Modeling microscopic swimmers at low Reynolds number

Abstract

The authors employ three numerical methods to explore the motion of low Reynolds number swimmers, modeling the hydrodynamic interactions by means of the Oseen tensor approximation, lattice Boltzmann simulations, and multiparticle collision dynamics. By applying the methods to a three bead linear swimmer, for which exact results are known, the authors are able to compare and assess the effectiveness of the different approaches. They then propose a new class of low Reynolds number swimmers, generalized three bead swimmers that can change both the length of their arms and the angle between them. Hence they suggest a design for a microstructure capable of moving in three dimensions. They discuss multiple bead, linear microstructures and show that they are highly efficient swimmers. They then turn to consider the swimming motion of elastic filaments. Using multiparticle collision dynamics the authors show that a driven filament behaves in a qualitatively similar way to the micron-scale swimming device recently demonstrated by Dreyfus et al. [Nature (London) 437, 862 (2005)].

Hydrodynamic correlations in multiparticle collision dynamics fluids

“…Similar nonequilibrium properties have been studied for colloids [7,[20][21][22][23][24][25][26], polymers [19,[27][28][29][30][31][32][33][34], vesicles [35], and cells [36,37] in flow fields, colloids in viscoelastic fluids [38], as well as for self-propelled spheres [39][40][41], rods [3,42], and other swimming objects [43][44][45]. Moreover, extensions have been proposed for fluids with nonideal equations of state [46] and mixtures [47].…”

Towards active microfluidics: Interface turbulence in thin liquid films with floating molecular machines

“…Equations (7,8) were integrated using the semi-implicit method (see appendix B) for a one-dimensional system using periodic boundary conditions. As the initial condition, the flat interface with a uniform machine distribution was chosen and small random initial perturbations were applied.…”

“…Generally, it can be shown that any physical object, cyclically changing its shape in such a way that the internal forward and back motions are different, propels itself through the liquid [3,4]. Elementary models of such swimmers, constructed by joining together mobile links [3,5] or by connecting a few spheres by several actively deformable links [6,7,8], have been considered. Typically, the concept of molecular swimmers is applied to explain active motion of bacteria and other microorganisms.…”

On the self-propulsion of an -sphere micro-robot

“…Studies of micro-robots represent a flourishing modern research topic that strives to create a fundamental base for modern applications in medicine and technology, see Purcell (1977), Becker, Koelher & Ryder (2003), Najafi & Golestanian (2004), Dreyfus et al (2005), Chang et al (2007), Earl et al (2007), Alouges, DeSimone & Lefebvre (2008), Golestanian & Ajdari (2008, 2009, Leoni et al (2009), Alexander, Pooley & Yeomans (2009), Gilbert et al (2010) and Lauga (2011). The simplicity of the geometry represents the major advantage in studies of micro-robots (in contrast with the extreme complexity of self-swimming micro-organisms, e.g.…”