FIGURE 10.

Electrode noise: (A,B) Noise power spectral density (PSD) of Pt-electrodes and Pt-black electrodes computed from the real part of the measured electrode impedance. The electrodes show 1/f noise characteristics at low frequencies and reach a plateau of thermal noise at higher frequencies. After Pt-black deposition, the noise spectral density was significantly reduced and reached a plateau defined by the spreading resistance (which depends on the electrode geometric area and solution resistance). (C–E) Integrated noise (μV_rms) of the electrodes in the AP region, LFP region, and over the full bandwidth (1 Hz to 5 kHz) versus electrode size and comparison to measurement results obtained with four electrode sizes (el1: 86 μm²; el2: 44 μm²; el3: 22 μm²; el4: 11 μm²) on an HD-MEA. For bright Pt electrodes, the noise in the LFP band increased from 5 μV_rms to 23 μV_rms for going from a 100 × 100 μm² size electrode to a 1 × 1 μm² size electrode. In the AP band, the noise increase was less, only from 3 μV_rms to 13 μV_rms. After Pt-black deposition, the LFP noise and AP noise was below 8 μV_rms for all electrode sizes.