Author ORCID Identifier

https://orcid.org/0009-0009-8310-7244

Semester

Summer

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

Stephen Cain

Committee Member

Loren Rieth

Committee Member

Xueyan Song

Abstract

Durable dielectric encapsulation is crucial for the long-term function of implantable neural electrodes; however, the reliability of curved, thermoformed coatings remains underexplored. This study addresses that gap by comparing planar (non-thermoformed) and thermoformed interdigitated neural electrodes (IDEs) encapsulated in Polyimide-2611. Both device types underwent accelerated in vitro aging in phosphate‑buffered saline (PBS) at 67 °C for approximately 91 days, simulating two years of physiological exposure. Post-accelerated aging evaluation included electrochemical impedance spectroscopy (EIS) from 0.1 Hz to 100 kHz to monitor moisture‑induced leakage, and high‑voltage breakdown testing under saline immersion to assess dielectric strength. After aging, all electrodes maintained impedance magnitudes above 10⁹ Ω at 0.1 Hz, 10⁶ Ω at 1 kHz, and 10⁴ Ω at 100 kHz. Initial breakdown voltages for Channel 1 averaged 3.4 kV for planar electrodes and 3.2 kV for thermoformed electrodes, indicating comparable insulation performance. Failure‑mode analysis localized leaks to the integration procedure at the solder pad interface rather than to the bulk polyimide film. These results demonstrate that thermoforming enables anatomically conformal electrode geometries without compromising long‑term encapsulation integrity, supporting the development of flexible neural interfaces.

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