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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

(A) Amplitude of the stimulation artifact on the three types of plated and unplated electrodes after ten 10-μs pulses are delivered. Mean ± standard error values on the four electrodes of each type of plating are shown graphically. Values in parentheses show the mean.**p < 0.005 compared to unplated electrodes; #p < 0.27 compared to pulsed plated and DC plated electrodes. (B) Duration of the stimulation artifacts with mean in parentheses and error bars showing standard error.**p < 0.01 compared to unplated electrodes; #p < 0.07 compared to pulsed plated and sonicoplated electrodes.
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Figure 8: (A) Amplitude of the stimulation artifact on the three types of plated and unplated electrodes after ten 10-μs pulses are delivered. Mean ± standard error values on the four electrodes of each type of plating are shown graphically. Values in parentheses show the mean.**p < 0.005 compared to unplated electrodes; #p < 0.27 compared to pulsed plated and DC plated electrodes. (B) Duration of the stimulation artifacts with mean in parentheses and error bars showing standard error.**p < 0.01 compared to unplated electrodes; #p < 0.07 compared to pulsed plated and sonicoplated electrodes.

Mentions: Extracellular electrical stimuli (∼1 V) are typically five orders of magnitude larger than extracellularly recorded neural signals (∼10 μV). This makes recording spikes evoked by stimuli difficult due to large stimulation artifacts. Capacitive charge accumulation between the stimulating electrode and the surrounding tissue impedes or prevents the detection of spikes for the time period for which the stimulation artifacts persist. In many cases, recording electronics become saturated for tens of milliseconds post stimulation (Rolston et al., 2009). As shown in Figure 7, a substantial reduction in the impedance on the stimulating electrode can reduce stimulation artifacts to a great extent. Since the sonicoplated electrodes require the lowest voltage for a 10 μA stimulus, compared to the other types of plating, they have the least stimulation artifact (in terms of amplitude and duration). The amplitudes and durations of the stimulation artifacts for the different types of plated electrodes compared to the unplated electrodes are quantified in Figure 8. The durations of the artifacts were reduced to about 8.6 ms on the sonicoplated electrodes compared to 482 ms in the unplated case. This is a 98% reduction in the duration of stimulation artifacts on the sonicoplated electrodes (p < 0.01). The amplitude of the artifacts was also reduced by 83% (p < 0.005). Similar reductions were observed on the unplated and DC plated electrodes too, but the results were best on the sonicoplated electrodes. These results were obtained in vivo, 20 days after implantation.


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)

(A) Amplitude of the stimulation artifact on the three types of plated and unplated electrodes after ten 10-μs pulses are delivered. Mean ± standard error values on the four electrodes of each type of plating are shown graphically. Values in parentheses show the mean.**p < 0.005 compared to unplated electrodes; #p < 0.27 compared to pulsed plated and DC plated electrodes. (B) Duration of the stimulation artifacts with mean in parentheses and error bars showing standard error.**p < 0.01 compared to unplated electrodes; #p < 0.07 compared to pulsed plated and sonicoplated electrodes.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: (A) Amplitude of the stimulation artifact on the three types of plated and unplated electrodes after ten 10-μs pulses are delivered. Mean ± standard error values on the four electrodes of each type of plating are shown graphically. Values in parentheses show the mean.**p < 0.005 compared to unplated electrodes; #p < 0.27 compared to pulsed plated and DC plated electrodes. (B) Duration of the stimulation artifacts with mean in parentheses and error bars showing standard error.**p < 0.01 compared to unplated electrodes; #p < 0.07 compared to pulsed plated and sonicoplated electrodes.
Mentions: Extracellular electrical stimuli (∼1 V) are typically five orders of magnitude larger than extracellularly recorded neural signals (∼10 μV). This makes recording spikes evoked by stimuli difficult due to large stimulation artifacts. Capacitive charge accumulation between the stimulating electrode and the surrounding tissue impedes or prevents the detection of spikes for the time period for which the stimulation artifacts persist. In many cases, recording electronics become saturated for tens of milliseconds post stimulation (Rolston et al., 2009). As shown in Figure 7, a substantial reduction in the impedance on the stimulating electrode can reduce stimulation artifacts to a great extent. Since the sonicoplated electrodes require the lowest voltage for a 10 μA stimulus, compared to the other types of plating, they have the least stimulation artifact (in terms of amplitude and duration). The amplitudes and durations of the stimulation artifacts for the different types of plated electrodes compared to the unplated electrodes are quantified in Figure 8. The durations of the artifacts were reduced to about 8.6 ms on the sonicoplated electrodes compared to 482 ms in the unplated case. This is a 98% reduction in the duration of stimulation artifacts on the sonicoplated electrodes (p < 0.01). The amplitude of the artifacts was also reduced by 83% (p < 0.005). Similar reductions were observed on the unplated and DC plated electrodes too, but the results were best on the sonicoplated electrodes. These results were obtained in vivo, 20 days after implantation.

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