Figure 1.
Microelectrodes designed and manufactured at Fraunhofer Institute for Biomedical Engineering (IBMT): (I) Pt foil, (II) Pt epimysial, (III) graphene printed, (IV) Pt printed, (V) Pt cuff, (VI) microporous Pt cuff, (VII) DS-File.
Figure 1.
Microelectrodes designed and manufactured at Fraunhofer Institute for Biomedical Engineering (IBMT): (I) Pt foil, (II) Pt epimysial, (III) graphene printed, (IV) Pt printed, (V) Pt cuff, (VI) microporous Pt cuff, (VII) DS-File.
Figure 2.
SEM image of a printed graphene electrode F with 20 µm resolution.
Figure 2.
SEM image of a printed graphene electrode F with 20 µm resolution.
Figure 3.
SEM image of a printed graphene electrode F with 10 µm resolution.
Figure 3.
SEM image of a printed graphene electrode F with 10 µm resolution.
Figure 4.
Simplified diagram of the voltage transient (VT) measurement setup used in our lab. WE, RE, and CE represent the working, reference, and counter electrodes, respectively.
Figure 4.
Simplified diagram of the voltage transient (VT) measurement setup used in our lab. WE, RE, and CE represent the working, reference, and counter electrodes, respectively.
Figure 5.
Maximum reversible charge injection capacity (CIC) as a function of the pulse width of the stimulation signal.
Figure 5.
Maximum reversible charge injection capacity (CIC) as a function of the pulse width of the stimulation signal.
Figure 6.
Incremental changes of the CIC when round electrode dimensions become smaller. Black line: round epimysial electrodes B, C, D; Red line: Pt foil square electrode A.
Figure 6.
Incremental changes of the CIC when round electrode dimensions become smaller. Black line: round epimysial electrodes B, C, D; Red line: Pt foil square electrode A.
Figure 7.
CIC of the foil Pt square electrodes A as a function of the electrode area for three different pulse widths of the stimulation signal.
Figure 7.
CIC of the foil Pt square electrodes A as a function of the electrode area for three different pulse widths of the stimulation signal.
Figure 8.
CIC of the epimysial sputtered Pt round electrodes B, C and D as a function of the electrode area for three different pulse widths of the stimulation signal.
Figure 8.
CIC of the epimysial sputtered Pt round electrodes B, C and D as a function of the electrode area for three different pulse widths of the stimulation signal.
Figure 9.
Increase of the delivered charge because of a higher roughness factor for a pulse width of 200 µs.
Figure 9.
Increase of the delivered charge because of a higher roughness factor for a pulse width of 200 µs.
Figure 10.
Increase of the CSCc because of a higher roughness factor.
Figure 10.
Increase of the CSCc because of a higher roughness factor.
Figure 11.
Decrease of the low frequency electrode impedance because of a higher roughness factor.
Figure 11.
Decrease of the low frequency electrode impedance because of a higher roughness factor.
Figure 12.
Extreme polarization for the Pt cuff electrode G in PBS and NaCl solutions, using a stimulation signal of 200 µs.
Figure 12.
Extreme polarization for the Pt cuff electrode G in PBS and NaCl solutions, using a stimulation signal of 200 µs.
Figure 13.
Cyclic voltammetry (CV) of the Pt cuff electrode G in PBS and NaCl solutions.
Figure 13.
Cyclic voltammetry (CV) of the Pt cuff electrode G in PBS and NaCl solutions.
Figure 14.
Impedance of the Pt cuff electrode G in PBS and NaCl solutions.
Figure 14.
Impedance of the Pt cuff electrode G in PBS and NaCl solutions.
Figure 15.
Impedance of the Pt cuff electrode G in NaCl at room temperature.
Figure 15.
Impedance of the Pt cuff electrode G in NaCl at room temperature.
Figure 16.
CIC of the Pt cuff electrode G over time.
Figure 16.
CIC of the Pt cuff electrode G over time.
Figure 17.
CV of the Pt cuff electrode G in NaCl at room temperature.
Figure 17.
CV of the Pt cuff electrode G in NaCl at room temperature.
Figure 18.
CV of the graphene electrode F in NaCl solution.(scan rate = 100 mV, scan number = 5).
Figure 18.
CV of the graphene electrode F in NaCl solution.(scan rate = 100 mV, scan number = 5).
Figure 19.
Extreme polarization potentials for the graphene electrode F before and after the activation using a stimulation signal of 200 µs.
Figure 19.
Extreme polarization potentials for the graphene electrode F before and after the activation using a stimulation signal of 200 µs.
Figure 20.
CIC of the graphene electrode F as a function of the pulse width of the stimulation signal. Red line: before the activation; Black line: after the activation.
Figure 20.
CIC of the graphene electrode F as a function of the pulse width of the stimulation signal. Red line: before the activation; Black line: after the activation.
Table 1.
Microelectrodes characterized in the present study. GSA = geometric surface area.
Table 1.
Microelectrodes characterized in the present study. GSA = geometric surface area.
Microelectrode | Type | Material | Shape | GSA (cm2) |
---|
A | Foil | Pt | Square | 0.3025 |
B | Epimysial | Sputtered Pt | Round | 0.001963 |
C | Epimysial | Sputtered Pt | Round | 0.007854 |
D | Epimysial | Sputtered Pt | Round | 0.031416 |
E | Print | Sputtered Pt | Round | 0.007854 |
F | Print | Graphene | Round | 0.007854 |
G | Cuff | Sputtered Pt | Ellipse | 0.0013 |
H | Cuff | Microporous Pt | Ellipse | 0.0013 |
I | Cuff | Microporous Pt | Rectangular | 0.0195 |
J | DS-File | Microporous Pt | Round | 0.004 |
K | DS-File | Microporous Pt | Round | 0.00006963742 |
Table 2.
Comparison of the CIC of electrodes A and D with similar dimensions, but different roughness factors.
Table 2.
Comparison of the CIC of electrodes A and D with similar dimensions, but different roughness factors.
Microelectrodes | Roughness Factor | GSA (cm2) | CIC 200 µs (µC/cm2) | CIC 300 µs (µC/cm2) | CIC 500 µs (µC/cm2) |
---|
A | >1 | 0.3025 | 10.08 | 12.33 | 16.91 |
D | 1 | 0.3114 | 15.37 | 18.54 | 21.61 |
Table 3.
Characteristic values of Pt cuff electrodes G and H with the same shape and size, but different roughness factors. ESA = effective surface area; CSCc = cathodal charge-storage capacity.
Table 3.
Characteristic values of Pt cuff electrodes G and H with the same shape and size, but different roughness factors. ESA = effective surface area; CSCc = cathodal charge-storage capacity.
Electrode | Material | GSA/ESA | CIC (µC/cm2) | CSCc (mC/cm2) | Rs (Ω) |
---|
G | Pt | 1 | 81.63 | 3.69532 | 884.8 |
H | Microporous Pt | >1 | 295.9 | 37.6721 | 770 |
Table 4.
Formulation of phosphate-buffered saline (PBS) and NaCl solutions.
Table 4.
Formulation of phosphate-buffered saline (PBS) and NaCl solutions.
| PBS | NaCl |
---|
| 8000 | 9000 |
| 200 | - |
| 200 | - |
| 2160 | - |
Table 5.
Values of the cuff electrode G in PBS and NaCl solutions.
Table 5.
Values of the cuff electrode G in PBS and NaCl solutions.
Solution | CIC (µC/cm2) | CSCc (mC/cm2) | Water Window (V) |
---|
NaCl | 81,63 | 3,695 | [−0.6, 0.9] |
PBS | 97,76 | 6,409 | [−0.75, 1.2] |
Table 6.
Results at the beginning and end of the continuous pulse test for the cuff electrode G.
Table 6.
Results at the beginning and end of the continuous pulse test for the cuff electrode G.
| CIC (µC/cm2) | CSCc (mC/cm2) |
---|
Initial (t = 0 hours) | 57.97 | 3.695 |
Final (t = 172 hours) | 83.38 | 14.86 |
Table 7.
CIC of the graphene printed electrode F and Pt printed electrode E for different values of pulse width.
Table 7.
CIC of the graphene printed electrode F and Pt printed electrode E for different values of pulse width.
| CIC 200µs (µC/cm2) | CIC 300µs (µC/cm2) | CIC 500µs (µC/cm2) |
---|
Graphene electrode F before activation | 55.9 | 71.05 | 106.84 |
Graphene electrode F after activation | 428.9 | 542.3 | 813.6 |
Graphene electrode F 5 weeks after activation | 145.7 | 177.3 | 242.8 |
Pt printed electrode E | 23.83 | 25.48 | 29.92 |
Table 8.
CIC and CSCc of all electrodes of our study, sorted by decreasing CIC.
Table 8.
CIC and CSCc of all electrodes of our study, sorted by decreasing CIC.
Microelectrode | Type | Material | Area (cm2) | CIC (µC/cm2) | CSCc (mC/cm2) |
---|
F | Print | Graphene | 0.007854 | 428.9 | 31.2806 |
H | Cuff | Microporous Pt | 0.0013 | 295 | 37.6721 |
K | DS-File | Microporous Pt | 0.00006963742 | 231.2 | 9.88699 |
I | Cuff | Microporous Pt | 0.0195 | 166.9 | 29.6721 |
J | DS-File | Microporous Pt | 0.004 | 122.7 | 15.4088 |
G | Cuff | Sputtered Pt | 0.0013 | 81.63 | 3.69532 |
B | Epimysial | Sputtered Pt | 0.001963 | 26.06 | 6.26489 |
E | Print | Sputtered Pt | 0.007854 | 23.68 | 3.19265 |
C | Epimysial | Sputtered Pt | 0.007854 | 19.78 | 2.42284 |
D | Epimysial | Sputtered Pt | 0.031416 | 15.37 | 0.211339 |
A | Foil | Pt | 0.3025 | 10.08 | 1.8863 |