Undulatory swimming in shear-thinning fluids: experiments withCaenorhabditis elegans

Abstract

The swimming behaviour of microorganisms can be strongly influenced by the rheology of their fluid environment. In this manuscript, we experimentally investigate the effects of shear-thinning viscosity on the swimming behaviour of an undulatory swimmer, the nematode Caenorhabditis elegans. Tracking methods are used to measure the swimmer's kinematic data (including propulsion speed) and velocity fields. We find that shear-thinning viscosity modifies the velocity fields produced by the swimming nematode but does not modify the nematode's speed and beating kinematics. Velocimetry data show significant enhancement in local vorticity and circulation, and an increase in fluid velocity near the nematode's tail, compared to Newtonian fluids of similar effective viscosity. These findings are compared to recent theoretical and numerical results. * parratia@seas.upenn.edu arXiv:1407.5854v2 [physics.flu-dyn]

Flow analysis of the low Reynolds number swimmerC. elegans

“…Recently C. elegans has been used extensively as a model system for experimental studies of propulsion, particularly at low Reynolds number, due to its simple planar swimming gait and size [9][10][11][12][13][14][15]. The nematode generates planar bending waves through contractions of its ventral and dorsal muscles, producing a quasi-two-dimensional (2D) traveling sine wave along its body [10,16,17].…”

“…At around 1 mm in length and 75 μm in diameter, C. elegans is significantly larger than the majority of low-Re undulatory swimmers, enabling high-resolution reconstruction and analysis of planar flow fields from particle tracking data. The resulting flow fields can be used to probe properties of both the swimmer and fluid, providing new insights into the physics of undulatory propulsion [11][12][13][14][15][18][19][20]. However, despite exhibiting a planar swimming stroke, the flow around C. elegans has a complex three-dimensional structure ( Fig.…”

The bearable gooeyness of swimming

“…Like many thought-provoking experiments, the study by Gagnon et al (2014) leads to more questions than answers. The worms are self-propelled, and it is the balance between waving propulsion and drag that leads to their swimming speed (Lauga & Powers 2009).…”

“…Overview Gagnon et al (2014) consider the locomotion of the millimetre-sized nematode C. elegans in a variety of shear-thinning fluids (figure 1a). They measure the locomotion kinematics and the fluid mechanisms around the organism using tracer particles for two kinds of fluids: (a) solutions of the rod-like polymer xanthan gum, which show rheological data consistent with a Carreau fluid with power indices n ranging from 0.3 to 0.9 (i.e.…”

Following fluctuating signs: Anomalous active superdiffusion of swimmers in anisotropic media

“…Examples range from the motion of cilia and spermatozoa in mucus [8,9] to bacteria in the host tissue [10] and nematodes migrating though soil [11]. Recent efforts aimed at gaining a better understanding of the role of the complex environment involve studying microswimming in non-Newtonian solvents such as viscoelastic fluids [6,[12][13][14][15][16][17][18][19][20], in liquid crystalline environments [19,[21][22][23][24][25][26][27], in the presence of random [28] or patterned [29] obstacles, or in crystalline [30][31][32] media.…”