“Drill and fill” lithography for controlled fabrication of 3D platinum electrodes

Reproducible fabrication of three-dimensional (3D) metal electrodes is essential for accurate measurements of analyte in the fields of electroanalytical chemistry and biosensor development. Unfortunately, fabrication of these types of electrodes is complicated by the inherent complexity of current nano-fabrication methodologies. Herein, we report a simple and rapid fabrication method referred to as “drill and fill” lithography that provides control structuring and excellent reproducibility in the fabrication of 3D Pt electrodes with different sizes and shapes. The ability to combine “drill” and “fill” in a single technique using focused ion beam (FIB) lithography enabled precise control of the size and shape of the electrode depending on the amount of deposited metallic Pt. Electrodes were characterized using scanning electron microscopy, cyclic voltammetry, and Faradaic electrochemical impedance spectroscopy. The key innovation of this methodology lies in its simplicity and ability to tune the operating parameters to obtain electrodes of designated size and shapes. We envisage that these electrodes could be ideal for 'on-chip' diagnostic platforms.