Plexon U-Probe

U-Probes* are Plexon’s most popular and fastest growing product in the electrodes, probes and arrays category.  They are exceptionally customizable and robust, multi-use, multi-site linear electrodes most often used for acute recordings in medium to large animals.

Flexibility in the manufacturing process allows for different electrode site arrangements and spacing, as well as optional fluid delivery channels for precise drug delivery or fiber optic lines for optogenetic stimulation intermixed within the recording sites. The precise linear arrangement of the electrode sites enables current source density analysis of the field potential signals as recorded from laminar neural structures.

The platinum/iridium electrode recording sites are available in 15, 20, 25 and 40µm diameter options. The small electrode site diameter (15µm) enables effective single-unit recording, while a unique etching process of the electrode surface results in lowered impedances without significantly changing the overall surface area of the exposed recording site. The result is a small site suitable for resolving single units coupled with low impedance for a better single-to-noise ratio.

U-Probes are conveniently available in single, stereotrode and tetrode configurations, each with a choice of 8, 16, 24, or 32 channels.

Below are all three 16 channel configurations illustrated with four fluid capillaries or optic fibers:

U-Probes are well known for their robustness due in part to their stainless steel construction (as opposed to silicon), and ability to penetrate deep within the brain. When used according to proper procedures, U-Probes will support many penetrations over a long period of time.

You may also wish to explore other options in Plexon’s family of specialty electrodes, probes and arrays including our V-Probes, Thumbtack Probe or the Floating Microelectrode Array (FMA), the latter two for chronic use.

U-Probes are Plexon’s most popular and fastest growing product in the electrodes, probes and arrays category. U-Probes are expertly handcrafted and made to order with many finished options available. As a result, please expect a six week manufacturing lead time for standard specifications. Some specifications or configurations, such as tetrodes, can take an additional two to three weeks. Your Plexon Sales Engineer is happy to provide additional information and to assist you in determining what might be the most advantageous U-Probe configuration.

The illustration below depicts the anatomy of a standard U-Probe by front and top (connector) view. The 8 channel, single electrode configuration is featured as the example (see page 8 of the U-Probe Technical Guide located in he Resources tab for more details on this particular channel count). Electrode sites are numbered from connector to tip.

The illustration below depicts the anatomy of a standard U-Probe by front and top (connector) view. The 8 channel, single electrode configuration is featured as the example (see page 8 of the U-Probe Technical Guide located in he Resources tab for more details on this particular channel count). Electrode sites are numbered from connector to tip.

U-Probes are customizable, as can be seen from the table below. It may also be possible to produce probes beyond the specifications below. As a result, it is recommended that you discuss your needs with a Plexon Sales Engineer to determine the best configuration and if your unique request can be accommodated.

Feature Specifications and Options Remarks
Application In vivo; acute
Channel counts 8, 16 24, or 32
Total probe length 30 to 150mm Length is customizable within range provided; however, the most typical request is 100mm. Total probe length is measured from tip to the connector. The difference between the total probe length and the reinforcement tube length is a minimum of 25mm.
Probe OD 185 to 360μm Probe diameters vary based on the number of electrodes, fluid channels and optic fibers. See the U-Probe diameter tables found in the U-Probe Technical Guide under Technical Specifications.
Reinforcement tube length 5 to 125mm Length is customizable within range provided
Reinforcement tube outer diameters 460 or 640μm Probe diameters of 236μm and greater require a 640μm reinforcement tube
Electrode construction 15μm Pt/Ir electrode site diameter, circuar shape, HML insulated (polyimide), and secured in medical-grade epoxy 15μm diameter sites are recommended for resolving single units (action potentials).
Electrode configurations Single, stereotrode or tetrode Single configuration is most typical; stereotrodes and tetrodes tend to be used in areas with an especially high density of neurons (i.e. hippocampus).
Inter-electrode spacing 50μm, 75μm, 100μm, 150μm, or 200μm along length of probe;
50μm within stereotrode or tetrode group
Distance from tip to the closest electrode site
Dependant on probe diameter (See table below):
185 probe diameter: 320μm; 210 probe diameter: 360μm; 236 probe diameter: 410μm
260 probe diameter: 450μm; 300 probe diameter: 520μm; 320 probe diameter: 560μm
360 probe diameter: 620μm
The numbering of the electrode sites is such that channel #1 is closest to the connector. Conversely, the electrode site closest to the tip is the largest channel # on the probe.
Stimulation options Single: Up to four fluid capillaries and/or optic fibers

Stereotrode or Tetrode: Up to two fluid capillaries and optic fibers

Single: Able to accomodate any combination of up to four additional fluid capillaries/optic fibers. Examples: four fluid capillaries; or four optic fibers; or one fluid capillary with three optic fibers. The total count of fluid capillaries plus optic fibers may not exceed four.

Stereotrode or Tetrode: Able to accomodate any combination of up to two additional fluid capillaries/optic fibers. The same examples that apply for the single configuration above apply here, however, the total count of fluid capillaries plus optic fibers may not exceed two.

Fluid capillary ID 40μm Fluid capillaries are slightly offset from the center line of the electrodes.
Fluid capillary OD 60μm
Optic fiber OD 50μm Optic fibers are slightly offset from the center line of the electrodes.
Connector interfaces
8 channel: CON/8o50m-10P
16 channel: 2x CON/8o50m-10P, CON/16m-V or CON/16o25m-18P
24 channel: 3x CON/8o50 or CON/32m-V
32 channel: CON/32m-V
All are Omnetics connectors.
Lifespan Robust and reusable with a minimum of thirty penetrations, likely many more

The two U-Probe diameter tables below provide the minimum diameters for all electrode, fluid capillary and optic fiber combinations.

Single Electrode Configuration:

Channels Fluid Capillaries or Optic Fibers Minimum Probe Diameter (μm)^ Minimum distance from tip to 1st electrode (μm) Reinforcement tube diameter (μm)^
8 0, 1 185 320 460 or 640
8 2 210 360 460 or 640
8 3 260 450 640
8 4 300 520 640
16 0 185 320 460 or 640
16 1 210 360 460 or 640
16 2 236 410 640
16 3 300 520 640
16 4 320 560 640
24 0 210 360 460 or 640
24 1 236 410 640
24 2
300
520 640
24 3 320 560 640
24 4 360 620 640
32 0 260 410 640
32 1 260 450 640
32 2 300 520 640
32 3 320 560 640
32 4 360 620 640

^Batch variation in wire inner diameter may require a larger probe diameter or larger reinforcement tube

Stereotrode/Tetrode Configurations:

Channels Fluid Capillaries or Optic Fibers Minimum Probe Diameter (μm)^ Minimum distance from tip to 1st electrode (μm) Reinforcement tube diameter (μm)^
8 0-1 185 320 460 or 640
8 2 210 360 460 or 640
16 0 185 320 460 or 640
16 1, 2 236 410 640
24 0 210 360 460 or 640
24 1,2 260 450 640
32 0 260 450 640
32 1,2 300 520 640

*U-Probes are manufactured by Neuronelektród.

^Batch variation in wire inner diameter may require a larger probe diameter or larger reinforcement tube.

Guides and How To Papers

Technical Specs and Data Sheets