Figure 1

(a) Isometric view of two 3D electrodes showing the simulated 3D electrode geometry. The geometry of the green SU-8 insulation layer surrounding the gold 3D electrodes was approximated from the true appearance of a 3D electrode resulting from our fabrication process: a thick base that gradually turns into a uniform coating around the shaft due to the “wicking effect” from surface tension. Both electrodes have the same overall electrode height, SU-8 insulation height, and 3D electrode diameter, but different SU-8 insulation thicknesses. (b) Buckling simulation showing two 3D electrodes with different SU-8 thicknesses that are both subject to an identical, arbitrarily chosen, load at the tip. The body of the electrode with thicker SU-8 is deflected less. (c) Simulated electrode impedance at 1 kHz for different electrode diameters and insulation heights. Each curve represents the impedance of a 300 µm tall 3D electrode with various diameters of SU-8 insulation at a constant height. The trends in this plot indicate the correlation between uninsulated electrode surface area and the impedance of the electrode. As electrode diameter increases, impedance decreases due to a larger surface area. As the insulation height decreases, impedance decreases due to a larger uninsulated electrode surface area. (d) Simulated critical load factors for 300 µm tall 3D electrodes of different diameters, SU-8 thickness, and SU-8 height. Each plane represents a different gold electrode diameter. An increasing gold electrode diameter increases the load bearing capacity of the electrode structure. The load bearing capacity of a particular electrode diameter can be optimized by increasing the SU-8 height and thickness.