February 20, 2017

Ultraflexible Probes Have Implications for Neuroprosthetics

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This rendering of the ultraflexible probe in neural tissue gives viewers a sense of the deviceís tiny size and footprint in the brain. Rendering courtesy of Science Advances.

Engineering researchers at The University of Texas at Austin (UT Austin) have designed ultraflexible, nanoelectronic-thread brain probes that can achieve more reliable long-term neural recording than existing probes and donít elicit scar formation when implanted. There is a growing interest in developing long-term tracking of individual neurons for neural interface applications, such as extracting neural-control signals for people with amputations to control high-performance prostheses. It also opens possibilities to follow the progression of neurovascular and neurodegenerative diseases such as stroke, Parkinsonís, and Alzheimerís. The researchers describe their findings in a research article published on February 15 in Science Advances.

One of the problems with conventional probes is that their size and mechanical stiffness frequently cause damage around the tissue they encompass. Additionally, while it is possible for the conventional electrodes to record brain activity for months, they often provide unreliable and degrading recordings. It is also challenging for conventional electrodes to electrophysiologically track individual neurons for more than a few days.

In contrast, the UT Austin teamís electrodes have mechanical compliances approaching that of brain tissue and are more than 1,000 times more flexible than other neural probes. This ultraflexibility leads to an improved ability to reliably record and track the electrical activity of individual neurons for long periods of time, and they comply with the microscale movements of tissue and still stay in place. The probeís size also drastically reduces the tissue displacement, so the brain interface is more stable, and the readings are more reliable for longer periods of time. To the researchersí knowledge, the UT Austin probeówhich has a cross-section that is only a fraction of that of a neuron or blood capillaryóis the smallest among all neural probes.

In experiments in mouse models, the researchers found that the probeís flexibility and size prevented the agitation of glial cells, which is the normal biological reaction to a foreign body and leads to scarring and neuronal loss.

Editorís note: This story was adapted from materials provided by UT Austin.

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