Passivated electrode side walls by atomic layer deposition on flexible polyimide based samples

Westerhausen, Markus; Martin, Tanja; Metzger, Michael; Blendinger, Felix; Fleischer, Monika; Hofmann, Boris; Bucher, Volker

doi:10.1016/j.mee.2020.111315

Cited by 7 publications

(7 citation statements)

References 23 publications

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“…As the development of miniaturized structures progresses to the nanoscale, further innovative passivation coatings need to be considered. Thin-film metal oxide coatings applied by Atomic Layer Deposition (ALD) are gaining attention as ultrathin conformal coatings with high barrier properties [79][80][81] .…”

Section: Optical and Electrical Characterization Of The 3d Microelect...mentioning

confidence: 99%

A flexible protruding microelectrode array for neural interfacing in bioelectronic medicine

et al. 2022

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Recording neural signals from delicate autonomic nerves is a challenging task that requires the development of a low-invasive neural interface with highly selective, micrometer-sized electrodes. This paper reports on the development of a three-dimensional (3D) protruding thin-film microelectrode array (MEA), which is intended to be used for recording low-amplitude neural signals from pelvic nervous structures by penetrating the nerves transversely to reduce the distance to the axons. Cylindrical gold pillars (Ø 20 or 50 µm, ~60 µm height) were fabricated on a micromachined polyimide substrate in an electroplating process. Their sidewalls were insulated with parylene C, and their tips were optionally modified by wet etching and/or the application of a titanium nitride (TiN) coating. The microelectrodes modified by these combined techniques exhibited low impedances (~7 kΩ at 1 kHz for Ø 50 µm microelectrode with the exposed surface area of ~5000 µm²) and low intrinsic noise levels. Their functionalities were evaluated in an ex vivo pilot study with mouse retinae, in which spontaneous neuronal spikes were recorded with amplitudes of up to 66 µV. This novel process strategy for fabricating flexible, 3D neural interfaces with low-impedance microelectrodes has the potential to selectively record neural signals from not only delicate structures such as retinal cells but also autonomic nerves with improved signal quality to study neural circuits and develop stimulation strategies in bioelectronic medicine, e.g., for the control of vital digestive functions.

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Section: Optical and Electrical Characterization Of The 3d Microelect...mentioning

confidence: 99%

A flexible protruding microelectrode array for neural interfacing in bioelectronic medicine

et al. 2022

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“…Hard etch masks are required for this dry etch process, as thin photoresist layers lack the etch selectivity required to allow the polyimide layer to be etched before the mask itself is etched away completely. Examples of etch mask materials include aluminium [53], chromium [54], titanium [50], nickel [55] and gold [56], although in some cases thick photoresist may also be used.…”

Section: Polymer Patterningmentioning

confidence: 99%

Cleanroom strategies for micro- and nano-fabricating flexible implantable neural electronics

Walton

Cerezo-Sánchez

McGlynn

et al. 2022

Phil. Trans. R. Soc. A.

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Implantable electronic neural interfaces typically take the form of probes and are made with rigid materials such as silicon and metals. These have advantages such as compatibility with integrated microchips, simple implantation and high-density nanofabrication but tend to be lacking in terms of biointegration, biocompatibility and durability due to their mechanical rigidity. This leads to damage to the device or, more importantly, the brain tissue surrounding the implant. Flexible polymer-based probes offer superior biocompatibility in terms of surface biochemistry and better matched mechanical properties. Research which aims to bring the fabrication of electronics on flexible polymer substrates to the nano-regime is remarkably sparse, despite the push for flexible consumer electronics in the last decade or so. Cleanroom-based nanofabrication techniques such as photolithography have been used as pattern transfer methods by the semiconductor industry to produce single nanometre scale devices and are now also used for making flexible circuit boards. There is still much scope for miniaturizing flexible electronics further using photolithography, bringing the possibility of nanoscale, non-invasive, high-density flexible neural interfacing. This work explores the fabrication challenges of using photolithography and complementary techniques in a cleanroom for producing flexible electronic neural probes with nanometre-scale features. This article is part of the theme issue 'Advanced neurotechnologies: translating innovation for health and well-being'.

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“…Titanium dioxide was formed using a titanium tetraisopropoxide (TTIP) precursor (abcer GmbH, AB 113507) at 100 • C at a thickness of 15 and 30 nm. The deposition process is based on previous work (Potts et al, 2010;Westerhausen et al, 2020).…”

Section: Microelectrode Arraysmentioning

confidence: 99%

Low-Temperature Atomic Layer Deposited Oxide on Titanium Nitride Electrodes Enables Culture and Physiological Recording of Electrogenic Cells

et al. 2020

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The performance of electrode arrays insulated by low-temperature atomic layer deposited (ALD) titanium dioxide (TiO 2) or hafnium dioxide (HfO 2) for culture of electrogenic cells and for recording of extracellular action potentials is investigated. If successful, such insulation may be considered to increase the stability of future neural implants. Here, insulation of titanium nitride electrodes of microelectrode arrays (MEAs) was performed using ALD of nanometer-sized TiO 2 or hafnium oxide at low temperatures (100-200 • C). The electrode properties, impedance, and leakage current were measured and compared. Although electrode insulation using ALD oxides increased the electrode impedance, it did not prevent stable, physiological recordings of electrical activity from electrogenic cells (cardiomyocytes and neurons). The insulation quality, estimated from leakage current measurements, was less than 100 nA/cm 2 in a range of 3 V. Cardiomyocytes were successfully cultured and recorded after 5 days on the insulated MEAs with signal shapes similar to the recordings obtained using uncoated electrodes. Light-induced electrical activity of retinal ganglion cells was recorded using a complementary metal-oxide semiconductor-based MEA insulated with HfO 2 without driving the recording electrode into saturation. The presented results demonstrate that low-temperature ALD-deposited TiO 2 and hafnium oxide are biocompatible and biostable and enable physiological recordings. Our results indicate that nanometer-sized ALD insulation can be used to protect electrodes for long-term biological applications.

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Passivated electrode side walls by atomic layer deposition on flexible polyimide based samples

Cited by 7 publications

References 23 publications

A flexible protruding microelectrode array for neural interfacing in bioelectronic medicine

A flexible protruding microelectrode array for neural interfacing in bioelectronic medicine

Cleanroom strategies for micro- and nano-fabricating flexible implantable neural electronics

Low-Temperature Atomic Layer Deposited Oxide on Titanium Nitride Electrodes Enables Culture and Physiological Recording of Electrogenic Cells

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