Fabrication and Characterization of an Upside-Down Carbon Nanotube Microelectrode Array

Microelectrode arrays (MEAs) are widely used in biological application to locally stimulate and record the electrical activity of living cells. Here, a novel fabrication process for a carbon nanotube (CNT)-based MEA integrated on the backside of a free standing stretchable membrane is reported. The new process flow overcomes the manually intensive procedures used in the previous works. The microfabricated upside-down CNT MEA consists of microelectrodes with an area of 110 $\mu \text{m}^{2}$ covered with cobalt-grown CNTs. The surface area enhancement and the foam-like morphology of the CNTs allow an increase of the charge injection per unit area at the electrode-electrolyte interface, resulting in a significantly lower electrochemical impedance of the electrodes. In particular, at 1 kHz, the fabricated CNT-MEA electrodes show a reduction of the overall impedance up to 96% in comparison with benchmark TiN electrodes. The obtained results confirm the effectiveness of the proposed surface texturing through CNT integration. Moreover, the quality and the morphology as well as the biocompatibility of the fabricated CNT-based electrodes were assessed. The obtained results demonstrate that significant improvement can be achieved by integrating structured nanoporous material on MEAs.