An electrode structure has a layer of at least two interdigitated materials, a first material being an electrically conductive material and a second material being an ionically conductive material, the materials residing co-planarly on a membrane in fluid form, at least one of the interdigitated materials forming a feature having an aspect ratio greater than one. A method of forming an electrode structure includes merging flows of an electrically conductive material and a second material in a first direction into a first combined flow, dividing the first combined flow in a second direction to produce at least two separate flows, each separate flow including flows of the electrically conductive material and the second material, merging the two separate flows into a second combined flow, repeating the merging and dividing flow as desired to produce a final combined flow, and depositing the final combined flow as an interdigitated structure in fluid form onto a substrate such that at least one of the materials forms a feature in the structure having an aspect ratio greater than one.