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Photosensitive-polyimide based method for fabricating various neural electrode architectures.

Kato YX, Furukawa S, Samejima K, Hironaka N, Kashino M - Front Neuroeng (2012)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Brain Science Institute, Tamagawa University, Machida Tokyo, Japan.

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.

No MeSH data available.


Schematic diagram of the manufacturing process for the ECoG electrode with MEMS surface-micromachining technologies. Column (A): Conventional fabrication method for non-photosensitive material (non-PSM). Column (B): Fabrication method in this study for photosensitive material (PSM). Dry etching process is green color area from (A-5) to (A-9). (A-1) Cr is deposited on glass on substrate. (A-2) Non-PSM is deposited. (A-3) Chromium/gold is deposited and the recording microelectrodes and hard wiring are patterned. (A-4) Non-PSM is deposited again. (A-5) Aluminum is deposited as a mask for plasma etching. (A-6) Aluminum mask is patterned for the outer geometry and the through-holes of the ECoG electrode. (A-7) Non-PSM is patterned to define the outer geometry and the through-holes of the ECoG electrode by plasma etching. (A-8) Aluminum mask is patterned for the outer geometry, the exposed recording microelectrode sites, and the through-holes by plasma etching. (A-9) Non-PSM is patterned to expose the outer geometry, the exposed recording microelectrode sites, and the through-holes by plasma etching. (A-10) Aluminum is removed. (A-11) The ECoG electrode is lifted off. (B-1) Cr is deposited on glass on substrate. (B-2) PSM is deposited on substrate. (B-3) PSM is patterned to define the outer geometry and the through-holes of the ECoG electrode. (B-4) Chromium/gold is deposited and the recording microelectrodes and hard wiring are patterned. (B-5) PSM is deposited again. (B-6) The outer geometry, the exposed recording microelectrode sites, and the through-holes of the ECoG electrode are patterned. (B-7) The ECoG electrode is lifted off. Large box at the bottom is a magnified illustration of a through-hole.
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Figure 1: Schematic diagram of the manufacturing process for the ECoG electrode with MEMS surface-micromachining technologies. Column (A): Conventional fabrication method for non-photosensitive material (non-PSM). Column (B): Fabrication method in this study for photosensitive material (PSM). Dry etching process is green color area from (A-5) to (A-9). (A-1) Cr is deposited on glass on substrate. (A-2) Non-PSM is deposited. (A-3) Chromium/gold is deposited and the recording microelectrodes and hard wiring are patterned. (A-4) Non-PSM is deposited again. (A-5) Aluminum is deposited as a mask for plasma etching. (A-6) Aluminum mask is patterned for the outer geometry and the through-holes of the ECoG electrode. (A-7) Non-PSM is patterned to define the outer geometry and the through-holes of the ECoG electrode by plasma etching. (A-8) Aluminum mask is patterned for the outer geometry, the exposed recording microelectrode sites, and the through-holes by plasma etching. (A-9) Non-PSM is patterned to expose the outer geometry, the exposed recording microelectrode sites, and the through-holes by plasma etching. (A-10) Aluminum is removed. (A-11) The ECoG electrode is lifted off. (B-1) Cr is deposited on glass on substrate. (B-2) PSM is deposited on substrate. (B-3) PSM is patterned to define the outer geometry and the through-holes of the ECoG electrode. (B-4) Chromium/gold is deposited and the recording microelectrodes and hard wiring are patterned. (B-5) PSM is deposited again. (B-6) The outer geometry, the exposed recording microelectrode sites, and the through-holes of the ECoG electrode are patterned. (B-7) The ECoG electrode is lifted off. Large box at the bottom is a magnified illustration of a through-hole.

Mentions: Compared with conventional flexible materials, such as non-PSPI and poly (chloro-para-xylylene) (Parylene-C), PSPI provides similar good dielectrics with excellent thermal stability and high flexibility, good mechanical and electrical properties, and high chemical resistance as shown in Table 1. The important advantage of PSPI over more conventional polymers is that PSPI is a light-curable polymer, or in other words, a photosensitive material. This permits optimal light-curing conditions, which means only one photosensitive material is required for fabrication (details are described in Shrinkage Effect Of Curing Process of Results). An in vitro study (Sun et al., 2009) suggested that PSPI is not cytotoxic and does not induce adverse biological effects, which offers excellent long-term stability. As mentioned above, unlike other conventional flexible materials, PSPI does not need to be dry etched (Figure 1) for neural electrode fabrication. The elimination of the dry etching process simplifies the time-consuming processes requiring multilevel schemes (Figures 1A-5–A-9) and reduces equipment and maintenance cost. Photolithographic patterning is also advantageous in that the patterning substrate is not limited to one with a flat surface. Thus, PSPI allows flexible design architectures and fabrication of multichannel neural electrodes with more options for optimization of the configuration and size depending on the experimental purposes, with improvement of process yields.


Photosensitive-polyimide based method for fabricating various neural electrode architectures.

Kato YX, Furukawa S, Samejima K, Hironaka N, Kashino M - Front Neuroeng (2012)

Schematic diagram of the manufacturing process for the ECoG electrode with MEMS surface-micromachining technologies. Column (A): Conventional fabrication method for non-photosensitive material (non-PSM). Column (B): Fabrication method in this study for photosensitive material (PSM). Dry etching process is green color area from (A-5) to (A-9). (A-1) Cr is deposited on glass on substrate. (A-2) Non-PSM is deposited. (A-3) Chromium/gold is deposited and the recording microelectrodes and hard wiring are patterned. (A-4) Non-PSM is deposited again. (A-5) Aluminum is deposited as a mask for plasma etching. (A-6) Aluminum mask is patterned for the outer geometry and the through-holes of the ECoG electrode. (A-7) Non-PSM is patterned to define the outer geometry and the through-holes of the ECoG electrode by plasma etching. (A-8) Aluminum mask is patterned for the outer geometry, the exposed recording microelectrode sites, and the through-holes by plasma etching. (A-9) Non-PSM is patterned to expose the outer geometry, the exposed recording microelectrode sites, and the through-holes by plasma etching. (A-10) Aluminum is removed. (A-11) The ECoG electrode is lifted off. (B-1) Cr is deposited on glass on substrate. (B-2) PSM is deposited on substrate. (B-3) PSM is patterned to define the outer geometry and the through-holes of the ECoG electrode. (B-4) Chromium/gold is deposited and the recording microelectrodes and hard wiring are patterned. (B-5) PSM is deposited again. (B-6) The outer geometry, the exposed recording microelectrode sites, and the through-holes of the ECoG electrode are patterned. (B-7) The ECoG electrode is lifted off. Large box at the bottom is a magnified illustration of a through-hole.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376501&req=5

Figure 1: Schematic diagram of the manufacturing process for the ECoG electrode with MEMS surface-micromachining technologies. Column (A): Conventional fabrication method for non-photosensitive material (non-PSM). Column (B): Fabrication method in this study for photosensitive material (PSM). Dry etching process is green color area from (A-5) to (A-9). (A-1) Cr is deposited on glass on substrate. (A-2) Non-PSM is deposited. (A-3) Chromium/gold is deposited and the recording microelectrodes and hard wiring are patterned. (A-4) Non-PSM is deposited again. (A-5) Aluminum is deposited as a mask for plasma etching. (A-6) Aluminum mask is patterned for the outer geometry and the through-holes of the ECoG electrode. (A-7) Non-PSM is patterned to define the outer geometry and the through-holes of the ECoG electrode by plasma etching. (A-8) Aluminum mask is patterned for the outer geometry, the exposed recording microelectrode sites, and the through-holes by plasma etching. (A-9) Non-PSM is patterned to expose the outer geometry, the exposed recording microelectrode sites, and the through-holes by plasma etching. (A-10) Aluminum is removed. (A-11) The ECoG electrode is lifted off. (B-1) Cr is deposited on glass on substrate. (B-2) PSM is deposited on substrate. (B-3) PSM is patterned to define the outer geometry and the through-holes of the ECoG electrode. (B-4) Chromium/gold is deposited and the recording microelectrodes and hard wiring are patterned. (B-5) PSM is deposited again. (B-6) The outer geometry, the exposed recording microelectrode sites, and the through-holes of the ECoG electrode are patterned. (B-7) The ECoG electrode is lifted off. Large box at the bottom is a magnified illustration of a through-hole.
Mentions: Compared with conventional flexible materials, such as non-PSPI and poly (chloro-para-xylylene) (Parylene-C), PSPI provides similar good dielectrics with excellent thermal stability and high flexibility, good mechanical and electrical properties, and high chemical resistance as shown in Table 1. The important advantage of PSPI over more conventional polymers is that PSPI is a light-curable polymer, or in other words, a photosensitive material. This permits optimal light-curing conditions, which means only one photosensitive material is required for fabrication (details are described in Shrinkage Effect Of Curing Process of Results). An in vitro study (Sun et al., 2009) suggested that PSPI is not cytotoxic and does not induce adverse biological effects, which offers excellent long-term stability. As mentioned above, unlike other conventional flexible materials, PSPI does not need to be dry etched (Figure 1) for neural electrode fabrication. The elimination of the dry etching process simplifies the time-consuming processes requiring multilevel schemes (Figures 1A-5–A-9) and reduces equipment and maintenance cost. Photolithographic patterning is also advantageous in that the patterning substrate is not limited to one with a flat surface. Thus, PSPI allows flexible design architectures and fabrication of multichannel neural electrodes with more options for optimization of the configuration and size depending on the experimental purposes, with improvement of process yields.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Brain Science Institute, Tamagawa University, Machida Tokyo, Japan.

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.

No MeSH data available.