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This page describes products and general use; it is not medical advice.
Dry EEG electrodes (also written “dry electrode EEG”) record the brain’s electrical activity from the scalp without electrolyte gel. This page is for clinic staff, buyers and students who need to tell the dry designs apart, understand how they compare with gel-based electrodes, and know where the US regulatory line sits. Who uses them: anyone recording EEG from the scalp, in clinical and research settings, where setup time, comfort and signal quality all matter.
What dry EEG electrodes are
A dry EEG electrode is a scalp electrode that picks up the EEG signal without a conductive gel or paste between the electrode and the skin. It is a type of cutaneous electrode, which the FDA defines in 21 CFR 882.1320 as “an electrode that is applied directly to a patient’s skin either to record physiological signals (e.g., the electroencephalogram) or to apply electrical stimulation.” That regulation places cutaneous electrodes in Class II (performance standards).
The reference point for comparison is the wet (gel) electrode, which a 2014 review in Sensors calls the “gold standard” for EEG. The same review reports that dry electrode performance is “not far from those obtained with wet electrodes”, while noting that comparison studies lack a standard methodology.
How dry electrodes are built
With no gel to bridge the skin, a dry electrode must make contact another way: by pressing a conductive surface or probe against the scalp, by penetrating the outer skin layer (the stratum corneum), or by sensing the signal across a small air gap. Designs therefore differ mainly in their contact mechanism, covered in the next section. Fixation (the headset or cap that holds them in place) is part of the design: the review states that mechanical fixation “needs improvements in terms of comfort and discretion to consider it a wearable solution.”
Types of dry EEG electrodes
The table below summarises the families described in the Lopez-Gordo review (Sensors 2014; 14(7):12847-12870). Each row is taken from that paper; the impedance figures are as reported there, for the designs it describes, and are not a head-to-head test.
| Type | How it makes contact | Reported characteristic or limitation |
|---|---|---|
| Spiky (micro- or millimetre needles) | Needles of nano, micro or millimetre scale bypass the stratum corneum | Can be invasive, fragile and infection-prone; many designs untested on hair. Microneedle arrays reported as low as 0.65 kΩ at 1 kHz but up to 16 kΩ at 0.6 Hz; pyramidal microneedles about 13 kΩ once the stratum corneum is pierced; millineedles about 50 kΩ at DC-20 Hz |
| Capacitive (non-contact) | Sits about 3 mm above the scalp and senses the signal across the gap | Needs very high input impedance (about 1012 kΩ, or 1015 Ω, reported) and on-site amplification; low amplitude and motion artifacts from floating fixation |
| Foam | Conductive polymer foam with a fabric cover | Conforms to the irregular surface of the scalp |
| Spring-loaded | Multiple spring probes (for example a 17-probe design) reach the scalp through hair | Designed for contact through hair |
| Other: polymer bristles, quasi-dry, 3D-printed millineedles | Quasi-dry designs add a hydrating reservoir | Quasi-dry (sometimes called semi-dry) is therefore not strictly gel-free in the sense above |
Dry versus wet electrode impedance
Impedance is the opposition to current flow at the electrode-skin interface; lower values are generally easier to record through. The same review gives typical electrode-skin impedance as “150 to 200 KΩ and 5 to 10 KΩ before and after gel applications, respectively”, and reports that wet electrode impedance “deteriorated from 5 to 15 KΩ within 5 hours after gel application”, so gel is not stable over a long recording either.
For context, FDA’s recording-electrode guidance (below) cites the ANSI/AAMI EC12 benchmark for single-use gel electrodes: average AC impedance at 10 Hz of 2 kΩ at most across 12 pairs, and 3 kΩ at most for an individual pair. Those limits describe gel-type electrodes under that test; they are not a pass mark for dry designs.
How FDA treats cutaneous electrodes
Dry EEG electrodes fall under 21 CFR 882.1320 (product code GXY, Class II). FDA’s guidance “Cutaneous Electrodes for Recording Purposes – Performance Criteria for Safety and Performance Based Pathway” (issued August 14, 2020; nonbinding) sets an optional performance-criteria pathway for non-invasive, single-use recording electrodes used on normal, intact, clean skin with an electroconductive medium. Among the electrodes the guidance lists as not eligible for that pathway are “Dry electrodes (i.e., no electroconductive media is used)”, reusable electrodes, electrodes for stimulation and electrodes for use in an MR environment.
That exclusion is about the optional pathway only. It does not mean dry electrodes are unregulated or uncleared. The guidance also lists the skin-contact biocompatibility endpoints it expects for surface devices on intact skin: cytotoxicity, sensitization, and irritation or intracutaneous reactivity.
How to choose
Criteria below come from FDA guidance and the peer-reviewed review cited in Sources.
- Fit to the patient population and site. FDA’s guidance says electrode design (size, shape, type) should suit the site of application and intended use, and electrode size and spacing should suit the indicated population, for example children or adults.
- Single-use or reusable. The guidance’s pathway covers single-use electrodes; reusable and dry electrodes sit outside it.
- Contact through hair. The review notes that many spiky designs are untested on hair, while spring-loaded probes are designed to reach the scalp through hair.
- Amplifier compatibility. Capacitive designs need very high input impedance and on-site amplification, per the review.
For electrode families used elsewhere, see our guides on EMG electrodes and silver/silver chloride electrodes.
Safe use and handling basics
- FDA’s guidance covers electrodes applied only to normal, intact, clean, healthy skin; this applies to the surface-electrode class generally.
- Spiky designs penetrate the outer skin layer and the review describes them as potentially invasive and infection-prone, so follow the manufacturer’s instructions for use for any such product.
- Follow the manufacturer’s instructions for use for cleaning, reuse and storage; reusable status is a design property, not an assumption.
- Electrode placement over the scalp follows a position system such as the 10-20 system; see also EEG channels and EEG headbands.
Common mistakes
- Treating dry and quasi-dry as the same. Quasi-dry designs use a hydrating reservoir.
- Applying gel-electrode impedance limits to dry electrodes. The EC12 figures cited by FDA describe gel-type electrodes.
- Assuming “not eligible for the pathway” means “not allowed”. The exclusion applies to FDA’s optional performance-criteria pathway.
- Reading one paper’s impedance figure as a product specification. The review’s figures are per design and measurement condition, and it states comparisons lack standard methodology.
FAQ
Do dry EEG electrodes need gel?
No. By definition they record without electroconductive gel or paste. Quasi-dry designs are the exception in spirit: they use a hydrating reservoir. For the gel itself, see conductive gel.
Are dry EEG electrodes as good as wet ones?
The 2014 Sensors review calls wet electrodes the gold standard and reports dry performance “not far” from them, but says comparison methods are not standardised and more work is needed before dry electrodes could replace wet ones in clinical use.
What class is an EEG electrode?
A cutaneous electrode used to record EEG is Class II under 21 CFR 882.1320, product code GXY.
Why are dry electrodes excluded from FDA’s recording-electrode guidance pathway?
The guidance’s performance criteria assume an electroconductive medium and single use, and it lists dry electrodes among those not eligible for the pathway. It does not say why beyond that scope statement.
Sources
- eCFR, 21 CFR 882.1320 Cutaneous electrode, ecfr.gov (checked 2026-10-31).
- FDA, Cutaneous Electrodes for Recording Purposes – Performance Criteria for Safety and Performance Based Pathway, issued August 14, 2020, fda.gov (checked 2026-10-31).
- Lopez-Gordo MA, Sanchez-Morillo D, Pelayo Valle F. Dry EEG Electrodes. Sensors (Basel) 2014;14(7):12847-12870, PMC4168519 (checked 2026-10-31).
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