The invention disclosed herein relates to a biological fluid constituent sampling and concentration measurement device, said device comprising: an array of micro-needles, each micro-needle having an access opening a layer of hyrdophilic gel material over the array a first layer of conductive material over the layer of hydrophilic gel material, wherein the first layer of conductive material is porous and further wherein the access openings, the layer of hydrophilic gel material and the first layer of conductive material provide a constituent transfer pathway and a second layer of conductive material, wherein the first layer of conductive material and the second layer of conductive material are spaced-apart, wherein biological fluid present at the access opening is caused to be transferred to the space between the first and second layers of conductive material.
