Thermoelectric Properties of Fe0.2Co3.8Sb12-xTex ... - Physics

Single-particle and collective behaviour of
colloidal swimmers
Suropriya Saha, Sriram Ramaswamy, Ramin Golestanian
November 16, 2012
Colloidal particles with a catalytic region on their surface, when immersed in
areactantsolution,generateachemicalgradientintheirownvicinity[1],anduse
the resulting anisotropic stresses to propel themselves through the mechanism of
diffusiophoresis. We have have shown that polar active particles of this type can
alsoorientthemselvesalonganimposedgradientofreactantconcentration. This
amounts to a theoretical demonstration of a phoretic analogue of chemotaxis,
that is, the ability of a self-propelled particle to align with respect to, and hence
to move up or down, a chemical gradient. The nature of the chemotaxis depends
on the shape of the particle, on the distribution of enzymatic sites on its surface,
and on the surface mobility. We have also shown that a collection of these
particles when supplied with reactants at a steady rate can interact through
their long ranged diffusion fields to produce clumping or patterning instabilities.
We have studied these instabilities by looking at the mode structure and the
structure factor in different limits – abundant or meagre supply of reactants and
slow or fast reaction dynamics.
References
[1] R. Golestanian, T. B. Liverpool and A. Ajdari, Phys. Rev. Lett. 94, 220801
(2005)
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