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Failure Reason of PI Test Samples of Neural Implants
Jürgen Guljakow1, Walter Lang1
1Institute for Microsensors, Actuators, Systems (IMSAS), University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany.
Sensors (Basel, Switzerland)
|February 11, 2023
Summary
Accelerated lifetime testing of neural implant materials revealed delamination as a common failure mode. However, temperature-dependent voltage fluctuations suggest limitations in accelerated testing for predicting real-world neural implant performance.
Area of Science:
- Biomaterials Science
- Materials Engineering
- Neurotechnology
Background:
- Neural implants require robust materials to withstand physiological environments.
- Polyimide-encapsulated structures are used in neural implants.
- Understanding material degradation is crucial for implant longevity and safety.
Purpose of the Study:
- To assess the damage and failure mechanisms of simulated neural implant samples in Ringer's solution.
- To compare the effects of different temperatures (37°C and 57°C) on material degradation.
- To evaluate the correlation between electrical measurements and physical damage.
Main Methods:
- Simulated neural implant samples with interdigitated gold structures were immersed in Ringer's solution.
- Accelerated lifetime testing was conducted at 37°C and 57°C with applied voltage monitoring.
- Failure was indicated by a sudden voltage rise, signifying liquid ingress.
- Post-failure analysis included microscopic examination for delamination.
Main Results:
- Delamination was observed in nearly all failed samples, though the extent varied.
- No direct correlation was found between post-failure voltage and the area of delamination.
- At 37°C, voltage remained stable post-delamination, while pin-holes caused fluctuations.
- Higher temperatures (57°C) showed more voltage fluctuations, hinting at different failure origins.
Conclusions:
- Delamination is a primary failure mode in these simulated neural implant structures.
- Accelerated lifetime testing at elevated temperatures may not accurately reflect failure mechanisms at physiological temperatures.
- Voltage fluctuation patterns provide insights into failure modes, suggesting limitations in accelerated testing applicability.
