Benchtop Carbon Fiber Microelectrode Array Fabrication Toolkit

BackgroundConventional neural probes are primarily fabricated in a cleanroom, requiring the use of multiple expensive and highly specialized tools.New methodWe propose a cleanroom “light” fabrication process of carbon fiber neural electrode arrays that can be learned quickly by an inexperienced cleanroom user. This carbon fiber electrode array fabrication process requires just one cleanroom tool, a parylene-c deposition machine, that can be learned quickly or outsourced to a commercial processing facility at marginal cost. Our fabrication process also includes hand-populating printed circuit boards, insulation, and tip optimization.ResultsThe three different tip optimizations explored here (Nd:YAG laser, blowtorch, and UV laser) result in a range of tip geometries and 1kHz impedances, with blowtorched fibers resulting in the lowest impedance. While previous experiments have proven laser and blowtorch electrode efficacy, this paper also shows UV laser cut fibers can record neural signals in vivo.Comparison with existing methodsExisting carbon fiber arrays either do not have individuated electrodes in favor of bundles or require cleanroom fabricated guides for population and insulation. The proposed arrays use only tools that can be used at a benchtop for fiber population.ConclusionsThis carbon fiber electrode array fabrication process allows for quick customization of bulk array fabrication at a reduced price compared to commercially available probes.

Effects of Carbon Fiber Compression Ratio and Electrolyte Flow Rate on the Electrochemical Performance of Vanadium Redox Batteries

All-vanadium flow batteries (VRFBs) are used in the field of energy storage due to their long service life and high safety. In order to further improve the charge-discharge performance of VRFB, this study mainly used the comparative evaluation of VRFB’s carbon fiber electrode compression ratio and electrolyte flow rate. The battery is charged and discharged under different current densities, different compression ratios, and different flow rates. The results show that increasing the compression ratio at different current densities can reduce the internal resistance of the battery, but an excessive compression ratio will accelerate the transfer of vanadium ions, increase the deviation of the electrolyte, and reduce the Coulombic efficiency of the battery. The performance of the battery tends to be balanced when the compression ratio is 30%. At the same time, in the case of the same compression ratio, increasing the flow rate of the electrolyte can reduce the internal reaction resistance of the battery. When the flow reaches a certain value, the influence on the internal resistance will be smaller.

One-step electropolymerization of methylene blue films on highly flexible carbon fiber electrode as supercapacitors

Energy crisis and environmental pollution have been one of the major global issues. In this regard, the search for new energy storage materials is cheap, flexible and high-performance supercapacitors electrode which has become intensive. Also, reducing the amount of organic dyes polluting in water is a great significance. Herein, one-step electropolymerization of methylene blue on carbon fiber and the resulting films were applied to the supercapacitor. The high performance is associated to the outstanding conductivity, electrochemical stability and superior mechanical flexibility of carbon fiber. A new flexible electrode for supercapacitors was successfully fabricated by demonstrating with a good electrochemical performance and a promising alternative to reduce the water pollution.

Sharpened and mechanically robust carbon fiber electrode arrays for neural interfacing

ObjectiveBioelectric medicine offers therapeutic diagnoses and treatments for disorders of the nervous system unresponsive to pharmacological treatments. While current neural interfaces effectively treat many disorders with stimulation, recording specificity is often limited to gross averages across many neurons or axons. Here, we develop and describe a novel, robust carbon fiber electrode array adaptable to many neural structures for precise neural recording.ApproachCarbon fibers were sharpened using a blowtorch method made reproducible by using the reflection of fibers against the surface of a water bath. Arrays of carbon fibers were developed by partially embedding carbon fibers in medical-grade silicone to improve robustness to fracture. Acute spontaneous electrophysiology was recorded from the rat cervical vagus nerve, feline dorsal root ganglia, and rat brain. Acute brushing and bladder pressure electrophysiology was recorded from feline dorsal root ganglia as well.Main resultsBlowtorching resulted in fibers of 72.3 ± 33.5 degree tip angle with 146.8 ± 17.7 μm exposed carbon. Silicone-embedded carbon fiber arrays were robust to bending (87.5% of fibers remained unbroken, 50,000 passes). Observable neural clusters were recorded using sharpened carbon fiber electrodes from rat cervical vagus nerve (41.8 μVpp, N=3 electrodes), feline dorsal root ganglia (101.1 μVpp, N=32 electrodes), and rat brain (80.7 μVpp, N=7 electrodes). Recordings from the feline dorsal root ganglia included physiologically-relevant signals from increased bladder pressure and cutaneous brushing.SignificanceThese results suggest that this carbon fiber array is a uniquely robust and adaptable neural recording device, useful for specific electrophysiology measurements. In the future, this device may be useful as a bioelectric medicine tool for diagnosis and closed-loop neural control of therapeutic treatments and monitoring systems.

CoMnO2-Decorated Polyimide-Based Carbon Fiber Electrodes for Wire-Type Asymmetric Supercapacitor Applications

In this work, we report the carbon fiber-based wire-type asymmetric supercapacitors (ASCs). The highly conductive carbon fibers were prepared by the carbonized and graphitized process using the polyimide (PI) as a carbon fiber precursor. To assemble the ASC device, the CoMnO2-coated and Fe2O3-coated carbon fibers were used as the cathode and the anode materials, respectively. Herein, the nanostructured CoMnO2 were directly deposited onto carbon fibers by a chemical oxidation route without high temperature treatment in presence of ammonium persulfate (APS) as an oxidizing agent. FE-SEM analysis confirmed that the CoMnO2-coated carbon fiber electrode exhibited the porous hierarchical interconnected nanosheet structures, depending on the added amount of APS, and Fe2O3-coated carbon fiber electrode showed a uniform distribution of porous Fe2O3 nanorods over the surface of carbon fibers. The electrochemical properties of the CoMnO2-coated carbon fiber with the concentration of 6 mmol APS presented the enhanced electrochemical activity, probably due to its porous morphologies and good conductivity. Further, to reduce the interfacial contact resistance as well as improve the adhesion between transition metal nanostructures and carbon fibers, the carbon fibers were pre-coated with the Ni layer as a seed layer using an electrochemical deposition method. The fabricated ASC device delivered a specific capacitance of 221 F g−1 at 0.7 A g−1 and good rate capability of 34.8% at 4.9 A g−1. Moreover, the wire-type device displayed the superior energy density of 60.2 Wh kg−1 at a power density of 490 W kg−1 and excellent capacitance retention of 95% up to 3000 charge/discharge cycles.