<p>What they are calling a &quot;pad&quot; might also be called a &quot;<a href="https://en.wikipedia.org/wiki/Electrical_contact" rel="nofollow noreferrer">contact</a>&quot;. The electrode is a <a href="https://en.wikipedia.org/wiki/Half-cell" rel="nofollow noreferrer">half-cell</a> that touches the nervous tissue/extracellular fluid; it's connected with a wire to the &quot;pad&quot;, which you'd then use some sort of connector to contact them and convey the signal to an amplifier. So the circuit is:</p>
<p>brain -&gt; electrode -&gt; pad -&gt; amplifier -&gt; ground (brain)</p>
<p>When they write</p>
<blockquote>
<p>metal lines interconnecting electrodes and I/O pads</p>
</blockquote>
<p>the &quot;metal lines&quot; are effectively wires, and by &quot;interconnecting&quot; they don't mean &quot;connecting both electrodes and I/O pads to (something)&quot; they mean &quot;connecting electrodes <em>to</em> I/O pads&quot;.</p>
<p>Here's another paper about the specific electrode design that I think is a bit more clear about their construction and the arrangement of the pads vs. electrodes:</p>
<p><a href="https://pubs.acs.org/doi/full/10.1021/acs.nanolett.7b03081" rel="nofollow noreferrer">Schuhmann Jr, T. G., Yao, J., Hong, G., Fu, T. M., &amp; Lieber, C. M. (2017). Syringe-injectable electronics with a plug-and-play input/output interface. Nano Letters, 17(9), 5836-5842.</a></p>
<p>In Figure 1a of that paper (see below), &quot;i&quot; is the electrode and &quot;iii&quot; are the pads, ready for a connector.</p>
<p><a href="https://i.sstatic.net/kcNJS.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/kcNJS.png" alt="Electrodes and pads" /></a></p>
<p>You might find things described as &quot;pads&quot; elsewhere that are really just the electrodes themselves encased in something soft-and-sticky; for example, the electrodes in an EKG or rudimentary EEG look something like this:</p>
<p><a href="https://i.sstatic.net/1TTDv.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/1TTDv.png" alt="EKG pad" /></a></p>
<p>These hold the electrodes themselves against the skin, usually with a conductive gel placed underneath for better contact, but there's really no relationship to the pads in the paper you linked.</p>

CC BY-SA 4.0
2023-01-20T20:52:15.977Z
2023-01-20T20:58:58.473Z
2023-01-20T20:58:58.473Z
Bryan Krause
<p>Some authors seem to use these terms interchangeably, others distinctly.</p>
<p>What is a pad? How is it different from an electrode? Is a pad where stimulation can happen? Can recording also happen at a pad? What is the material/electronic difference?</p>
<p>Here's an example of a sentence that I find difficult to interpret:</p>
<p>&quot;The freestanding polymer–metal–polymer structure of mesh
electronics has exposed recording electrodes and I/O
pads, whereas all metal lines interconnecting electrodes
and I/O pads are encapsulated by the two polymer layers.&quot;</p>
<p><a href="https://www.nature.com/articles/s41583-019-0140-6" rel="nofollow noreferrer">https://www.nature.com/articles/s41583-019-0140-6</a></p>

<neurophysiology><electrophysiology>
What is the difference between "electrode" and "pad" on extracellular probes?
user90664
# What is the difference between "electrode" and "pad" on extracellular probes?

(Asked by: username_0 on 2023-01-20)

Some authors seem to use these terms interchangeably, others distinctly.

What is a pad? How is it different from an electrode? Is a pad where stimulation can happen? Can recording also happen at a pad? What is the material/electronic difference?

Here's an example of a sentence that I find difficult to interpret:

"The freestanding polymer–metal–polymer structure of mesh
electronics has exposed recording electrodes and I/O
pads, whereas all metal lines interconnecting electrodes
and I/O pads are encapsulated by the two polymer layers."

<https://www.nature.com/articles/s41583-019-0140-6>

**Tags:** neurophysiology, electrophysiology


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## 1 answers

### Answer by username_1 on 2023-01-20. Score: 1 | Accepted answer

What they are calling a "pad" might also be called a "[contact](https://en.wikipedia.org/wiki/Electrical_contact)". The electrode is a [half-cell](https://en.wikipedia.org/wiki/Half-cell) that touches the nervous tissue/extracellular fluid; it's connected with a wire to the "pad", which you'd then use some sort of connector to contact them and convey the signal to an amplifier. So the circuit is:

brain -> electrode -> pad -> amplifier -> ground (brain)

When they write

> metal lines interconnecting electrodes and I/O pads

the "metal lines" are effectively wires, and by "interconnecting" they don't mean "connecting both electrodes and I/O pads to (something)" they mean "connecting electrodes *to* I/O pads".

Here's another paper about the specific electrode design that I think is a bit more clear about their construction and the arrangement of the pads vs. electrodes:

[Schuhmann Jr, T. G., Yao, J., Hong, G., Fu, T. M., & Lieber, C. M. (2017). Syringe-injectable electronics with a plug-and-play input/output interface. Nano Letters, 17(9), 5836-5842.](https://pubs.acs.org/doi/full/10.1021/acs.nanolett.7b03081)

In Figure 1a of that paper (see below), "i" is the electrode and "iii" are the pads, ready for a connector.

[![Electrodes and pads](https://i.sstatic.net/kcNJS.png)](https://i.sstatic.net/kcNJS.png)

You might find things described as "pads" elsewhere that are really just the electrodes themselves encased in something soft-and-sticky; for example, the electrodes in an EKG or rudimentary EEG look something like this:

[![EKG pad](https://i.sstatic.net/1TTDv.png)](https://i.sstatic.net/1TTDv.png)

These hold the electrodes themselves against the skin, usually with a conductive gel placed underneath for better contact, but there's really no relationship to the pads in the paper you linked.


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