Safety margin for strain at the electrode-tissue interface

Is the 5% strain threshold truly the safety limit before brain tissue damage occurs?

This critical question was investigated by Sharbatian and colleagues from the Laboratory for Biomedical Microtechnology (IMTEK) and BrainLinks-BrainTools. Their research, featured on the back cover of the Journal of Advanced MaterialS Interfaces, sheds new light on this issue.

In their study, the team employed a numerical approach to assess how neural electrodes and brain movements affect the strain in brain tissue. Building on the neural probe design known as PIXI [Vomero et al. Biomaterials, 2022], Sharbatian et al. examined various types of brain movements—lateral, diagonal, vertical, and torque—using three different brain physics models: linear elastic, viscoelastic, and hyperelastic.

Their findings challenge the established 5% strain limit for biological tissue and provide insights into the strengths and weaknesses of each simulation model used. The research also highlights the potential to use existing post-implantation immunohistological data to validate the simulation results. This represents a promising approach to minimize sources of error in the early phase of neural interface design, thereby reducing the need for unnecessary animal testing.

The study is freely available here:

https://advanced.onlinelibrary.wiley.com/doi/10.1002/admi.202401001