A microfluidic device comprising: a substrate having a microfluidic flow channel; a first and a second electrode channel (20A, 20B), wherein the first electrode channel is arranged on one side of the microfluidic flow channel and extends transverse of the microfluidic flow channel and terminates a distance Δ from the adjacent rim or edge of the microfluidic flow channel and the second electrode channel is arranged on the other side of the microfluidic flow channel and also terminates a distance Δ from its adjacent rim or edge of the microfluidic flow channel, the electrode channel (20A, 20B) having an electrically conductive ink layer arranged on a primer layer which is in the first and second electrode channel (20A, 20B) in the substrate, and wherein a. the primer layer comprises: (i) an organic polymer selected from the group consisting of: (a) a homopolymer or copolymer including a vinyl lactam repeating unit; (b) a cellulose ether; (c) polyvinyl alcohol; and (d) unmodified or modified gelatin; (ii) a porous particulate material, the organic polymer being dispersed in the porous particulate material; b. the electrically conductive ink layer comprises electrically conductive particles dispersed in a humectant organic solvent. a substrate having a microfluidic flow channel; a first and a second electrode channel (20A, 20B), wherein the first electrode channel is arranged on one side of the microfluidic flow channel and extends transverse of the microfluidic flow channel and terminates a distance Δ from the adjacent rim or edge of the microfluidic flow channel and the second electrode channel is arranged on the other side of the microfluidic flow channel and also terminates a distance Δ from its adjacent rim or edge of the microfluidic flow channel, the electrode channel (20A, 20B) having an electrically conductive ink layer arranged on a primer layer which is in the first and second electrode channel (20A, 20B) in the substrate, and wherein a. the primer layer comprises: (i) an organic polymer selected from the group consisting of: (a) a homopolymer or copolymer including a vinyl lactam repeating unit; (b) a cellulose ether; (c) polyvinyl alcohol; and (d) unmodified or modified gelatin; (ii) a porous particulate material, the organic polymer being dispersed in the porous particulate material; b. the electrically conductive ink layer comprises electrically conductive particles dispersed in a humectant organic solvent. a. the primer layer comprises: (i) an organic polymer selected from the group consisting of: (a) a homopolymer or copolymer including a vinyl lactam repeating unit; (b) a cellulose ether; (c) polyvinyl alcohol; and (d) unmodified or modified gelatin; (ii) a porous particulate material, the organic polymer being dispersed in the porous particulate material; (i) an organic polymer selected from the group consisting of: (a) a homopolymer or copolymer including a vinyl lactam repeating unit; (b) a cellulose ether; (c) polyvinyl alcohol; and (d) unmodified or modified gelatin; (a) a homopolymer or copolymer including a vinyl lactam repeating unit; (b) a cellulose ether; (c) polyvinyl alcohol; and (d) unmodified or modified gelatin; (ii) a porous particulate material, the organic polymer being dispersed in the porous particulate material; b. the electrically conductive ink layer comprises electrically conductive particles dispersed in a humectant organic solvent.