Fabrication and characterization of polyimide-based 'smooth' titanium nitride microelectrode arrays for neural stimulation and recording

Fabrication and characterization of polyimide-based 'smooth' titanium nitride microelectrode arrays for neural stimulation and recording

Oliveira Rodrigues, F.J. (TU Delft Electronic Components, Technology and Materials; University of Minho)
Ribeiro, J.F. (University of Minho)
Anacleto, P.A. (University of Minho)
Fouchard, A. (Grenoble Institute of Neurosciences)
David, O. (Grenoble Institute of Neurosciences)
Sarro, Pasqualina M (TU Delft Electronic Components, Technology and Materials)
Mendez, P.M. (University of Minho)

2019

OBJECTIVE: As electrodes are required to interact with sub-millimeter neural structures, innovative microfabrication processes are required to enable fabrication of microdevices involved in such stimulation and/or recording. This requires the development of highly integrated and miniaturized systems, comprising die-integration-compatible technology and flexible microelectrodes. To elicit selective stimulation and recordings of sub-neural structures, such microfabrication process flow can beneficiate from the integration of titanium nitride (TiN) microelectrodes onto a polyimide substrate. Finally, assembling onto cuffs is required, as well as electrode characterization. APPROACH: Flexible TiN microelectrode array integration and miniaturization was achieved through microfabrication technology based on microelectromechanical systems (MEMS) and complementary metal-oxide semiconductor processing techniques and materials. They are highly reproducible processes, granting extreme control over the feature size and shape, as well as enabling the integration of on-chip electronics. This design is intended to enhance the integration of future electronic modules, with high gains on device miniaturization. MAIN RESULTS: (a) Fabrication of two electrode designs, (1) 2 mm long array with 14 TiN square-shaped microelectrodes (80  ×  80 µm2), and (2) an electrode array with 2 mm  ×  80 µm contacts. The average impedances at 1 kHz were 59 and 5.5 kΩ, respectively, for the smaller and larger contacts. Both designs were patterned on a flexible substrate and directly interconnected with a silicon chip. (b) Integration of flexible microelectrode array onto a cuff electrode designed for acute stimulation of the sub-millimeter nerves. (c) The TiN electrodes exhibited capacitive charge transfer, a water window of  -0.6 V to 0.8 V, and a maximum charge injection capacity of 154  ±  16 µC cm-2. SIGNIFICANCE: We present the concept, fabrication and characterization of composite and flexible cuff electrodes, compatible with post-processing and MEMS packaging technologies, which allow for compact integration with control, readout and RF electronics. The fabricated TiN microelectrodes were electrochemically characterized and exhibited a comparable performance to other state-of-the-art electrodes for neural stimulation and recording. Therefore, the presented TiN-on-polyimide microelectrodes, released from silicon wafers, are a promising solution for neural interfaces targeted at sub-millimeter nerves, which may benefit from future upgrades with die-electronic modules.

peripheral nerve interfaces
nerve cuff electrodes
die-compatible process
titanium nitride electrode
polyimide composite electrodes
sub-millimeter nerves

http://resolver.tudelft.nl/uuid:0d29dedb-0554-4e84-8167-e63a472ca874

https://doi.org/10.1088/1741-2552/ab4dbb

2021-08-02

1741-2560

Journal of Neural Engineering, 17 (2020) (1), 1-15

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2019 F.J. Oliveira Rodrigues, J.F. Ribeiro, P.A. Anacleto, A. Fouchard, O. David, Pasqualina M Sarro, P.M. Mendez