TABLE 1.
Commonly used materials and carbon-based microfibers for neural stimulation and recording.
| Name | Dimension | Mechanical properties | Electrochemical properties | Biological performances | References | |||||||
| Electrode shank size (μm) | Electrode site geometric surface area (μm2) | Young’s moduls (GPa) | Flexural rigidity (N.m2) or other | CIC (mC/cm2) | CSC (mC/cm2) | Water Window (V) | Impedance at 1 kHz (kΩ) | Stimulation | Recording | |||
| Silicon- based MEA | Utah array (Electrode Materials: Pt or iridium oxide) | tip diameter: 25.4; base diameter: 80 | 2,000 | 165 | — | — | ∼36 (Iro) | −0.6–0.8 (IrO) | 50–60 | — | In vivo acute and chronic (5.75 years) recording in motor or premotor cortex in Rhesus macaques of monkeys | Barrese et al., 2013; Black et al., 2018; Choi et al., 2018 |
| NeuroNexus probe (Electrode Material: SIROF) | thickness: 15; width: 123 | 1,845 | 165 | 5.7 × 10–10 | 5.2 | 19.4 ± 2.4 | −0.6–0.8 | 88.5 | — | In vivo acute recording in rat motor cortex from SU | Deku et al., 2018a | |
| Metal wires | tungsten | Cylinder diameter: 50 | ∼2,300 | 390 | 1.2 × 10–7 | — | — | — | 40–150 | — | In vivo chronic recording in rat cortex and hippocampus for 4 months | Ward et al., 2009; Sankar et al., 2014; Shuang et al., 2020 |
| platinum | Cylinder diameter: 15 | 7,850 | 47 | — | 0.2 | 1.2 | −0.6–0.8 | 18 | — | In vivo acute recording of LFP in rat striatum | Apollo et al., 2015; Wei et al., 2015; Wang et al., 2019 | |
| platinum/iridium | Cylinder diameter: 15 | 78.5 | 233 | (1.23 ± 0.64) × 10–10 | 0.13 | 8 | −0.6–0.8 | 200 ± 27 | — | Ex vivo recording in rat retina; in vivo acute recording in deep cortical and subcortical regions in mice; in vivo chronic recording in motor cortex and striatum of awake moving mice for 14 days. | Venkatraman et al., 2011; Zheng, 2017; Obaid et al., 2020 | |
| Carbon-based fibers | bare CF | Cylinder diameter: 5 or 7 | 38 or 58.1 | 234 | 2.7 × 10–11 | 0.105 ± 0.067 | — | −0.6–0.4 | hundreds of KΩ | — | In vivo acute recording in rat motor cortex | Kozai et al., 2012; Massey et al., 2019; Hejazi et al., 2020a |
| bare CF | Cylinder diameter: 4.5 | — | 380 | — | — | — | — | median = 1,000 | — | In vivo chronic recording in zebra finches for up to 107 days | Guitchounts et al., 2013 | |
| PEDOT:PSS-co-MA coated CF | — | 1076.47 or 5472.47 | — | — | 96–192 | — | −0.9–0.4 | 5 | Ex vivo stimulation in rat at the cervical spinal cord | — | Vara and Collazos-Castro, 2019 | |
| PEDOT:PSS coated CF | Cylinder diameter:7 | 58.1 | — | — | — | — | −0.6–0.8 | up to about 100 | — | In vivo chronic recording both SU action potentials and LFPs chronically in the mice visual cortex for 5 weeks | Kozai et al., 2012 | |
| PEDOT: pTS coated CF | Cylinder diameter: 8.4 | 36.3 | — | — | 18.5 ± 2.6 | — | — | 118 ± 28 or 117.9 ± 28.4 | — | In vivo chronic recording in rat cortex for 31 days; In vivo chronic recording in rat motor cortex up to 154 days | Patel et al., 2015, 2016 | |
| PEDOT:TFP coated CF | Cylinder diameter: 4.5 | — | — | — | — | — | — | 170 ± 860 | — | In vivo chronic recording of both spontaneous and visual stimuli evoked activities from rat visual cortex for 55 days | Guitchounts and Cox, 2020 | |
| Iridium oxide film (EIROF) coated CF | Cylinder diameter: 8.5–12.5 | ∼385 or 600 | — | — | 17 | ∼25 | −0.6–0.6 | 57 or ∼100 | Ex vivo stimulation of in zebra finche tracheo syringeal nerve | In vivo acute recording from the tracheo syringeal nerve in zebra finches | Deku et al., 2018b; Gillis et al., 2018 | |
| N-UNCD coated CF | Cylinder diameter: 10 | 3,218 | — | — | 7.09 ± 3.65 | — | −1.8–1.2 | 25 | Ex vivo stimulation of rat retina | Ex vivo recording from rat retina; in vivo acute recording in wallaby visual cortex | Hejazi et al., 2020a | |
| B-CNW coated CF | Cylinder diameter: 10 | 3,218 | — | — | 7.82 ± 0.35 | — | −1.8–1.2 | 29.95 ± 13.53 | Ex vivo stimulation of rat retina | In vivo acute recording in wallaby visual cortex | Hejazi et al., 2020b | |
| CNT fiber produced by wet spinning | Cylinder diameter: ∼50 | 1,450 | — | — | 6.52 | — | −1.5–1.5 | 11.2 ± 7.6 | In vivo chronic stimulation of parkinsonian rat motor cortex | In vivo chronic recording from rat cortex for 3 weeks | Vitale et al., 2015 | |
| CNT fiber produced by dry spinning | Cylinder diameter: 5–20 or 20–100 | — | 9.7 ± 0.5 | bending stiffness = 8.16 × 10 3 or 1.58 × 102 nN.m | 3.52 ± 0.15 or 5.04 ± 0.22 (after acid nitric treatment) | 278.21 ± 5.42 | -0.6- 0.8 | 279.96 ± 32.08 or 41.95 ± 3.62 (after acid nitric treatment) | — | In vivo acute and chronic recording in rat ventral posteromedial nucleus of the thalamus and primary somatosensory cortex up to 5 months; In vivo chronic recording in mice cortex for 4 weeks | Xu and Gao, 2015; Lu et al., 2019; Tang et al., 2020 | |
| graphene encapsulated copper microwires | Cylinder diameter: 100 | — | — | — | — | — | — | ∼100 | — | In vivo acute and chronic recording of LFPs and SU action potentials in rat hippocampus for at least 4 weeks | Zhao et al., 2016 | |
| liquid crystal graphene oxide (LCGO) fiber | Cylinder diameter: 40–50 | — | 11.2 | — | 14 ± 0.9 | — | −1–0.9 | ∼5 | Ex vivo stimulation of rat retina | In vivo acute recording in feline visual cortex | Apollo et al., 2015; Xu and Gao, 2015. | |
| platinum coated LCGO fiber | Cylinder diameter: ∼20 or ∼40 | 169 ± 25 or 749 ± 93 | — | — | 10.34 | — | −1–0.9 | — | — | In vivo acute SU recording in rat cerebral cortex | Wang et al., 2019 | |
| graphene fiber | Cylinder diameter: 75 | — | 2–3 | — | 10.1 ± 2.25 | 889.8 ± 158.0 | −1.5–1.3 | 15.1 ± 3.67 | In vivo deep brain stimulation in a behaving Parkinson rat model | — | Zhao et al., 2020 | |
| polyethylene (CPE) and 5 wt% graphite fiber composites | Cylinder diameter: 200 | — | — | stiffness = 76.1–83.5 N/m | — | — | — | 1,310 ± 270 | In vivo optical stimulation of mouse cortex and hippocampus | In vivo chronic recording in mouse cortex and hippocampus for 3 months | Park et al., 2017 | |