We employed two electrode formats, thin-film gold or gold disc electrodes, which we created using the following workflow. Disc electrodes were constructed by cutting 2 mm diameter gold working electrodes (CH Instruments, Austin, TX) to ~4 mm in thickness. After cutting, a working electrode wire was connected to the newly exposed gold surface with conductive, AgCl epoxy 8331D (MG Chemicals, British Columbia, Canada) and insulated with epoxy to passivate the exposed wire. We fabricated our thin-film gold electrodes as follows. Borosilicate glass was prepared for deposition by cleaning in piranha (5:1 H 2 SO 4 :H 2 O 2 ) followed by e-beam deposition of a 10 nM titanium layer for adhesion followed by a 100 nM gold layer. We patterned thin-film electrode via a wet etch process using AZ1518 positive photoresist with AZ400k developer (MicroChemicals, Ulm, Germany). Then we etched gold using aqua regia (3:1 HCl:HNO 3 ) followed by etching of titanium with a hydrofluoric acid (HF) solution (1:1:40 HF:H 2 O 2 :H 2 O). Residual photoresist was removed by rinsing with acetone. The CAD drawings for these custom electrodes are provided with the online supplemental material.