Abstract
In this study, we report a flexible implantable 4-channel microelectrode probe coated with highly porous and robust nanocomposite of poly (3,4-ethylenedioxythiophene) (PEDOT) and carbon nanofiber (CNF) as a solid doping template for high-performance in vivo neuronal recording and stimulation. A simple yet well-controlled deposition strategy was developed via in situ electrochemical polymerization technique to create a porous network of PEDOT and CNFs on a flexible 4-channel gold microelectrode probe. Different morphological and electrochemical characterizations showed that they exhibit remarkable and superior electrochemical properties, yielding microelectrodes combining high surface area, low impedance (16.8 ± 2 MΩ µm2 at 1 kHz) and elevated charge injection capabilities (7.6 ± 1.3 mC/cm2) that exceed those of pure and composite PEDOT layers. In addition, the PEDOT-CNF composite electrode exhibited extended biphasic charge cycle endurance and excellent performance under accelerated lifetime testing, resulting in a negligible physical delamination and/or degradation for long periods of electrical stimulation. In vitro testing on mouse brain slices showed that they can record spontaneous oscillatory field potentials as well as single-unit action potentials and allow to safely deliver electrical stimulation for evoking field potentials. The combined superior electrical properties, durability and 3D microstructure topology of the PEDOT-CNF composite electrodes demonstrate outstanding potential for developing future neural surface interfacing applications.
Highlights
Neural electrodes provide the critical interface between the nervous system and electronics
We have developed a well-controlled and versatile surface modification method for preparing macroporous PEDOTCNFs microelectrodes on flexible implantable neural probes
We investigated by FIB and energy dispersive X-ray (EDX) the mechanism by which a macroporous nanostructure of PEDOT-CNF layer was created, where the conducting PEDOT polymer was covered uniformly and tightly around the oxidized carbon nanofibers as a solid doping template
Summary
Neural electrodes provide the critical interface between the nervous system and electronics. Welldefined anatomical regions from the brain can be the targets of implanted microelectrodes, enabling localized neuromodulation by either recording or delivering electrical signals at the level of individual neuron (Nicolelis et al, 2003; Spira and Hai 2013) Such capabilities have been critically important for supporting neuroscience research along with emerging clinical devices aimed at treating debilitating disorders, including deafness (Sparreboom et al, 2010), paralysis (Schultz and Kuiken 2011), blindness (Rizzo et al, 2003), Parkinson’s disease (Benabid 2003), epilepsy (Theodore and Fisher 2004) and other disorders (Mayberg et al, 2005). An ideal electrode should display a high storage capability to safely inject current pulses with minimal potential transients at the electrode/tissue interface, decreasing both electrode polarization and heat accumulation during stimulation (Merrill et al, 2005; Cogan 2008; Boehler et al, 2020)
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