Figure 1. Nanopillar electrode devices and their interactions with HL-1 cardiomyocytes.

(a) An optical image of a nanopillar electrode device with 4-by-4 Pt pads and leads connected to recording amplifiers. (b) An SEM image of an array of five 150 nm-diameter, 1.5 μm-long vertical nanopillar electrodes on the Pt pad as shown in (a). Most of the nanopillar electrode surface is exposed for measuring cell electrophysiology but the rest of the pads and leads are electrically insulated by a 350 nm Si₃N₄/SiO₂ layer. The footprint of the nanopillar electrode array on each pad is 5 × 5 μm² or less. Inset shows schematics of fabricated pillar. (c) Optical image of HL-1 cells cultured on a glass coverslip with four 5-nanopillar electrode arrays without the underlying Pt pads. Cells growing on vertical nanopillar electrodes show similar morphology to those on planar areas. (d) An SEM image shows four 5-nanopillar electrode arrays covered by an HL-1 cell. Arrows indicate the locations of nanopillar electrodes. (e) The cell-nanopillar electrode interface exposed by FIB milling shows that the nanopillar electrode is fully engulfed by the cell. (f) An SEM image shows cellular protrudings reaching out to the nanopillar electrodes. All SEM images are taken at 52 degrees with respect to normal.