A high-density, stretchable, 32-electrode grid for neural recording and neurological disorder treatment

A potential Neuralink device? (see SXSW video)
March 12, 2018

Photo of a new soft, elastic, high-density 32-electrode grid for long-term, stable neural recording and treatment of neurological disorders. It’s based on a novel biocompatible, elastic material that retains high electrical conductivity, even when stretched to double its original length. The 32 electrodes shown here are each 50 micrometers wide and located at a distance of 200 micrometers from each other. The fabrication procedure allows 32 electrodes to be placed onto a very small surface. The electrode grid is 3.2 millimeters wide and 80 micrometers thick. (credit: Thor Balkhed)

An international team has developed a soft, elastic, high-density stretchable electrode grid for long-term, stable neural recording, and diagnosis and treatment of neurological disorders, such as epilepsy.

Researchers at Linköping University and ETH Zürich developed the biocompatible, soft-material composite, which avoids the usual damage and inflammation to neurons from rigid metallic electrodes and components.

Titanium-oxide nanowires coated with conductive gold nanoparticles, made stretchable by embedding in PDMS, a non-toxic, silicon-based organic polymer (scale bar: 500 nanometers) (credit: Klas Tybrand et al./Adv. Mater.)

The material consists of gold coated titanium dioxide nanowires embedded into silicone rubber. It has the highest electrode density of any stretchable electrode grid to date, according to the researchers. As soft as human tissue, it retains high electrical conductivity over time — even when stretched to double its original length.

Researchers at New York University and Columbia University implanted the electrode grid over the somatosensory cortex of freely moving rats, and were able to collect high-quality neural signals for three months. The flexible and stretchable quality also made it possible to minimize the size of the cranial hole required for placement.

The stretchability of the electrode grid allows it to establish conformal contact around curved surfaces. (credit: Klas Tybrand et al./Adv. Mater.)

“We have developed a process to manufacture small electrodes that also preserves the biocompatibility of the materials. The process uses very little material, and this means that we can work with a relatively expensive material such as gold, without the cost becoming prohibitive,” says Klas Tybrandt, Klas Tybrandt, principal investigator at the Laboratory of Organic Electronics at Linköping University and lead author of a paper on the breakthrough published in Advanced Materials.

Future applications could include brain-machine interfaces and neuroprostheses.


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Abstract of High-Density Stretchable Electrode Grids for Chronic Neural Recording

Electrical interfacing with neural tissue is key to advancing diagnosis and therapies for neurological disorders, as well as providing detailed information about neural signals. A challenge for creating long-term stable interfaces between electronics and neural tissue is the huge mechanical mismatch between the systems. So far, materials and fabrication processes have restricted the development of soft electrode grids able to combine high performance, long-term stability, and high electrode density, aspects all essential for neural interfacing. Here, this challenge is addressed by developing a soft, high-density, stretchable electrode grid based on an inert, high-performance composite material comprising gold-coated titanium dioxide nanowires embedded in a silicone matrix. The developed grid can resolve high spatiotemporal neural signals from the surface of the cortex in freely moving rats with stable neural recording quality and preserved electrode signal coherence during 3 months of implantation. Due to its flexible and stretchable nature, it is possible to minimize the size of the craniotomy required for placement, further reducing the level of invasiveness. The material and device technology presented herein have potential for a wide range of emerging biomedical applications.

References:

  • Klas Tybrandt, Dion Khodagholy, Bernd Dielacher, Flurin Stauffer, Aline F. Renz, György Buzsáki, János Vörös. High-Density Stretchable Electrode Grids for Chronic Neural Recording. Advanced Materials, 2018; 1706520 DOI: 10.1002/adma.201706520