The present invention relates to a magnetic stirrer for stirring or mixing biological fluids, such as blood.

A typical known magnetic stirrer is a cross, comprising at lest one magnetic bar, to be placed into a vessel containing a fluid to mix. A magnetic motor outside of the vessel is placed in the vicinity of the cross, for coupling with the cross and imposing a rotational movement to the cross, and thereby mixing the fluid.

If the fluid presents a high viscosity, such as blood, the mixing may not be effective, especially if the sample in the vessel presents a height significantly greater than the height of the cross. The mixing in such a case may require a significant amount of time, and it might even be impossible to mix the entire sample in such conditions (high viscosity and/or great height of the sample).

The present invention aims to solve these aforementioned drawbacks and is first directed to propose a magnetic stirrer which allows an effective mixing of a complete liquid sample, even if the sample presents a high viscosity or a great height.

With this goal in mind, a first aspect of the invention is a magnetic stirrer for mixing a liquid sample contained in a vessel, comprising:

- at least one magnetic portion arranged to be placed into the vessel and arranged to be coupled to a magnetic motor arranged outside of the vessel, for stirring the liquid sample within a first space of the vessel,

- one elevated portion arranged to mix the liquid sample in a second space of the vessel, distinct from the first space,

- a connecting portion arranged to attach the elevated portion to the at least one magnetic portion, characterized in that the connecting portion is arranged to effectively stir the liquid sample in a third space of the vessel, located between the first space and the second space. The magnetic stirrer according to the invention presents three portions, each designed to mix the fluid in a specific space/area of the liquid sample. With this design, the liquid sample is effectively stirred by the magnetic portion, the connecting portion and the elevated portion. By stirring the liquid sample, it is meant the liquid sample is locally agitated and/or shaken by a portion of the magnetic stirrer. This means that even if the liquid sample is viscous, it will be mixed, as there will be a portion of the magnetic stirrer which will provoke local movements into the liquid sample all along its height in the vessel.

Advantageously, the connecting portion presents at least one eccentric portion being off-centered relatively to an axis of rotation of the magnetic stirrer. The off-centered portion will provoke local movements within the liquid sample during the rotation of the magnetic stirrer, leading to an effective mixing. Movements in the fluid may be random, similar to turbulent flows near the magnetic stirrer, leading to an effective mixing.

Advantageously, the connecting portion presents at least one cross section with a width in a first direction and a length in a second direction different from the first direction, the width being smaller or equal to an half of the length. The connecting portion may be a wall, with a cross section in a rectangle shape, or an oval shape.

Advantageously, the connecting portion comprises at least one leg connecting the at least one magnetic portion to the elevated portion, at a periphery of the magnetic portion. The arrangement at the periphery ensures a mixing even at a significant distance of the rotation axis.

Advantageously, the at least one magnetic portion is a magnetic cross with two crossed bars, and the connecting portion comprises two legs each coupled to the magnetic cross at one of the extremities of one of the two crossed bars. Advantageously, the connecting portion is snap fitted onto the magnetic portion. This snap fit coupling allows easy set up of the magnetic stirrer.

Advantageously, the connecting portion comprises two legs each coupled at one of their extremities to the at least one magnetic portion, and the elevated portion is one transverse beam coupled to the other extremity of each leg.

Advantageously, each leg is snap fitted to the at least one magnetic portion. Advantageously, the transverse beam is snap fitted to the legs.

Advantageously, the magnetic stirrer is integrally molded.

Advantageously, the connecting portion and/or the elevated portion is manufactured or coated with polytetrafluoroethylene (PTFE).

A second aspect of the invention is a kit for assembling a magnetic stirrer according to the first aspect of the invention with a connecting portion being detachable from the magnetic portion and/or from the elevated portion, the kit comprising at least one elevated portion, and at least two different connecting portions, each connecting portion having a specific length, different from the length of the other connecting portion. A third aspect of the invention is a use of a magnetic stirrer to stir a biological sample having a dynamic viscosity equal or greater to 4.10 ^"3 Pa.s and placed in a vessel, wherein the magnetic stirrer comprises:

- at least one magnetic portion arranged to be placed into the vessel and arranged to be coupled to a magnetic motor arranged below the vessel, for stirring the liquid sample within a first space located at a bottom of the vessel,

- one elevated portion arranged above the first space, to mix the liquid sample in a second space above the first space,

- a connecting portion arranged to attach the elevated portion to the at least one magnetic portion. Advantageously, the connecting portion is arranged to stir the biological sample in a third space, located between the first space and second space.

Advantageously, the biological sample is blood. Other characteristics and advantages of the present invention will appear more clearly from the following detailed description of particular non- limitative examples of the invention, illustrated by the appended drawings where:

- Figure 1 represents a magnetic stirrer according to a first embodiment of the invention;

- Figure 2 represents the magnetic stirrer of figure 1 placed in a vessel to mix a biological sample contained in the vessel;

- Figure 3 represents a magnetic stirrer according to a second embodiment of the invention. Figure 1 represents a magnetic stirrer comprising a magnetic portion

10 in a form of a cross with a height H1 , and being a lower part of the magnetic stirrer. The magnetic stirrer comprises an elevated portion 20 with a height H2. As shown on figure 1 , the elevated portion 20 is a bar or a beam being connected to the magnetic portion 10 by two legs 31 , 32 forming a connecting portion 30 with a height H3.

The legs 31 and 32 are arranged at the periphery of the magnetic portion 10, but this is not mandatory to carry out the invention. This embodiment comprises four distinct parts which can be snap fitted or clamped together to form the magnetic stirrer, but one could consider an integrally molded part, obtained with a molding process by injection for example.

As for material, it is important to choose an inert material which will not react or pollute the sample to mix, and Polytetrafluoroethylene (PTFE) is a good example of material to use for such magnetic stirrer. As shown on figure 2, when the magnetic stirrer of figure 1 is placed in a vessel 100 to mix a liquid sample 200, the magnetic portion 10 is coupled to a magnetic motor placed in an apparatus 300 supporting the vessel 100.

The magnetic motor forces the magnetic stirrer to rotate around a vertical axis 310. The magnetic portion 10 with its height H1 mixes the liquid sample 200 in its vicinity, i.e. in a height H1 of the liquid sample 200 by creating turbulent conditions between the bars forming the cross.

The legs 31 and 32 are offset from the axis 310, so that their rotational movement around the axis 310 creates movements into the liquid sample 200, such as turbulent conditions. This allows an effective mixing of the liquid sample 200 along the height H2, even if the viscosity of the liquid sample is relatively important, like in a blood sample where the dynamic viscosity may be comprised between 4.10 ^"3 and 25.10 ^"3 Pa.s.

The elevated portion 20 is a beam of height H2, and again, the rotating movement of the magnetic stirrer is creating displacements in the liquid sample 200, to mix the liquid sample along the height H2.

Turning to figure 3, this figure represents a magnetic stirrer according to a second embodiment of the invention. The magnetic portion 10 is the same cross as the one of the first embodiment of figure 1 , as well as the elevated portion 20.

However, the connecting portion 30 is here in the form of a wall 33 with a flat cross section. To perform effective mixing along the height of the wall 33, two vertical lines of through holes 34 are implemented in the wall 33. The wall 33 presents a cross section with a height greater than its width, so that the rotational movement of the magnetic stirrer will create movements and displacements into the liquid sample to mix.

It is understood that obvious improvements and/or modifications for one skilled in the art maybe implemented and being under the scope of the invention as it is defined by the appended claims.