Robust penetrating microelectrodes for neural interfaces realized by titanium micromachining

Neural prosthetic interfaces based upon penetrating microelectrode devices have broadened our understanding of the brain and have shown promise for restoring neurological functions lost to disease, stroke, or injury. However, the eventual viability of such devices for use in the treatment of neurological dysfunction may be ultimately constrained by the intrinsic brittleness of silicon, the material most commonly used for manufacture of penetrating microelectrodes. This brittleness creates predisposition for catastrophic fracture, which may adversely affect the reliability and safety of such devices, due to potential for fragmentation within the brain. Herein, we report the development of titanium-based penetrating microelectrodes that seek to address this potential future limitation. Titanium provides advantage relative to silicon due to its superior fracture toughness, which affords potential for creation of robust devices that are resistant to catastrophic failure. Realization of these devices is enabled by recently developed techniques which provide opportunity for fabrication of high-aspect-ratio micromechanical structures in bulk titanium substrates. Details are presented regarding the design, fabrication, mechanical testing, in vitro functional characterization, and preliminary in vivo testing of devices intended for acute recording in rat auditory cortex and thalamus, both independently and simultaneously

Flexible Electrode for Implantable Neural Devices

The function of neural electrodes is to interface with the neural system for both sensory and actuation purposes. One of the major challenges in neural devices is to achieve a precise and reliable neuron–electrode interface (NEI). Advances in microfabrication technologies create the possibility to increase the number and reduce the size of electrode sites which can improve the spatial resolution of the NEI. Alternatively, replacing the substrate material of the microfabricated neural electrode from the rigid silicon to the flexible polymer can minimize the stiffness mismatch between electrodes and neural tissue, thus potentially improving the reliability of NEI. In this chapter, we provide an overview of the recent development in microfabricated polymeric neural electrodes. At first, we give a summary of material properties and fabrication processes for some polymers commonly used in the neural electrode application. Then, we review various designs of polymeric neural electrodes in the context of their specific applications. Finally, challenges and corresponding strategies in the development and practicability of polymeric neural electrodes are discussed. © Springer Science+Business Media New York 2014.1