Microfluidic devices and methods of manufacture thereof

1. A microfluidic device, comprising:

a substrate comprising a microfluidic channel; and

an electrically conductive feature comprising an electrically conductive layer arranged on a primer layer and positioned with reference to the microfluidic channel, wherein the primer layer comprises:

(i) an organic polymer selected from the group consisting of

(a) a homopolymer or copolymer comprising a vinyl lactam repeating unit,

(b) a cellulose ether,

(c) polyvinyl alcohol, and

(d) unmodified or modified gelatin, and

(ii) a porous particulate material,

wherein the porous particulate material is dispersed in the organic polymer, and

wherein the microfluidic channel comprises a side wall portion that joins an upper surface of the substrate at a rim and a lateral separation δ exists between the rim of the microfluidic channel and the edge of the electrically conductive layer.

2. The microfluidic device of claim 1 , wherein the primer layer comprises at least 70% by weight of the porous particulate material, based on a total weight of the organic polymer and porous particulate material.

3. The microfluidic device of claim 2 , wherein the primer layer comprises up to 30% by weight of the organic polymer, based on a total weight of the organic polymer and porous particulate material.

4. The microfluidic device of claim 1 , wherein the primer layer comprises at least 90% by weight of the porous particulate material, based on a total weight of the organic polymer and porous particulate material.

5. The microfluidic device of claim 4 , wherein the primer layer comprises up to 10% by weight of the organic polymer, based on a total weight of the organic polymer and porous particulate material.

6. A method of manufacturing a microfluidic device, the method comprising:

(A) applying a primer layer to a substrate comprising a microfluidic channel, the primer layer comprising:

(i) an organic polymer selected from the group consisting of

(a) a homopolymer or copolymer comprising a vinyl lactam repeating unit,

(b) a cellulose ether,

(c) polyvinyl alcohol, and

(d) unmodified or modified gelatin, and

(ii) a porous particulate material, wherein the porous particulate material is dispersed in the organic polymer;

(B) applying a conductive ink layer over the primer layer at a position referenced to the microfluidic channel, the conductive ink comprising electrically conductive particles dispersed in a humectant organic solvent,

wherein during (A) applying the primer layer and/or (B) applying the conductive ink layer, the primer layer and/or the conductive ink layer are applied to the microfluidic channel, and

wherein the microfluidic channel comprises a side wall portion that joins an upper surface of the substrate at a rim and the conductive ink layer is applied in the microfluidic channel so that a lateral separation δ exists between the rim of the conductive ink channel and the edge of the conductive ink layer.

7. The method according to claim 6 , wherein, during (A) applying the primer layer and/or (B) applying the conductive ink layer, the primer layer and/or the conductive ink layer are applied in solution to the microfluidic channel and are distributed through the microfluidic channel by capillary action.

8. The method according to claim 6 , wherein the organic polymer is a homopolymer or copolymer of vinyl pyrrolidone.

9. The method according to claim 8 , wherein the organic polymer is a copolymer of vinyl pyrrolidone and dimethylaminoethylmethacrylate.

10. The method according to claim 6 , wherein the porous particulate material is selected from the group consisting of silica, alumina, titania, a zeolite, and barium sulphate.

11. The method according to claim 6 , wherein the primer layer is applied to the substrate diluted in a hydrophilic solvent.

12. The method according to claim 11 , wherein the hydrophilic solvent is a glycol ether or a mixture thereof.

13. The method according to claim 6 , wherein the electrically conductive particles in the conductive ink comprise a metal selected from the group consisting of nickel, copper, palladium, silver, platinum and gold, or any mixture thereof.

14. The method according to claim 6 , wherein the humectant organic solvent in the conductive ink is a polyol.

15. A microfluidic device manufactured according to the method of claim 6 .