Chew, D. J. | Search bioRxiv

bioRxiv2019

Printable microscale interfaces for long-term peripheral nerve mapping and precision control

The nascent field of bioelectronic medicine seeks to decode and modulate peripheral nervous system signals to obtain therapeutic control of targeted end organs and effectors. Current approaches rely heavily on electrode-based devices, but size scalability, material and microfabrication challenges, limited surgical accessibility, and the biomechanically dynamic implantation environment are significant impediments to developing and deploying advanced peripheral interfacing technologies. Here, we present a microscale implantable device - the nanoclip - for chronic interfacing with fine peripheral nerves in small animal models that begins to meet these constraints. We demonstrate the capability to make stable, high-resolution recordings of behaviorally-linked nerve activity over multi-week timescales. In addition, we show that multi-channel, current-steering-based stimulation can achieve a high degree of functionally-relevant modulatory specificity within the small scale of the device. These results highlight the potential of new microscale design and fabrication techniques for the realization of viable implantable devices for long-term peripheral interfacing.

neuroscience↗

bioRxiv2017

Carbon Fiber On Polyimide Ultra-Microelectrodes

Most preparations for making neural recordings degrade over time and eventually fail due to insertion trauma and reactive tissue response. The magnitudes of these responses are thought to be related to the electrode size (specifically, the cross-sectional area) and the relative stiffness of the electrode material. Carbon fiber ultramicroelectrodes have a much smaller cross-section than traditional electrodes and thus may enable improved longevity of neural recordings in the central and peripheral nervous systems. Only two carbon fiber array designs have been described previously, each with limited channel densities due to limitations of the fabrication processes or interconnect strategies. Here, we describe a method for assembling carbon fiber electrodes on a flexible polyimide substrate that will facilitate the construction of high-density recording and stimulating arrays for acute use in peripheral nerves. Fibers were aligned using an alignment tool that was 3D-printed with sub-micron resolution using direct laser writing. Indium deposition on the carbon fibers provided a robust and reliable method of electrical connection to the polyimide traces. Spontaneous action potentials and stimulation-evoked compound responses with SNR > 10 and > 120, respectively, were recorded from a small (125 m) peripheral nerve. We also improved the typically poor charge injection capacity of small diameter carbon fibers can be improved by electrodepositing 100 nm thick iridium oxide films, making the carbon fiber arrays suitable for electrical stimulation as well as recording.

neuroscience↗