Multichannel Systems MEA Manual - Manual (Page 10)

MEA Manual
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3.2 MEA Design and Production
A standard MEA biosensor has a square recording area of 700 μm to 5 mm length. In this area,
60 electrodes are aligned in an 8 x 8 grid with interelectrode distances of 100, 200, or 500 μm. Planar
TiN (titanium nitride) electrodes are available in sizes of 10, 20, and 30 μm, and three-dimensional TiN
electrodes have a diameter of > 20 μm at the base with a very fine tip. Standard MEAs are useful for
a wide variety of applications. Different geometries match the anatomical properties of the preparation.
Most MEAs are available with a substrate-integrated reference electrode replacing the silver pellet in the
bath. All electrodes can either be used for recording or for stimulation.
In principle MEA electrodes are not arranged symmetrical, so the MEA chip has to be placed inside the
amplifier in the recommended manner.
Several other MEA types and layouts that are dedicated to special applications are also available, please
see chapter “MEA Types and Layouts” for more details.
The biological sample can be positioned directly on the recording area; the MEA serves as a culture and
perfusion chamber. A temperature controller controls the temperature in the culture chamber. Various
culture chambers are available, for example, with leak proof lid or with semipermeable seal. An incubator
is not necessarily required, long-term recordings in the MEA culture chamber are possible over several
weeks or even months.
For cell or slice cultures, MEAs have to be coated with standard procedures before use to improve the cell
attachment and growth, please read chapter “MEA Coating”.
Spike activity can be detected at distances of up to 100 μm from a neuron in an acute brain slice. Typically,
signal sources are within a radius of 30 μm around the electrode center. The smaller the distance, the
higher are the extracellular signals. The higher the spatial resolution, the lower the numbers of units that
are picked up by a single electrode, that is, the less effort has to be put into the spike sorting.
Multi Channel Systems provides MEAs with the highest spatial resolution in the market. HighDenseMEAs
have electrodes with a diameter of only 10 μm arranged in a distance of only 30 μm (center to center).
The challenge of manufacturing very small electrodes and at the same time keeping the impedance and
the noise level down has been met by introducing a new electrode material: Titanium nitride (TiN).
The NMI in Reutlingen, Germany (www.nmi.de), produces MEAs from very pure fine quality and highly
biocompatible materials. The NMI is a research institute, with which Multi Channel Systems has
collaborated in many projects and over many years.
Quality controls and production processes have been improved over the last years so that MEAs are always
of a fine consistent quality at very reasonable prices.