Apparatus and methods for controlled electrochemical surface modification

A method of focusing charge density at a functional surface on an electrode array and electrochemically modifying an active species in a conductive solution exposed to the electrode array, the method comprising the steps of:

• a. providing an electrode array, wherein:
• i. the electrode array comprises a support substrate;
• ii. the electrode array comprises a plurality of surface structures protruding from an upper surface of the support substrate, wherein the plurality of surface structures include an electrode layer;
• and
• iii. the plurality of surface structures have a plurality of functional surfaces, each of the plurality of surface structures having a functional surface on the electrode layer, wherein each functional surface is on an upper portion of a surface structure of the plurality of surface structures, wherein each functional surface is adapted to contact an active species in a conductive solution, and wherein the plurality of functional surfaces are electrically connected via the electrode layer to form a functional grouping;
• b. exposing the plurality of surface structures to the conductive solution comprising an active species, in which a counter electrode is positioned;
• and
• c. establishing a current or voltage between the plurality of functional surfaces on the electrode layer and the counter electrode such that the charge density is focussed at the plurality of functional surfaces on the electrode layer and the active species is electrochemically modified following contact with the plurality of functional surfaces;
• wherein the active species comprises a species and wherein the species is selectively attached to the plurality of functional surfaces following the electrochemical modification, the size of each functional surface being variable depending upon the focussed charge density, and each functional surface being a region where attachment occurs at a faster kinetic rate when compared to another surface on the electrode array at which charge density is not focused;
• and
• wherein the electrode array comprises a first binding layer covering the functional surface and at least part of the plurality of surface structures and the support substrate of the electrode array, wherein the step of establishing the current or voltage between the electrode layer and the counter electrode results in selective removal of the first binding layer from the functional surface compared to the plurality of surface structures and the support substrate of the electrode array.