Figure 3

The z-distance between the micropipette and the HD-MEA can be estimated according to the electrical potential spatial distribution. (a) Exemplary potential spatial decay for a z-distance of the point source of 50 μm including experimental data (gray dots), and data derived from a method-of-images or MoI model (pink line) and a finite-element or FEM model (blue line). The differences between the FEM and MoI values are displayed as a blue dashed line. The gray dots represent potential values measured through the 11’000 electrodes shown in Fig. 1c. (b) Experimentally determined potential spatial distributions, normalized to the maximum potential value per z-distance. (c) Residuals computed by subtracting the normalized potential spatial decays of experiments and models: MoI (left) and FEM (right). In general, the FEM model residuals are closer to zero. (d,e) Comparison of potential spatial decays according to the area under the curve (Area), computed by numerical integration over the interval of 1 to 1000 μm distance from the peak value. The Area provides information on the steepness of the curve: the slope is infinite if the Area is zero and the slope is zero if the Area is 1000. (d) Two MoI-based potential spatial decays (normalized) for z-distances of 20 μm (i) and 100 μm (ii), are plotted and the computed Area values amounted to 83 and 452, respectively. (e) Values of Area computed for z-distances between 20 and 1000 μm, based on normalized potential spatial decays obtained from experiments, MoI, and FEM. Area values derived from the FEM model were closer to the experimental results.