Ultrasonic welding of a microfluidic device

1. An ultrasonic welding-based device provided with a microfluidic path for a fluid, the device being mainly made of a first element and a second element welded one to the other via at least one structure, said structure comprising:

an elongated welded portion providing said welding, resulting from the melting of an initial energy director when using ultrasound welding,

a welding channel extending between the first and second elements and along one side of the welded portion, and

a draining channel communicating with the welding channel and said microfluidic path.

2. Ultrasonic welding-based device of claim 1 , wherein said structure comprising a second welding channel extending between the first and second elements and along the opposite side of the elongated welded portion.

3. Ultrasonic welding-based device of claim 2 , wherein said draining channel further communicates with said second welding channel.

4. Ultrasonic welding-based device of claim 2 , wherein said structure further comprises a second draining channel communicating with said second welding channel and said microfluidic path.

5. Ultrasonic welding-based device of claim 4 , wherein said second draining channel further communicates with said welding channel.

6. Ultrasonic welding-based device of claim 5 , wherein said draining channel further communicates with said second welding channel.

7. Ultrasonic welding-based device of claim 1 , comprising an array of welded junctions adjacent to each other and separated one to the other by respective walls, each one of said welded junctions in the array comprising a welded portion providing a welding and resulting from the melting of an initial energy director when using ultrasound welding, wherein the array comprises at least one of said structure.

8. Ultrasonic welding-based device of claim 7 , wherein the array of welded junctions comprising at least two of said structures having the same draining channel(s).

9. Ultrasonic welding-based device of claim 7 , wherein the height of the wall(s) determine(s) the height of the welding channels.

10. Ultrasonic welding-based device of claim 1 , wherein this device is arranged such that, when the device is in use, the fluid flows mainly in the microfluidic path into a determined flowing direction in proximity with the connection with said at least one draining channel, and wherein this at least one draining channel extends mostly perpendicular to this flowing direction.

11. Ultrasonic welding-based device of claim 1 , further arranged in such a way that the fluid resistance in the draining channel is higher than in the microfluidic path, at the location where the draining channel communicates with the microfluidic path such that a fluid filled in the microfluidic path goes preferentially to the microfluidic path at this location.

12. Ultrasonic welding-based device of claim 1 , wherein at least one structure comprises surfaces having hydrophobic, oleophobic or omniphobic property.

13. Ultrasonic welding-based device of claim 1 , wherein at least one structure comprises surfaces provided with nano-scale or micro-scale structure elements enhancing the hydrophobic, oleophobic or omniphobic property of these surfaces.

14. Ultrasonic welding-based device of claim 13 , wherein the first element is a foil or a laminate.

15. A method of manufacturing a microfluidic device from a first element and a second element to be welded one to the other, comprising:

(a) forming said first element;

(b) forming said second element;

(c) assembling the first and the second elements; and

(d) ultrasonically welding the first with the second elements;

wherein step (a) and/or (b) comprises the forming on a main face of the first and/or second elements (respectively) of at least one elongated energy director;

wherein step (a) comprises the forming, on a main face of the first element of:

microfluidic cavities to provide at least a part of a microfluidic path for a fluid once the first and second elements are welded one to the other; and of

at least one welding groove, and a draining channel or groove communicating with at least one welding groove, such that:

corresponding welding channel(s) extend(s) between the first and second elements, that

said at least one welding groove further extends along one side of the energy director, and that

the draining channel or groove communicates with some microfluidic cavities,

once the first and second elements are assembled in step (c); and

wherein step (d) comprises applying an ultrasonic energy to the energy director(s) to perform the welding at the energy director(s).

16. Method of claim 15 , further comprising, between steps (a) and (c), provision of a liquid on the first element, such that the liquid is present into the microfluidic path before the first and second elements are welded one to the other, and optionally a further step of drying this liquid is implemented before or after step (d).

17. A base part to be ultrasonically welded to a top part for making a device provided with integrated microfluidic path of a fluid, said base part comprising cavities for the microfluidic path and a structure comprising:

an elongated energy director arranged to be partly melted when applying appropriate ultrasound energy for said welding purpose,

a welding groove extending along one side of the energy director, and

a draining groove communicating with the welding groove and said microfluidic cavities.