A team led by Stephanie Lacour at the EPFL Neuro X Institute in Switzerland has developed a minimally invasive, soft robotic-inspired cortical electrode array that can be inserted through a small hole in the skull. The soft neurotechnology will be scaled by Neurosoft Bioelectronics, an EPFL spin-off from the Laboratory for Soft Bioelectronic Interfaces, that will lead its clinical translation.
The team – who specialize in compliant electrodes – was asked to create a large cortical electrode array that could be inserted through a small hole in the skull, deploying the device in a space that measures about 1 mm between the skull and the surface of the brain, all without damaging the brain.
“Minimally invasive neurotechnologies are essential approaches to offer efficient, patient-tailored therapies,” says Stéphanie Lacour, professor at EPFL Neuro X Institute. “We needed to design a miniaturized electrode array capable of folding, passing through a small hole in the skull and then deploying in a flat surface resting over the cortex. We then combined concepts from soft bioelectronics and soft robotics.”
The cortical electrode array that they designed features six spiraled arms that maximize surface area and thus the number of electrodes in contact with the cortex. Prior to deployment, the arms are folded up inside a cylindrical tube, which fits through a hole 2 cm in diameter, but when deployed, extends across a surface that is 4 cm in diameter. Using an everting actuation mechanism, each arm can then individually be deployed on top of highly sensitive brain tissue. The deployable electrode array has been successfully tested in a mini-pig.
“The beauty of the eversion mechanism is that we can deploy an arbitrary size of electrode with a constant and minimal compression on the brain,” says Suhko Song, lead author of the study. “The soft robotics community has been very much interested in this eversion mechanism because it has been bio-inspired. This eversion mechanism can emulate the growth of tree roots, and there are no limitations in terms of how much tree roots can grow.”