One limitation to the realisation of mass produced electrochemical cells is a lack of high resolution patterning techniques providing accurate alignment. A method of fabricating a patterned structure on a polymer layer for the manufacture of an electrochemical cell is provided. The method comprises: depositing a polymer layer upon a substrate; and stamping the polymer layer to form an embossed polymer layer using an embossing tool, the embossing tool having a first array of adjacent cells, spaced from one another and extending from the stamping face of the embossing tool and thereby forming a second array of adjacent cells, spaced from one another and extending as cavities within the embossed polymer layer.