ISBN 978-3-8439-5460-0

978-3-8439-5460-0, Reihe Mikrosystemtechnik

Helen Steins
A Flexible Protruding Microelectrode Array for Visceral Neuromodulation

220 Seiten, Dissertation Albert-Ludwigs-Universität Freiburg im Breisgau (2023), Softcover, B5

Zusammenfassung / Abstract

Selectively addressing delicate autonomic nerves requires the development of small and flexible technical interfaces that incorporate innovative designs and manufacturing techniques.

In this thesis, the development of a three-dimensional (3D) protruding thin-film microelectrode array (MEA) is presented for recording small-amplitude neural signal from visceral structures with the aim of treating digestive diseases. By penetrating the target nerves transversely, the distance to the axons is reduced, thereby increasing the signal-to-noise ratio.

High-aspect-ratio gold pillars (Ø 20 µm or 50 µm, ~60 µm height) were electrodeposited on a micromachined polyimide substrate using a photoresist template. Passivating the pillar sidewalls with Parylene C and subsequently modifying the pillar heads by wet etching and the deposition of a titanium nitride coating resulted in microelectrodes with low impedances (~7 kΩ at 1 kHz for a Ø 50 µm microelectrode with an exposed surface area of ~5000 µm²) and low intrinsic noise levels.

The MEA was validated in ex vivo studies on mouse retina in which spontaneous action potentials were measured. In acute experiments with pigs, evoked C-fibre responses were recorded from autonomic target structures, such as the abdominal vagus nerve and the hypogastric plexus. Moreover, this thesis presents a process for modifying pillar-shaped microelectrodes into cones by wet chemical etching to further increase their selectivity and mechanical stability while minimising their invasiveness.

The thin-film 3D neural interface can be used for the study of in vitro cell cultures as well as for the investigation of neural circuits and the development of stimulation strategies in bioelectronic medicine.