Microfluidic storage device for pre-storing a fluid, comprising: a first polymer substrate, having a first surface in which a laterally extending recess is formed, wherein the first polymer substrate comprises the following: - a first through-hole, - a first auxiliary through-hole, which is formed between the first through-hole and the recess, - a second through-hole, which is arranged opposite the first through-hole in relation to the recess, and - a second auxiliary through-hole, which is formed between the second through-hole and the recess, a second polymer substrate, having a second surface which is essentially formed so as to match the first surface with a form fit at least in subregions outside the recess, wherein a first channel and a second channel are formed in the second surface of the second polymer substrate, and an elastic polymer membrane which is arranged between the first and second polymer substrates (20, 40), is in contact with the first and second surfaces (21, 41) in regions outside the recess and, in the region of the recess, can essentially line the latter so that the volume region inside the recess, between the polymer membrane and the second polymer substrate, can be filled with the fluid, wherein, the second surface of the second polymer substrate is applied onto the first surface of the first polymer substrate with the polymer membrane arranged between them, such that the first channel connects together the region which is arranged in the second surface in extension of the first through-hole, the region which is arranged in the second surface in extension of the first auxiliary through-hole, and a closely lying first region which is arranged in the second surface, facing a subregion of the recess, and the second channel connects together the region which is arranged in the second surface in extension of the second through-hole, the region which is arranged in the second surface in extension of the second auxiliary through-hole, and a closely lying second region which is arranged in the second surface, facing a subregion of the recess, wherein the first polymer substrate, the polymer membrane and the second polymer substrate can be joined to one another at least in subregions, outside the recess, in which the polymer membrane is in contact with the first and second surfaces (21, 41), and wherein the polymer membrane can be joined to the wall of the first or second channel (42, 44) in the regions of the first or second auxiliary through-hole (25, 28) which can be brought into contact with the wall of the first or second channel (42, 44). a first polymer substrate, having a first surface in which a laterally extending recess is formed, wherein the first polymer substrate comprises the following: - a first through-hole, - a first auxiliary through-hole, which is formed between the first through-hole and the recess, - a second through-hole, which is arranged opposite the first through-hole in relation to the recess, and - a second auxiliary through-hole, which is formed between the second through-hole and the recess, - a first through-hole, - a first auxiliary through-hole, which is formed between the first through-hole and the recess, - a second through-hole, which is arranged opposite the first through-hole in relation to the recess, and - a second auxiliary through-hole, which is formed between the second through-hole and the recess, a second polymer substrate, having a second surface which is essentially formed so as to match the first surface with a form fit at least in subregions outside the recess, wherein a first channel and a second channel are formed in the second surface of the second polymer substrate, and an elastic polymer membrane which is arranged between the first and second polymer substrates (20, 40), is in contact with the first and second surfaces (21, 41) in regions outside the recess and, in the region of the recess, can essentially line the latter so that the volume region inside the recess, between the polymer membrane and the second polymer substrate, can be filled with the fluid, wherein, the second surface of the second polymer substrate is applied onto the first surface of the first polymer substrate with the polymer membrane arranged between them, such that the first channel connects together the region which is arranged in the second surface in extension of the first through-hole, the region which is arranged in the second surface in extension of the first auxiliary through-hole, and a closely lying first region which is arranged in the second surface, facing a subregion of the recess, and the second channel connects together the region which is arranged in the second surface in extension of the second through-hole, the region which is arranged in the second surface in extension of the second auxiliary through-hole, and a closely lying second region which is arranged in the second surface, facing a subregion of the recess, wherein the first polymer substrate, the polymer membrane and the second polymer substrate can be joined to one another at least in subregions, outside the recess, in which the polymer membrane is in contact with the first and second surfaces (21, 41), and wherein the polymer membrane can be joined to the wall of the first or second channel (42, 44) in the regions of the first or second auxiliary through-hole (25, 28) which can be brought into contact with the wall of the first or second channel (42, 44).