2023-05-19 16:30:00
EPFL scientists have developed a deployable array of electrodes over a relatively large area of the cerebral cortex, through a small hole drilled in the skull. The technology might provide a minimally invasive solution for epileptic patients.
Stéphanie Lacour specializes in the development of flexible electrodes, which adapt to body movements and connect to the nervous system more reliably. Basically, his work is interdisciplinary.
When a neurosurgeon asked his team to develop electrodes that were as minimally invasive as possible, insertable into a human skull, they came up with an elegant solution. The system takes advantage of its expertise in flexible electrodes and is inspired by soft robotics. The results are published in Science Robotics.
The challenge ? This involved inserting a large mesh of cortical electrodes through a small hole drilled in the skull. You have to deploy the device in the space of regarding a millimeter between the skull and the surface of the brain — without damaging the latter.
«Minimally invasive neurotechnologies are crucial approaches to delivering personalized and effective therapies, explains Stéphanie Lacour, professor at EPFL’s Neuro X Institute. We had to develop a miniaturized array of electrodes, able to bend, pass through a small hole before unfolding on a flat surface above the cortex. We have combined concepts from robotics and soft bioelectronics.»
Every aspect of this new electrode — from the spiral shape of the arms to their extension over fragile brain tissue — called upon the inventiveness of engineers.
Their first prototype consists of an array of electrodes that passes through a hole with a diameter of two centimeters but which, when unfolded, extends over a diameter of four centimeters. It has six spiral arms that maximize the area occupied by the electrode array and, therefore, the number of electrodes in contact with the cortex. Straight arms would result in uneven distribution and less surface contact with the brain.
Like a kind of spiral butterfly, encased in its chrysalis before metamorphosis, the electrode array — complete with its spiral arms — is neatly folded into a cylindrical tube — the applicator — ready to unfurl through a small hole in the skull.
Thanks to an actuation mechanism called ” annual versioninspired by flexible robotics, the spiral arms unfold one following the other above fragile brain tissue. “The beauty of the eversion mechanism is that we can deploy an electrode of arbitrary size while maintaining both constant and minimal compression on the brain,” says Sukho Song, first author of the study. “The soft robotics community has shown a lot of interest in this eversion mechanism, because it is bio-inspired. It emulates the growth of tree roots, which knows no bounds.”
The electrode array looks like a rubber glove. Flexible electrodes are distributed on each side of the spiral fingers. The glove is turned over on itself and folded in the applicator cylinder. During the unfolding above the brain, a liquid is injected into each arm, one following the other, and turns them to the correct side.
The electrodes are distributed by evaporation of flexible gold on an ultra-malleable substrate of elastomeric material.
For now, the device has been successfully tested on a dwarf pig. Neurosoft Bioelectronics, a spin-off from EPFL’s Soft Bioelectronic Interfaces Laboratory, will prepare this soft neurotechnology for transfer to clinical applications. The spin-off recently received 2.5 million francs, a “Swiss Accelerator” by Innosuisse.
Author: Hillary Sanctuary
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