The invention concerns a method for isolating an analyte (1) from an initial sample containing same, on a reactive surface (9) in contact with all or part of the initial sample, characterized in that it comprises the following steps which consist in: 1) forming and/or maintaining a reaction volume entity (2), comprising an internal liquid medium (4), corresponding to all or part of the initial sample, the entity (2) including an interface (5) with an external medium (6), having with the latter a surface tension; 2) applying a temperature difference between at least two thermal points located: a) proximate to and/or b) on the surface and/or c) within said entity (2), said thermal points being respectively different, in terms of temperature and positioning; 3) fixing the analyte (1) on the reactive surface (9), positioned on the path of forced convection generated by the temperature difference.