Electroplating Optimization for BMEP Impedance

Once a BMEP syringe set is manufactured, electroplating of the BMEP recoding sites is required to lower impedance to suitable neural recording levels. Before electroplating, the impedance range of each channel is 2–4 MΩ with 9.6 μm wire and 2–3 MΩ with 12.7 μm wire. Using a custom in-house Matlab program and NanoZ (64 channels electroplating device, by Neuralynx), electroplating is automatically performed to lower the impedance of all individual electrodes of BMEP down to 200 kΩ for recording channels and 50 kΩ for the reference channel. Using a solution of gold solution and multi-walled carbon nanotubes, described previously (Kim et al., 2013 (link)), it was not possible to lower impedance to this 50 kΩ. However, using the platinum nanograss coating technique described in Boehler et al. (2015) (link) [2.5 mM Chloroplatinic acid (H₂PtCl₆) + 1.5 mM formic acid (HCOOH)], we can achieve impedance levels as low as 20 kΩ without any short circuit issues.