Long-Term Stable Neural Interfaces with Nanoporous Graphene Electrodes and Hybrid Polyimide-Aluminium Oxide...

Area of Science:

• Biomaterials Science
• Neurotechnology
• Materials Engineering

Background:

• Graphene's unique properties offer potential for advanced neural interfaces.
• Long-term reliability of graphene neural interfaces is hindered by encapsulation instability in physiological conditions.
• Current encapsulation methods like ceramics lack compatibility with miniaturized implants.

Purpose of the Study:

• To develop and validate a chronically stable graphene-based neural interface.
• To address the challenge of thin-film encapsulation instability in physiological environments.
• To demonstrate the efficacy of a hybrid encapsulation strategy for enhanced device longevity.

Main Methods:

• Integration of nanoporous reduced graphene oxide (rGO) microelectrodes with a hybrid polyimide/atomic layer deposited (ALD) Al2O3 encapsulation.
• Validation of encapsulation robustness using flexible interdigitated electrodes (IDEs) under accelerated aging and electrical stress.
• Long-term soaking tests in phosphate buffer saline (PBS) at elevated temperatures (57°C) and continuous electrical stimulation.

Main Results:

• The hybrid encapsulation demonstrated exceptional stability, withstanding over 1.5 years of soaking in PBS at 57°C.
• Nanoporous rGO microelectrodes maintained structural integrity and electrochemical performance after 377 days in PBS at 57°C.
• The interfaces withstood 1 billion biphasic pulses at high charge density (1 mC cm⁻²) and hundreds of bending cycles without performance degradation.

Conclusions:

• A long-term stable graphene-based neural interface was successfully developed using nanoporous rGO electrodes and hybrid polyimide/Al2O3 encapsulation.
• This hybrid encapsulation strategy significantly enhances the reliability and durability of graphene neural interfaces.
• The demonstrated technology is a key advancement for chronic brain monitoring and neuromodulation applications.