The problem
Brain electrodes can work for years. Can a shorter laboratory test predict how a new design will fail in the brain?[1]
A brain-recording probe may lose useful signals because its metal, insulation or surrounding tissue changes. Which accelerated test predicts those failures during years of implantation? A 2015 screening experiment combined heat and reactive chemicals: polyimide insulation peeled away and tungsten wires corroded. Measuring electrical impedance at one frequency could miss substantial damage.[1] [2]
Scope
Accelerated qualification of chronic cortical probes that reproduces relevant physiological failure mechanisms and predicts in-vivo reliability across materials and architectures.
What remains open
A faster test must reproduce the kinds of damage that happen in the brain.[1]
Why it matters
Predictive tests could help identify durable designs sooner.[1]
Definitions
2 terms
accelerated test
A laboratory test that uses stronger stresses to produce damage sooner. Predicting implanted life requires checking that the accelerated damage follows relevant failure mechanisms.[1] [2]
electrical impedance
How an electrode resists and delays an alternating electrical signal. Its value depends on frequency and can change for several different reasons.[2]
Sources
- Material and design strategies for chronically-implantable neural probes
Notes on Material and design strategies for chronically-implantable neural probes
Outlook calls for accelerated tests matching brain microenvironments despite recordings lasting years.
- Rapid evaluation of the durability of cortical neural implants using accelerated aging with reactive oxygen species
Notes on Rapid evaluation of the durability of cortical neural implants using accelerated aging with reactive oxygen species
Original harsh-environment test distinguishes thermal and oxidative damage; single-frequency impedance was an unreliable marker.