The brain is a sea of electrical impulses and currents traveling along axons in order to transmit and receive information in the form of electrical charges. The brain has nearly 100 billion neurons, each possessing axons that are continuously communicating with each other through a series of electrical impulses (known as action potentials). This means that there are 100 billion different “pathways” in our brain, and if one single pathway is damaged or not functioning properly, the entire body may suffer extreme physiological effects.1
Biomedical Engineers have attempted to map the neuronal activity of the brain by placing long, thin, micro-electrodes in different regions of the brain to record the electrical activity of the brain produced by the action potentials propagating across axons. Most devices for neuronal assessment are composed of rigid metals, which make it easier for these materials to navigate and penetrate through the dense regions of the brain.2 Although, a drawback in using rigid metals is that they do not possess desirable mechanical properties such as Young’s modulus, bending stiffness, or size for complete biocompatibility within the brain.3 An alternate approach that is being developed by Neuralink Inc. is to use thin, flexible, multi-electrode polymer probes that range from 5-50 um in width.4 The increased ductility of the polymer compared to the rigid metal and the smaller size of the polymer probes make them substantially more biocompatible for the aggressive environment that is the human brain. To optimize the insertion method of very flexible thin probes, Neuralink is developing its own surgical robot. The three components of the neuronal activity mapping system are:
1.) Thin, flexible polymer probes
2.) Neurosurgical robot
3.) Custom high-density electronics (including printed circuit boards)
The polymer used for these probes is Polyimide, which encapsulates a gold thin film.5 Polyimides are polymers that were first developed by the DuPont company and exhibit an interesting combination of desirable material properties for useful biocompatible applications:
-Exceptional thermal stability (at T > 500C)
-Chemical resistance
-Dielectric properties
-Low coefficient of thermal expansion.
This combination of properties potentially translates to a useful biocompatible material that can propagate and record action potential signals in the brain due to its inherent dielectric ability as well as its ability to resist corrosion or thermal expansion in the incredibly dynamic and aggressive environment of the brain. Biosensors as neural implants have extensive research yet to be performed before they can be practically and commercially marketed for normal clinical use. We at EMMA are not only excited to see what the future holds, but we’re excited to be making it happen.
Are you struggling to get your device or drug FDA approved? Give EMMA International a call today at 248-997-4497 to learn which regulatory pathway is right for your product. We specialize in full-circle consulting to help get your product approved and out to market in the most efficient way possible.
- Herculano-Houzel, S. (2009). The human brain in numbers: a linearly scaled-up primate brain. Frontiers in Human Neuroscience, 3. https://doi.org/10.3389/neuro.09.031.2009
- Ordonez, J. S., Boehler, C., Schuettler, M., & Stieglitz, T. (2012). Improved polyimide thin-film electrodes for neural implants. 2012 Annual International Conference of the IEEE Engineering in Medicine and Biology Society. https://doi.org/10.1109/embc.2012.6347149
- Ceyssens, F., & Puers, R. (2015). Insulation lifetime improvement of polyimide thin film neural implants. Journal of Neural Engineering, 12(5), 054001. https://doi.org/10.1088/1741-2560/12/5/054001
- Musk, E. (2019). An integrated brain-machine interface platform with thousands of channels. https://doi.org/10.1101/703801
- Sohal, H. S., Vassilevski, K., Jackson, A., Baker, S. N., & O’Neill, A. (2016). Design and Microfabrication Considerations for Reliable Flexible Intracortical Implants. Frontiers in Mechanical Engineering, 2. https://doi.org/10.3389/fmech.2016.00005
