Written and maintained by CASRAI Editorial Board
Last updated
A multi-electrode array (MEA) is a device with many small electrodes that records the electrical activity of many cells at once and, in many designs, can also stimulate them. The same device is called a microelectrode array or multielectrode array; the terms are used interchangeably. This page is for lab staff and students who need to tell the main MEA formats apart and understand what the numbers on a datasheet mean.
Who uses it: neuroscience and cardiac research labs working with cultured neurons, acute tissue slices, retina and cultured cardiomyocytes. It is a research instrument, not a clinical device.
What is a multi-electrode array (MEA)?
Obien et al. (2015) describe the term as covering substrate-integrated planar MEAs and implantable neural probes. These devices record extracellular signals, meaning local field potentials and action potentials, from many neurons simultaneously on a millisecond timescale, and they can also deliver stimulation (Frontiers in Neuroscience, checked 2026-11-07).
Compared with a single macroelectrode, the Forschungszentrum Julich institute lists these advantages for microelectrode arrays: better signal-to-noise ratio, high mass transfer, spatial resolution and redundant signals (checked 2026-11-07).
How an MEA works and is built
Each electrode is a small conductive site on a substrate. A dielectric passivation layer covers the wiring, with openings that define the active electrode area. In the Julich silicon chip, for example, a 24 x 24 mm chip carries a 1.4 x 1.4 mm sensor area with 64 gold microelectrodes in an 8 x 8 grid, and the passivation openings set electrode diameters between 3 and 24 micrometres.
Electrodes pick up voltage changes in the fluid next to the cells and pass them to an amplifier. Obien et al. distinguish two architectures:
- Passive MEAs contain no circuit elements such as transistors. Fixed wiring runs to external amplifiers, and passive MEAs have been commercially available since the late 1990s.
- Active (CMOS) MEAs integrate electronics with the electrodes, which allows a much higher electrode number and density.
Types of MEA
| Type | Typical use | Key difference (sourced) |
|---|---|---|
| Passive planar MEA | In vitro recording from cultures and tissue | No on-chip circuitry; fixed wiring to external amplifiers; parasitic capacitance can be significantly larger than in CMOS devices; one study cited by Obien et al. measured 60-100 pF |
| Active CMOS high-density MEA | High-resolution in vitro recording and stimulation | Electronics integrated with electrodes; parasitic capacitance estimated below 0.5 pF in one high-density device; an 11,011-electrode MEA and a stimulation device near 7000 electrodes/mm2 are reported (Obien et al. 2015) |
| Implantable neural probe | Recording in tissue in vivo | Included within the MEA term by Obien et al. 2015, alongside planar devices |
| Flexible polymer-substrate MEA (flexMEA) | Recording on a flexible substrate | Polymer substrate instead of silicon (Julich) |
| Interdigitated electrodes (IDEs) | Impedance and capacitance biosensing | Comb-shaped electrode layout (Julich) |
Electrode sizes, materials and speed
Obien et al. report that published microelectrodes range from 5 to 50 micrometres in diameter. CMOS devices read out at frame rates of about 2-10 kHz, with some reaching 77 kHz.
| Item | Examples named in the source |
|---|---|
| Electrode conductors | Gold, titanium nitride, platinum, stainless steel, aluminium, iridium oxide |
| Coatings that lower impedance | Platinum black, gold nanostructures, carbon nanotubes, PEDOT |
| Emerging materials | Doped diamond, graphene |
Impedance-lowering modifiers are used because electrode impedance affects how well the small extracellular signal reaches the amplifier. Impedance is also a key specification for other electrode devices; see dry EEG electrodes for a different, EEG-based example.
What MEAs record and which preparations
MEAs record extracellular local field potentials and action potentials. Obien et al. list in vitro uses including acute retina (mouse, rat, rabbit, guinea pig, human), cultured neurons, acute slices (cerebellum, cortex, olfactory bulb) and cultured cardiomyocytes. Optical methods such as calcium imaging measure a different signal and are often used alongside electrical recording. The Julich group also describes aptamer-modified electrodes for detecting analytes and neurotransmitters.
Choosing a format
- Electrode number and density: active CMOS devices offer much higher numbers and density than passive MEAs (Obien et al.).
- Recording only, or recording with stimulation: MEAs can do both, but this depends on the device (Obien et al.).
- Chip or plate format: specifications differ between products, so confirm the exact product with the manufacturer.
- Electrode size against the target: published electrodes span 5 to 50 micrometres (Obien et al.).
Common mistakes
- Treating “MEA” as one specification. Passive and CMOS devices differ in capacitance, electrode count and readout speed.
- Comparing electrode counts without electrode density or diameter.
- Assuming a device that records can also stimulate. Check the specification of the whole system.
FAQ
Is a microelectrode array the same as a multielectrode array?
In practice yes. Obien et al. use “microelectrode array” for the class that includes planar MEAs and implantable probes, and “multi-electrode” and “multielectrode” are used for the same devices.
What does an MEA record?
Extracellular local field potentials and action potentials from many cells at once, at millisecond resolution.
What is the difference between passive and active MEAs?
Active MEAs contain circuit elements such as transistors next to the electrodes; passive MEAs do not and rely on external amplifiers.
For related topics, see what is biophysics and TIRF microscopy.
Sources
- Obien MEJ et al. (2015). Revealing neuronal function through microelectrode array recordings. Frontiers in Neuroscience. https://www.frontiersin.org/articles/10.3389/fnins.2014.00423/full. Checked 2026-11-07.
- Forschungszentrum Julich, Microelectrode arrays. https://www.fz-juelich.de/en/ibi/ibi-3/research/microelectrode-arrays. Checked 2026-11-07.
