Photosensitive-polyimide based method for fabricating various neural electrode architectures

Abstract

An extensive photosensitive-polyimide (PSPI)-based method for designing and fabricating various neural electrode architectures was developed. The method aims to broaden the design flexibility and expand the fabrication capability for neural electrodes to improve the quality of recorded signals and integrate other functions. After characterizing PSPI's properties for micromachining processes, we successfully designed and fabricated various neural electrodes even on a non-flat substrate using only one PSPI as an insulation material and without the time-consuming dry etching processes. The fabricated neural electrodes were an electrocorticogram (ECoG) electrode, a mesh intracortical electrode with a unique lattice-like mesh structure to fixate neural tissue, and a guide cannula electrode with recording microelectrodes placed on the curved surface of a guide cannula as a microdialysis probe. In vivo neural recordings using anesthetized rats demonstrated that these electrodes can be used to record neural activities repeatedly without any breakage and mechanical failures, which potentially promises stable recordings for long periods of time. These successes make us believe that this PSPI-based fabrication is a powerful method, permitting flexible design, and easy optimization of electrode architectures for a variety of electrophysiological experimental research with improved neural recording performance.

The Materials Science Foundation Supporting the Microfabrication of Reliable Polyimide–Metal Neuroelectronic Interfaces

“…Warnings of galvanic corrosion of such bimetallic junctions have been given, [ 1 ] but no significant corrosion related failure has been widely reported for polyimide–metal devices. Numerous examples of polyimide‐based neural devices exist that use TiPt, [ 66,67 ] TiAu, [ 68–70 ] CrAu, [ 71,72 ] etc. In addition, a multilayer stack of Pt/Au/Pt (i.e., platinum layers above and below a gold core) has been suggested to combine the improved stimulation and electrochemical behavior of platinum electrodes with the low resistance and power loss of mostly gold‐based traces.…”

${\mbi{\mu }}$-Foil Polymer Electrode Array for Intracortical Neural Recordings

“…The maximum thickness observed, using SEM, of the platinization layer was roughly \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(10~\mu \) \end{document} m, together with the thickness of the array the total thickness will be about \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(18~\mu \) \end{document} m at the tips. Other groups have developed flexible arrays with a similar thickness of 10- \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(25~\mu \) \end{document} m [2] , [8] , [10] , [22] – [24] , however, the size of the active sites on the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(\mu \) \end{document} -foil is considerably smaller, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(10~\mu \) \end{document} m \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(^{\mathrm {2}}\) \end{document} compared to 400- \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(8000~\mu \) \end{document} m \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(^{\mathrm {2}}\) \end{document} , in most prior art.…”

Materials and methods for the microfabrication of microfluidic biomedical devices

“…In a similar vein, PI has been used to make fl exible microfl uidic devices with embedded electronic circuits, such as neural electrodes (Kato et al ., 2012), microfl uidic mass spectrometers (Spectrometry et al ., 2010), bioelectric activity monitors , liquid fl ow sensors (Kuoni et al ., 2003), and impedance spectroscopy fl ow cytometers (Gawad et al ., 2001). …”