Lattice Boltzmann simulations of soft matter systems

This article concerns numerical simulations of the dynamics of particles immersed in a continuum solvent. As prototypical systems, we consider colloidal dispersions of spherical particles and solutions of uncharged polymers. After a brief explanation of the concept of hydrodynamic interactions, we give a general overview over the various simulation methods that have been developed to cope with the resulting computational problems. We then focus on the approach we have developed, which couples a system of particles to a lattice Boltzmann model representing the solvent degrees of freedom. The standard D3Q19 lattice Boltzmann model is derived and explained in depth, followed by a detailed discussion of complementary methods for the coupling of solvent and solute. Colloidal dispersions are best described in terms of extended particles with appropriate boundary conditions at the surfaces, while particles with internal degrees of freedom are easier to simulate as an arrangement of mass points with frictional coupling to the solvent. In both cases, particular care has been taken to simulate thermal fluctuations in a consistent way. The usefulness of this methodology is illustrated by studies from our own research, where the dynamics of colloidal and polymeric systems has been investigated in both equilibrium and nonequilibrium situations.Comment: Review article, submitted to Advances in Polymer Science. 16 figures, 76 page

What to Buy? On the Complexity of Being a Critical Consumer

This article criticises the notion that critical/political/ethical consumerism can solve issues related to sustainability and food production. It does this by analysing the complexity of the concept of sustainability as related to food choices. The current trend of pursuing a sustainable food production through critical purchase decisions rather than through regulation is shown to be problematic, as shopping for a more sustainable food system might be much harder than initially believed due to the conflicting values and inherent trade-offs entailed in the different notions of sustainability. Thus, critical consumerism may give way to false expectations as the complexity of choices transpires. One obvious way out is to let decisions regarding food choices be made earlier in the food production chain as well as through new modes of governance engaging members of civil society in their capacity as citizens rather than consumers. This entails complementing society’s reliance on critical consumerism with a citizen-oriented and political process in support of making more sustainable food choices