A 32-site neural recording probe fabricated by DRIE of SOI substrates

Abstract

An all-dry silicon-etch based micromachining process for neural probes was demonstrated in the manufacture of a probe with a 32-site recording electrode array. The fork-like probe shafts were formed by double-sided deep reactive ion etching (DRIE) of a silicon-on-insulator (SOI) substrate, with the buried SiO 2 layer acting as an etch stop. The shafts typically had the dimensions 5 mm × 25 µm × 20 µm and ended in chisel-shaped tips with lateral taper angles of 4 •. An array of Ir electrodes, each 100 µm 2 , and Au conductor traces were formed on top of the shafts by e-beam evaporation. An accompanying interconnect solution based on flexible printed circuitry was designed, enabling precise and flexible positioning of the probes in neural tissue. SEM studies showed sharply defined probes and probe tips. The electrical yield and function were verified in bench-top measurements in saline. The magnitude of the electrode impedance was in the 1 M range at 1 kHz, which is consistent with neurophysiological recordings.

State-of-the-art MEMS and microsystem tools for brain research

“…The planar lithography approach has evolved over the years to include integrated interconnects 38 , active electronics 35,39,40 , cochlear implants 41,42 , polytrodes 31 , and three-dimensional arrays 29,[43][44][45] . An important simplification for defining and releasing fine neural probe structures has been the use of silicon-on-insulator (SOI) wafers and deep reactive ion etching (DRIE) 46,47 that many groups have adopted.…”

Curvy surface conformal ultra-thin transfer printed Si optoelectronic penetrating microprobe arrays

“…Owing to its mechanical and electrical properties as well as the wellestablished manufacturing technologies, bulk silicon based probes have been extensively employed. 12,13,16 To accomplish the probe array, one typical approach involves first defining the electrical paths of the probes on a Silicon (Si) wafer and then isolating them into individual probes in plane, and finally, assembling them into a three-dimensional (3D) array with a rigid support. [13][14][15]17 The other approach is primarily based on micromachining the Si probes along the thickness direction of a Si wafer to form vertical arrays.…”

“…However, the arrays of the probes are mostly supported by rigid supports that interface with external signal extraction and processing units. 16,24,25 Recently, a flexible probe array was realized through fabricating metal electrodes on a relatively thick flexible polyimide substrate on a handling Si wafer, folding the probes from in-plane to out-of-plane to form an array, and removing the Si wafer by selective dry etching. 22 Such a device involved costly fabrication yet had limited functionality, i.e.…”

Microelectrode Arrays Modified with Nafion/Nanoporous AuPt Nanoparticles for in vivo Detection of Dopamine

“…The researchers could precisely define microelectrode parameters, such as electrode shape, size, and site position, by using MEMS technology and could fabricate multiple stimulation/recording sites on a single microelectrode shank. (1) The microelectrode arrays are a powerful tool for recording the electrical activity of nerve cells and helping researchers to further study information flow principles in the nervous system. In addition to recording electrophysiological signals, with the use of certain microelectrode materials, these microelectrode arrays could be used to detect neurotransmitter levels in the extracellular space by electrochemical techniques.…”