Soft-bodied brain electrode array squeezes through a hole half its size

In the treatment of epilepsy and other neurological disorders, doctors will sometimes implant arrays of stimulating electrodes on the surface of a patient’s brain. A new soft robotic system allows those electrodes to be placed far less invasively than ever before.

The problem with implanting a whole group of linked electrodes lies in the fact that a relatively large portion of the skull has to be removed (and then replaced) in the process. Needless to say, it would be much better if just a small hole could suffice.

With that challenge in mind, scientists at Switzerland’s EPFL research institute designed an “inflatable” electrode array made of a soft biocompatible elastomer, with six spiral-shaped arms that spread out like the petals of a twisted flower. Each arm has multiple gold electrodes on its underside.

Initially, the deflated device is folded up inside-out within a cylindrical tube. The end of that tube is then inserted into the 1-mm space between the brain and the skull, through a 2-cm (0.8-inch)-wide hole in the skull. An innocuous liquid is then pumped into the array, causing each of its arms to sequentially inflate and gently pop into shape inside the skull.

The array is deployed inside a model skull
The array is deployed inside a model skull


When the process is complete, the flower-shaped array covers a 4-cm (1.6-in) wide area of the brain’s cortex, even though it went through a hole just half that size. And because the arms of the array turn right-side-out as they’re inflated, the electrodes on their underside make full contact with the brain tissue.

The technology has already been successfully tested on miniature pigs, and is now being commercialized by EPFL spinoff company Neurosoft Bioelectronics. As the device is developed further, the sizes of the hole in the skull and the deployed electrode array will likely decrease and increase, respectively.

A paper on the study, which is being led by Prof. Stéphanie Lacour and robotics researcher Sukho Song, was recently published in the journal Science Robotics. The system is demonstrated in the video below.

Deployable electrodes for minimally invasive craniosurgery

Source: EPFL

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