Impedance spectroscopy and nanoindentation of conducting poly(3,4-ethylenedioxythiophene) coatings on microfabricated neural prosthetic devices
Junyan Yanga1 p1 and David C. Martina2 c1
a1 Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136
a2 Departments of Materials Science and Engineering, and Biomedical Engineering, and Macromolecular Science and Engineering Center, University of Michigan, Ann Arbor, Michigan 48109-2136
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Vertically aligned carbon nanofibers (VACNFs) hold significant promise as a new material interface for electroanalytical and electrophysiological coupling with neuronal tissue. VACNFs may be readily integrated into microfabricated devices to provide discrete, individually addressed sensing and/or stimulating electrodes at active probing dimensions approaching <100 nm2. In addition to providing predictable electrochemical response, the morphological characteristics and chemical composition of VACNFs contribute to a biocompatible interface. They may also be tailored using a variety of post synthesis surface modifications to promote improved biocompatibility, tissue integration, or to provide electroanalytical sensitivity to specific molecular species. Flexible films of VACNFs, which preserve the high aspect ratio morphology of these electrodes as well as their spatial distribution, can be mated with high density microelectronics, such as CMOS integrated circuits, to form complex monitoring and stimulating systems enabling both electroanalytical and electrophysiological assays. We report recent progress in the synthesis of VACNF arrays and their integration into systems for neuroscience applications including the development of flexible films of electroactive VACNF arrays and their incorporation with low-temperature CMOS substrates. Experimental results will be presented demonstrating both action potential monitoring and neurotransmitter detection using VACNF systems in neuronally-differentiated cell culture. In addition, VACNF performance for electrophysiological stimulation and recording from organotypic hippocampal slice cultures will be compared to data obtained using commercially available microelectrode arrays. Future systems based on VACNF arrays and integrated circuits may provide new strategies for highly miniaturized, programmable, and efficient multi-mode neuroprosthetic interfaces.-Timothy McKnight
a2 Departments of Materials Science and Engineering, and Biomedical Engineering, and Macromolecular Science and Engineering Center, University of Michigan, Ann Arbor, Michigan 48109-2136
Abstract
The electrical and mechanical properties of conducting polymer poly(3,4-ethylenedioxythiophene) coatings on microfabricated neural probes have been evaluated by electrochemical impedance spectroscopy and nanoindentation techniques. Our results reveal that for poly(3,4-ethylenedioxythiophene) coatings, the minimum impedance correlates well with the mechanical properties. The lowest impedance films are also those that are the softest. This is consistent with microstructural observations by atomic force microscopy and scanning electron microscopy showing an increase in the effective surface area (“fuzziness”) of the coatings. The presence of these conducting polymer coatings provides an intermediate step along the interface between the devices and brain tissue. This information provides clues for the design of strategies for improving the long-term performance of these electrodes in vivo.(2)
Vertically aligned carbon nanofibers (VACNFs) hold significant promise as a new material interface for electroanalytical and electrophysiological coupling with neuronal tissue. VACNFs may be readily integrated into microfabricated devices to provide discrete, individually addressed sensing and/or stimulating electrodes at active probing dimensions approaching <100 nm2. In addition to providing predictable electrochemical response, the morphological characteristics and chemical composition of VACNFs contribute to a biocompatible interface. They may also be tailored using a variety of post synthesis surface modifications to promote improved biocompatibility, tissue integration, or to provide electroanalytical sensitivity to specific molecular species. Flexible films of VACNFs, which preserve the high aspect ratio morphology of these electrodes as well as their spatial distribution, can be mated with high density microelectronics, such as CMOS integrated circuits, to form complex monitoring and stimulating systems enabling both electroanalytical and electrophysiological assays. We report recent progress in the synthesis of VACNF arrays and their integration into systems for neuroscience applications including the development of flexible films of electroactive VACNF arrays and their incorporation with low-temperature CMOS substrates. Experimental results will be presented demonstrating both action potential monitoring and neurotransmitter detection using VACNF systems in neuronally-differentiated cell culture. In addition, VACNF performance for electrophysiological stimulation and recording from organotypic hippocampal slice cultures will be compared to data obtained using commercially available microelectrode arrays. Future systems based on VACNF arrays and integrated circuits may provide new strategies for highly miniaturized, programmable, and efficient multi-mode neuroprosthetic interfaces.-Timothy McKnight
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