SEM/EDS Characterisation of MEA Substrates with 3D Microtopography: Composition Uniformity Metrics and Salt-Residue Coverage

This study presents the characterisation of microelectrode array (MEA) chips with 3D microtopography using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The aim was to evaluate the uniformity of the composition across four microtopographic zones and between individual chips, as well as to assess surface coverage following the drying of Neurobasal-A (NB-A) culture medium. The atomic fractions of the chip elements were expressed by the titanium ratio (Tiᵢndex) on three chips. The residue coverage of the chip surface with dried NB-A droplets on a four-chip sample (3 or 30 L; two chips per volume) was expressed by NaClᵢndex (Na and Cl relative to chip-related elements). A twofactor ANOVA test showed a tendency for the Tiᵢndex to vary across zones rather than between chips, implying a high-quality manufacturing process. The NaClᵢndex increased with the volume of the culture medium without a noticeable effect across zones, indicating that the dried medium may mask the microstructures of the chip surface.