Frontiers of Engineering Reports on Leading-Edge Engineering from the 2013 Symposium (2014) / Chapter Skim
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Biocompatible Materials for Optoelectronic Neural Probes: Challenges and Opportunities--Polina Anikeeva
Biocompatible Materials for Optoelectronic Neural Probes: Challenges and Opportunities--Polina Anikeeva
Pages 141-156
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. Flexible organic and hybrid electronics offers a compelling solution to the elastic and surface chemistry mismatch between neural probes and neural tissues, while enabling novel approaches for neural interrogation.
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I focus here on penetrating neural recording devices, designed to interface with individual cells in a particular region of the nervous system. As with neural recording, neural stimulation offers varying degrees of precision and invasiveness.
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Thus, optical stimulation technologies face materials design and biocompatibility challenges similar to those of tissue-penetrating neural recording and stimulation electrodes. Reliability Challenges of Implantable Neural Probes Neural recording and stimulation devices have traditionally been fabricated out of hard materials with elastic moduli (Young's modulus E~10s–100s GPa 1)
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(A) Silicon multielectrode array (reprinted with permission from Blackrock Microsystems)
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Combining traditional metal and semiconductor technologies with flexible substrates provides a first transitional step toward stealthy bioinspired neural probes. Over the past decade polymer substrates have been used as a backing for metal and silicon-based neural recording electrodes.
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(B) Microprinted o ptoelectronic device on a polyimide substrate incorporating a gold electrode, a gallium nitride–based light-emitting diode, a silicon photo etector, d and a resistor for temperature monitoring.
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. Surface Modification and Encapsulation of Neural Probes Because materials interfaces between devices and neural tissues play a critical role in both tissue response and the quality of neural recording, surface engineering is an important aspect of neural probe design.
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to solve the elastic mismatch of neural recording devices while reducing the overall electrode impedance and thus increasing SNR. In parallel, Capadona and Tyler have applied biologically inspired design principles to create polymer composites with controllable elastic properties that mimic sea cucumber dermis (Capadona et al.
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From page 149... ...
Furthermore, these methods currently do not allow for integration of optical elements, which are essential for neural stimulation applications. Although well-developed lithographic methods allow for integration of multiple functional elements, they are limited by the flat substrate geometry, which is not ideal for applications in deep brain regions.
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While mature semiconductor technologies provided initial promise for neural probe design, recent tissue engineering studies illustrate the need for alternative biocompatible materials platforms. In this article I have reviewed the challenges of established neural probe technologies and the opportunities of flexible organic and hybrid materials platforms for improvements in the biocompatibility and longevity of these sensors.
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(D) Optically evoked action potentials recorded with a FINP in the medial prefrontal cortex of a transgenic Thy1-ChR2-YFP mouse e xpressing ChR2 in a broad neuronal population.
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2011. Flexible, all-polymer microelectrode arrays for the capture of cardiac and neuronal signals.
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2010b. Conducting polymers on hydrogel coated neural electrode provide sensitive neural recordings in auditory cortex.
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(PEDOT) polymer coatings facilitate smaller neural recording electrodes.
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2011. Flexible, foldable, actively multiplexed, high density electrode array for mapping brain activity in vivo.
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