [29].…”

Section: Results and Comparison With Simulationsmentioning

confidence: 88%

“…We test these analytical results against the 2D simulations developed in [28]. These use an Immersed Boundary method [35,36] to represent the active interface explicitly as a Lagrangian mesh which is coupled to the Cartesian mesh for the 2D fluid via a numerical Dirac delta function.…”

Section: Results and Comparison With Simulationsmentioning

confidence: 99%

See 1 more Smart Citation

Instabilities, motion and deformation of active fluid droplets

Whitfield

Hawkins

2016

New J. Phys.

View full text Add to dashboard Cite

We consider two minimal models of active fluid droplets that exhibit complex dynamics including steady motion, deformation, rotation and oscillating motion. First we consider a droplet with a concentration of active contractile matter adsorbed to its boundary. We analytically predict activity driven instabilities in the concentration profile, and compare them to the dynamics we find from simulations. Secondly, we consider a droplet of active polar fluid of constant concentration. In this system we predict, motion and deformation of the droplets in certain activity ranges due to instabilities in the polarisation field. Both these systems show spontaneous transitions to motility and deformation which resemble dynamics of the cell cytoskeleton in animal cells.

show abstract

“…To obtain actual shape predictions, a number of works start instead from a parametrized, free membrane shape which is adjusted so as to fulfill the force balance equations for a given set of parameters and boundary conditions. This procedure can be carried out either analytically [3,43] or numerically [15,20,21,[44][45][46]. For example, Berthoumieux et al [3] derived Green's functions to predict the deformation of an infinitely long cylindrical active, elastic membrane resulting from the application of a point active stress.…”

Section: Introductionmentioning

confidence: 99%

Computational modeling of active deformable membranes embedded in three-dimensional flows

Bächer

Gekle

2019

Phys. Rev. E

View full text Add to dashboard Cite

Active gel theory has recently been very successful in describing biologically active materials such as actin filaments or moving bacteria in temporally fixed and simple geometries such as cubes or spheres. Here we develop a computational algorithm to compute the dynamic evolution of an arbitrarily shaped, deformable thin membrane of active material embedded in a 3D flowing liquid. For this, our algorithm combines active gel theory with the classical theory of thin elastic shells. To compute the actual forces resulting from active stresses, we apply a parabolic fitting procedure to the triangulated membrane surface. Active forces are then dynamically coupled via an Immersed-Boundary method to the surrounding fluid whose dynamics can be solved by any standard, e.g. Lattice-Boltzmann, flow solver. We validate our algorithm using the Green's functions of [Berthoumieux et al. New J. Phys. 16, 065005 (2014)] for an active cylindrical membrane subjected (i) to a locally increased active stress and (ii) to a homogeneous active stress. For the latter scenario, we predict in addition a so far unobserved non-axisymmetric instability. We highlight the versatility of our method by analyzing the flow field inside an actively deforming cell embedded in external shear flow. Further applications may be cytoplasmic streaming or active membranes in blood flows. Published as: Phys. Rev. E 99(6), 062418 (2019)

show abstract

Immersed Boundary Simulations of Active Fluid Droplets

Cited by 7 publications

References 45 publications

Contractile and chiral activities codetermine the helicity of swimming droplet trajectories

Contractile and chiral activities codetermine the helicity of swimming droplet trajectories

Instabilities, motion and deformation of active fluid droplets

Computational modeling of active deformable membranes embedded in three-dimensional flows

Contact Info

Product

Resources

About