Abstract
Neural interfaces are the parts of the neural prosthesis that are in contact with the target tissue. The mechanical, chemical, and electrical properties of these interfaces can be a major determinant of the life of the implant and the neural tissue for chronic and even acute integrations. In this work, we developed a fully inkjet-printed, flexible neural interface on a bioresorbable backbone capable of recording high-fidelity neural activity. We utilized room temperature fabrication processes that overcome the limitations of semiconductor fabrication techniques for processing low-melting point polymers while maintaining high spatial and single-cell recording resolution. The ∼8 μm-thick devices in this study were fabricated onto two flexible polymers: (a) polyimide (PI), a biocompatible polymer commonly used for neural interfaces, and (b) polycaprolactone (PCL), a bioresorbable polyester with outstanding mechanical properties. Electrodes for neural recording were built at 30, 50, 75, and 100 μm diameter using silver nanoparticles/(3,4-ethylenedioxytiophene)-poly(styrenesulfonate) (AgNPs/PEDOT:PSS), which through our process achieved the lowest impedance reported in the literature reaching ∼200 Ω at 1 kHz for a 50 μm electrode diameter. We further enhanced the electrochemical performance of AgNPs/PEDOT:PSS by an order of magnitude by incorporating exfoliated graphene into the electrodes. The biocompatibility of the fabricated devices and their ability to record single-unit activity were confirmed by in vitro tests on both rat PC12 cells and isolated neural rat retina, respectively.
Highlights
Neural interfaces play a major role in prosthetic intervention aimed at the treatment and management of neurological diseases.[1−3] These interfaces consist of the component of a neural prosthesis that is in intimate contact with target tissue and where signal transduction occurs for neural recording or modulation
We investigated the electrochemical performance of inkjet-printed PEDOT:PSS electrodes for both electrode diameter and electrode thickness
The present study demonstrated the fabrication of a single-cell resolution, high electrochemical performance flexible neural interface array on a bioresorbable backbone
Summary
Neural interfaces play a major role in prosthetic intervention aimed at the treatment and management of neurological diseases.[1−3] These interfaces consist of the component of a neural prosthesis that is in intimate contact with target tissue and where signal transduction occurs for neural recording or modulation. The complexity of acute or chronic integration of an electronic device with neural tissue (especially at the interface) has limited the life and efficiency of clinical prosthetic intervention This is due to several challenges including: tissue and implant damage caused by unwanted chemical reactions at the electrodes, damage due to invasive surgeries for device resection in the case of patients requiring postoperative monitoring,[2] and mechanical mismatch between the neural tissue and the implant inducing stress on the tissue.
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