--- res: bibo_abstract: - 'Diffusiophoretic motion of colloids and macromolecules under salt gradients exhibits a logarithmic-sensing, i.e. the particle velocity is proportional to the spatial gradient of the logarithm of the salt concentration, as VDP = DDP∇logc. Here we explore experimentally the implications of this log-sensing behavior, on the basis of a hydrogel microfluidic device allowing to build spatially and temporally controlled gradients. We first demonstrate that the non-linearity of the salt-taxis leads to a trapping of particles under concentration gradient oscillations via a rectification of the motion. As an alternative, we make use of the high sensitivity of diffusiophoretic migration to vanishing salt concentration due to the log-sensing: in a counter-intuitive way, a vanishing gradient can lead to measurable velocity provided that the solute concentration is low enough, thus keeping ∇c/c finite. We show that this leads to a strong segregation of particles in osmotic shock configuration, resulting from a step change of the salt concentration at the boundaries. These various phenomena are rationalized on the basis of a theoretical description for the time-dependent Smoluchowski equation for the colloidal density.@eng' bibo_authorlist: - foaf_Person: foaf_givenName: Jérémie A foaf_name: Palacci, Jérémie A foaf_surname: Palacci foaf_workInfoHomepage: http://www.librecat.org/personId=8fb92548-2b22-11eb-b7c1-a3f0d08d7c7d orcid: 0000-0002-7253-9465 - foaf_Person: foaf_givenName: Cécile foaf_name: Cottin-Bizonne, Cécile foaf_surname: Cottin-Bizonne - foaf_Person: foaf_givenName: Christophe foaf_name: Ybert, Christophe foaf_surname: Ybert - foaf_Person: foaf_givenName: Lydéric foaf_name: Bocquet, Lydéric foaf_surname: Bocquet bibo_doi: 10.1039/c1sm06395b bibo_issue: '4' bibo_volume: 8 dct_date: 2012^xs_gYear dct_isPartOf: - http://id.crossref.org/issn/1744-683X - http://id.crossref.org/issn/1744-6848 dct_language: eng dct_publisher: Royal Society of Chemistry@ dct_title: Osmotic traps for colloids and macromolecules based on logarithmic sensing in salt taxis@ ...