What is an electrode's impedance, and does a low impedance make it more biocompatible? · Lobeworks/17

Impedance is how much the electrode opposes a signal that changes in time, resistance generalised to moving signals; for the capacitive double layer ∣Z∣=1/(2πfC)|Z| = 1/(2\pi f C)∣Z∣=1/(2πfC), so more capacitance means lower impedance.

What is an electrode's impedance, and does a low impedance make it more biocompatible?

Impedance is how much the electrode opposes a signal that changes in time, resistance generalised to moving signals; for the capacitive double layer ∣Z∣=1/(2πfC)|Z| = 1/(2\pi f C)∣Z∣=1/(2πfC), so more capacitance means lower impedance. Low impedance means less thermal noise (vn=4kTR Δfv_n = \sqrt{4kTR,\Delta f}vn​=4kTRΔf​) and less signal lost before the amplifier. It does not make the electrode more biocompatible: that is the tissue's reaction to material, shape and movement, a separate property.