Fabrication and Characterization of 3D Micro- and Nanoelectrodes for Neuron Recordings

Abstract

In this paper we discuss the fabrication and characterization of three dimensional (3D) micro- and nanoelectrodes with the goal of using them for extra- and intracellular studies. Two different types of electrodes will be described: high aspect ratio microelectrodes for studying the communication between cells and ultimately for brain slice recordings and small nanoelectrodes for highly localized measurements and ultimately for intracellular studies. Electrical and electrochemical characterization of these electrodes as well as the results of PC12 cell differentiation on chip will be presented and discussed.

Novel 3D microelectrodes and pipettes by wet and dry etching

“…The fabrication process for the small electrodes is similar to that presented in [14] but with two essential changes. First, by utilising a high resistivity wafer (10,000 X cm instead of the previously used 1-20 X cm) we avoid having to isolate the resulting pillars by a thick oxide layer.…”

“…We have previously presented a fabrication process for 3D micro-and nanoelectrodes [14]. In the case of the small electrodes, the KOH wet etch based process resulted in very sharp structures, however, after isolation (by silicon oxide deposition) and metal deposition, the tip size was extended to dimensions around 500 nm-1 lm, which is too big for cell penetration.…”

“…The realization that 3D electrodes present higher signal-tonoise ratios due to their increased surface area [9,14] and ability to reach neurons inside the dead cell layer surrounding tissue slices, led to an increased interest for fabricating novel 3D structures on several materials and with a variety of fabrication techniques, though most work has been done on high aspect ratio electrodes and reports of fabrication of smaller 3D electrodes are limited.…”

Beam induced deposition of 3D electrodes to improve coupling to cells

“…Several studies have also suggested the use of sharp protruding electrodes (sharp micromachined tips, Si nanowires) to penetrate the membrane of cultured cells, thus directly recording the intracellular potential modulation [3,4]. Nevertheless, penetration into cytoplasm may result harmful for the cell itself, causing alteration in electrical behavior or its death.…”

“…Three-dimensional structuring of metallic electrodes has been proposed as a strategy to improve in vitro recording from brain slices [2,3]. Several studies have also suggested the use of sharp protruding electrodes (sharp micromachined tips, Si nanowires) to penetrate the membrane of cultured cells, thus directly recording the intracellular potential modulation [3,4].…”