Nanowerk is reporting on recent research from Japan’s National Institute of Advanced Industrial Science and Technology and Toyohashi University of Technology to build a new type of nanotech-based peripheral nerve interface electrodes:
Neural interfaces used for such purposes as electroencephalography are noninvasive, but suffer from relatively poor spatial and temporal resolution of signals. The type of neural interface that uses electrodes inserted in the brain and measures neuronal activities is more effective, but might leave behind irreversible lesions in the cerebrum because of the need to implant electrodes in brain tissue. Other problems with this type of neural interface include the difficulty of obtaining information about individual organs.
Believing that an effective solution to these problems lies in designing a neural interface that attaches not to the cerebrum but to peripheral nerves, Hidekazu Kaneko from the Institute for Human Science and Biomedical Engineering at AIST and his team have been working with Makoto Ishida’s Integrated Circuit Group at Toyohashi University of Technology to develop an electrode for a peripheral nerve interface.
According to Kaneko, the electrode under development should have the capability of simultaneously measuring the action potentials of individual nerve fibers in a peripheral nerve bundle. Earlier proposals for measuring peripheral nerve activity were based on the use of sieve electrodes, needle point holder-shaped electrodes, and cuff electrodes; but these and other attempts have been unable to meet the requirement for low invasive measurement that is also able to distinguish the activity of individual nerve fibers.
Applying the selective Vapor-Liquid-Solid (VLS) growth technique to electrode development, the team has succeeded in forming a structure like that shown in the electron microscope photograph [see top image].
The resulting electrode combines an unprecedented low-invasive design with ease of incorporation on an integrated circuit substrate. Moreover, using an array of metal microelectrodes having similar recording surface area as this electrode, the researchers have confirmed the ability to take localized measurements of evoked action potentials in single peripheral nerve fibers for all-or-nothing responses.
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Image: An electron microscope photograph of the microprobe electrode array under development (left). Conventional microelectrodes are thick, typically from several tens to a hundred micrometers in diameter. The microprobes shown here are extremely fine with a diameter of only 2 micrometers, for low-invasive use. Moreover, these microprobes can be grown on a semiconductor substrate (right).