4 min read
Updated September 9, 2025
Site impedance sets part of the noise floor and caps how much charge a site can deliver. Z-Coat™ is a NeuroNexus site coating that lowers impedance by roughly an order of magnitude, and holds that value through repeated insertion.
Research use only. NeuroNexus products and the procedures described here are for non-clinical research use, and must not be used in human or veterinary medical procedures.
What it does#
Z-Coat™ increases the effective surface area of the site without changing its geometric area. The site occupies the same footprint on the shank, so spatial resolution is unchanged. The electrochemical interface behaves as though it were much larger.
Two things follow, and they are the reasons to specify it:
- For recording — lower impedance means less thermal noise from the interface and less attenuation into the amplifier input. Small-amplitude units that sat in the noise become separable.
- For stimulation — a larger effective area raises the charge a site can deliver inside safe limits. That matters most on small sites, where charge density is the binding constraint.
Why not a conventional conductive polymer#
Electrodeposited conductive polymers achieve comparable impedance reductions in the dish. The problem is what happens next: they delaminate under the mechanical stress of insertion, and their impedance drifts over a chronic implant. A coating that only works before the probe enters tissue does not help the experiment.
Z-Coat™ is mechanically stable through repeated insertion in vivo. That durability, not the impedance figure alone, is the design goal.
Optical stimulation#
Z-Coat™ reduces the photoelectric artifact that appears when a light pulse strikes a metal electrode site. In combined optogenetic and recording work the artifact occupies the same milliseconds as the response. Reducing it at the electrode is better than subtracting it afterwards.
Where it applies#
Coating support is a property of the probe design, not something added later, and Z-Coat™ is ordered as a per-channel service against the design you have selected — so it is priced by channel count and specified at order time, not fitted afterwards. Confirm that your design supports it before you order, with an application scientist rather than from a datasheet field.
Four situations make it worth specifying, and they are not the same argument:
| Specify Z-Coat when | The binding constraint | What the coating changes |
|---|---|---|
| Units are small, or the target fires sparsely | Interface thermal noise sits on top of the units you want | Lower impedance lowers the interface's noise contribution and its attenuation into the amplifier input, so small units separate from the floor |
| The protocol includes microstimulation on small sites | Charge density, not compliance voltage | A larger effective area raises the charge deliverable inside safe limits, at unchanged geometric area |
| The protocol combines optical stimulation with recording | The photoelectric artifact occupies the same milliseconds as the response | The artifact is reduced at the electrode, rather than subtracted in post |
| The probe will be used across many sessions | Impedance drift, not the initial value | The coating is mechanically stable through repeated insertion, so the baseline holds |
The common thread: in every row the geometric site area — and therefore the spatial resolution — is unchanged. Z-Coat buys electrochemical area, never footprint.
Handling#
Inspect before use. Examine the sites under magnification for coating uniformity, and measure impedance in saline. That value is the baseline every later measurement is compared against.
Insert normally. Z-Coat™ does not change the surgical technique. Standard sterile handling, standard insertion rate.
Measure before and after each session. A step change indicates mechanical damage; a slow rise across sessions is the normal ageing of the interface.
Clean by the standard protocol — enzyme before alcohol, never ultrasonic, never autoclave. See NeuroNexus Probe Usage Tips.
If impedance reads high#
- Confirm the measurement itself: connections, test frequency, and that saline covers the sites.
- Inspect for coating damage or residue under magnification.
- Compare against the site's own baseline rather than against a nominal figure.
Residue from incomplete cleaning is the most common cause, and it is reversible. Mechanical damage is not.
Support#
Technical questions: support@neuronexus.com · +1.734.913.8858