Microelectrode

Résumé

A microelectrode is an electrode used in electrophysiology either for recording neural signals or for the electrical stimulation of nervous tissue (they were first developed by Ida Hyde in 1921). Pulled glass pipettes with tip diameters of 0.5 μm or less are usually filled with 3 molars potassium chloride solution as the electrical conductor. When the tip penetrates a cell membrane the lipids in the membrane seal onto the glass, providing an excellent electrical connection between the tip and the interior of the cell, which is apparent because the microelectrode becomes electrically negative compared to the extracellular solution. There are also microelectrodes made with insulated metal wires, made from inert metals with high Young modulus such as tungsten, stainless steel, or platinum-iridium alloy and coated with glass or polymer insulator with exposed conductive tips. These are mostly used for recording from the external side of the cell membrane. More recent advances in lit

Source officielle

https://en.wikipedia.org/wiki/Microelectrode

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PHOTOELECTRIC NEURAL INTERFACE COMBINING WIRE-BONDING mu LEDS WITH IRIDIUM OXIDE MICROELECTRODES FOR OPTOGENETICS

Xiang Chen

This paper reports the design, fabrication, electrical and thermal characterization, as well as attachment and stability of a flexible photoelectric neural interface (PENI). Upon the wire-bonding technology, three micro LED (mu LED) chips are well-connected to the polyimide substrate as an array, with their luminous surfaces over against the holes. Meanwhile, a Parylene-C-based array with four microelectrodes (200 mu m in diameter) modified by sputtering iridium oxide film is fabricated to record micro electrocorticography (mu ECoG) signals. Then, the back-to-back assembly is utilized to allow blue light through the aligned holes on both arrays with almost no attenuation. As an optogenetics tool, the PENI can be attached on the cortical surface of a mouse expressing ChR2 to realize synchronized light modulating and neural signal recording.

Ieee2017

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This paper describes the fabrication of polyimide-based microelectrodes with embedded fluidic microchannels. The thin-film structures combine for the first time a fluidic system with microelectrodes for recording and stimulation of biological signals on a flexible, implantable substrate. Microchannels were realized by a modified lamination technique and combined with a polyimide- platinum-polyimide sandwich structure. The probes can be used for monitoring cellular responses to various chemical stimuli delivered with high spatial precision.

2001

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Fabrication and test of implantable thin-film electrodes for stimulation and recording of biological signals

Daniel Bertrand, Raphael Holzer, Stefan Metz, Philippe Renaud

The fabrication, characterization and application of polyimide-based flexible microelectrodes for recording from and stimulation of biological tissue are described. The planar electrodes consist of a polyimide-platinum-polyimide sandwich structure with a total thickness of 10 to 40 mum fabricated on Pyrex or silicon wafers. Several designs with mono-polar or multi-polar probe-type electrodes have been realized. Two different fabrication technologies. photosensitive (PS-PI) and non-photosensitive polyimide (NPS- PI) have been developed. For the photostructurable polyimide 2 three-mask process was realized, whereas for the non-photosensitive polyimide a simpler two-mask process using dry etching techniques was used. A sacrificial layer of aluminum served for detachment of the structures by anodic metal dissolution. This is a particularly biocompatible release procedure as the microelectrodes are detached from the fabrication substrate in a sodium salt solution. Obtained microelectrodes were characterized by impedance spectroscopy and were used to record multi-channel EMG signals from free-walking insects.

2000

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