The present invention provides an improved method and device for preparing, extracting, separating and/or purifying a biomolecule, for example, nucleic acid from a biological sample. The device comprises a heat-deformable material, such that an inner chamber adopts a second configuration having a chamber volume less than the chamber volume of a first configuration, thereby expelling at least a part of a processed sample through a second opening from the device, and thereby recovering the biomolecule-containing composition.