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Improving impedance of implantable microwire multi-electrode arrays by ultrasonic electroplating of durable platinum black.

Desai SA, Rolston JD, Guo L, Potter SM - Front Neuroeng (2010)

Bottom Line: However, because of the low durability of Pt black plating, this method has not been popular for chronic use.Sonicoplating (i.e. electroplating under ultrasonic agitation) has been shown to improve the durability of Pt black on the base metals of macro-electrodes used for cyclic voltammetry.We show here that sonicoplating can lower the impedances of microwire multi-electrode arrays (MMEA) by an order of magnitude or more (depending on the time and voltage of electroplating), with better durability compared to pulsed plating or traditional DC methods.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Neuroengineering, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology Atlanta, GA, USA.

ABSTRACT
Implantable microelectrode arrays (MEAs) have been a boon for neural stimulation and recording experiments. Commercially available MEAs have high impedances, due to their low surface area and small tip diameters, which are suitable for recording single unit activity. Lowering the electrode impedance, but preserving the small diameter, would provide a number of advantages, including reduced stimulation voltages, reduced stimulation artifacts and improved signal-to-noise ratio. Impedance reductions can be achieved by electroplating the MEAs with platinum (Pt) black, which increases the surface area but has little effect on the physical extent of the electrodes. However, because of the low durability of Pt black plating, this method has not been popular for chronic use. Sonicoplating (i.e. electroplating under ultrasonic agitation) has been shown to improve the durability of Pt black on the base metals of macro-electrodes used for cyclic voltammetry. This method has not previously been characterized for MEAs used in chronic neural implants. We show here that sonicoplating can lower the impedances of microwire multi-electrode arrays (MMEA) by an order of magnitude or more (depending on the time and voltage of electroplating), with better durability compared to pulsed plating or traditional DC methods. We also show the improved stimulation and recording performance that can be achieved in an in vivo implantation study with the sonicoplated low-impedance MMEAs, compared to high-impedance unplated electrodes.

No MeSH data available.


Related in: MedlinePlus

Mean impedance spectra of the three types of plated and unplated electrodes in an in vivo MMEA immediately after implantation (A) and after 6 (B), 14 (C) and 20 (D) days.
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Figure 4: Mean impedance spectra of the three types of plated and unplated electrodes in an in vivo MMEA immediately after implantation (A) and after 6 (B), 14 (C) and 20 (D) days.

Mentions: In order to look at the improvements that reducing impedance can have in an actual recording and stimulation experiment and also to look at the durability of Pt black plating in a chronic study, we implanted an electroplated MMEA (according to the method in the “Electroplating Setup” section, with no sonication of pulsed or DC plated electrodes) into a rat's hippocampus and followed the impedances over a period of three weeks. As seen from Figure 4, the difference in the impedances between the three types of plating was not as noticeable as in our durability test in saline. However, it should be noted that the impedances in an in vivo environment are affected by variable factors such as gliosis (Rudge et al., 1989; Polikov et al., 2005) making it difficult to follow the impedance contributions of the electrodes themselves. The impedances on the plated electrodes remained significantly lower than the unplated electrodes at 3 weeks post implantation (p < 0.001, t-test). In fact, the sonicoplated electrodes had, on average, lower impedances than electrodes with other types of plating, throughout the course of three weeks (p < 0.35).


Improving impedance of implantable microwire multi-electrode arrays by ultrasonic electroplating of durable platinum black.

Desai SA, Rolston JD, Guo L, Potter SM - Front Neuroeng (2010)

Mean impedance spectra of the three types of plated and unplated electrodes in an in vivo MMEA immediately after implantation (A) and after 6 (B), 14 (C) and 20 (D) days.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2871717&req=5

Figure 4: Mean impedance spectra of the three types of plated and unplated electrodes in an in vivo MMEA immediately after implantation (A) and after 6 (B), 14 (C) and 20 (D) days.
Mentions: In order to look at the improvements that reducing impedance can have in an actual recording and stimulation experiment and also to look at the durability of Pt black plating in a chronic study, we implanted an electroplated MMEA (according to the method in the “Electroplating Setup” section, with no sonication of pulsed or DC plated electrodes) into a rat's hippocampus and followed the impedances over a period of three weeks. As seen from Figure 4, the difference in the impedances between the three types of plating was not as noticeable as in our durability test in saline. However, it should be noted that the impedances in an in vivo environment are affected by variable factors such as gliosis (Rudge et al., 1989; Polikov et al., 2005) making it difficult to follow the impedance contributions of the electrodes themselves. The impedances on the plated electrodes remained significantly lower than the unplated electrodes at 3 weeks post implantation (p < 0.001, t-test). In fact, the sonicoplated electrodes had, on average, lower impedances than electrodes with other types of plating, throughout the course of three weeks (p < 0.35).

Bottom Line: However, because of the low durability of Pt black plating, this method has not been popular for chronic use.Sonicoplating (i.e. electroplating under ultrasonic agitation) has been shown to improve the durability of Pt black on the base metals of macro-electrodes used for cyclic voltammetry.We show here that sonicoplating can lower the impedances of microwire multi-electrode arrays (MMEA) by an order of magnitude or more (depending on the time and voltage of electroplating), with better durability compared to pulsed plating or traditional DC methods.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Neuroengineering, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology Atlanta, GA, USA.

ABSTRACT
Implantable microelectrode arrays (MEAs) have been a boon for neural stimulation and recording experiments. Commercially available MEAs have high impedances, due to their low surface area and small tip diameters, which are suitable for recording single unit activity. Lowering the electrode impedance, but preserving the small diameter, would provide a number of advantages, including reduced stimulation voltages, reduced stimulation artifacts and improved signal-to-noise ratio. Impedance reductions can be achieved by electroplating the MEAs with platinum (Pt) black, which increases the surface area but has little effect on the physical extent of the electrodes. However, because of the low durability of Pt black plating, this method has not been popular for chronic use. Sonicoplating (i.e. electroplating under ultrasonic agitation) has been shown to improve the durability of Pt black on the base metals of macro-electrodes used for cyclic voltammetry. This method has not previously been characterized for MEAs used in chronic neural implants. We show here that sonicoplating can lower the impedances of microwire multi-electrode arrays (MMEA) by an order of magnitude or more (depending on the time and voltage of electroplating), with better durability compared to pulsed plating or traditional DC methods. We also show the improved stimulation and recording performance that can be achieved in an in vivo implantation study with the sonicoplated low-impedance MMEAs, compared to high-impedance unplated electrodes.

No MeSH data available.


Related in: MedlinePlus