Evaluation of Polymer-Coated Carbon Nanotube Flexible Microelectrodes for Biomedical Applications

The demand for electrically insulated microwires and microfibers in biomedical applications is rapidly increasing. Polymer protective coatings with high electrical resistivity, good chemical resistance, and a long shelf-life are critical to ensure continuous device operation during chronic applications. As soft and flexible electrodes can minimize mechanical mismatch between tissues and electronics, designs based on flexible conductive microfibers, such as carbon nanotube (CNT) fibers, and soft polymer insulation have been proposed. In this study, a continuous dip-coating approach was adopted to insulate meters-long CNT fibers with hydrogenated nitrile butadiene rubber (HNBR), a soft and rubbery insulating polymer. Using this method, 4.8 m long CNT fibers with diameters of 25–66 µm were continuously coated with HNBR without defects or interruptions. The coated CNT fibers were found to be uniform, pinhole free, and biocompatible. Furthermore, the HNBR coating had better high-temperature tolerance than conventional insulating materials. Microelectrodes prepared using the HNBR-coated CNT fibers exhibited stable electrochemical properties, with a specific impedance of 27.0 ± 9.4 MΩ µm2 at 1.0 kHz and a cathodal charge storage capacity of 487.6 ± 49.8 mC cm−2. Thus, the developed electrodes express characteristics that made them suitable for use in implantable medical devices for chronic in vivo applications

Electrochemical Quantification of Lead Scale Particulates in Drinking Water

Lead contamination in drinking water can be caused by various types of lead: lead ions, soluble lead complexes, and lead particulates. Traditional detection methods such as inductively coupled plasma mass spectroscopy (ICP-MS) and atomic absorption spectroscopy (AAS) can detect all types of lead because of sample preparation. Nevertheless, these methods are expensive and require trained personnel. As electrochemical techniques are less expensive, portable, and easy to use, they are a promising alternative for lead detection in drinking water. However, electrochemistry is typically only able to detect lead ions. In this work, lead scales collected from a lead pipe are characterized to determine the types of lead compounds present within the lead corrosion scale. Subsequently, membrane electrolysis (ME) is used to acidify a drinking water solution containing lead corrosion scales, allowing for the dissociation of the particulate lead into lead ions. Square-wave anodic stripping voltammetry (SWASV) is then applied to determine the current associated with the lead ions being stripped off the working electrode, which originated from the particulates in the scales. Standard addition is used to determine the concentration of lead associated with the current response. This technique is compared to ICP-MS, and the relative errors between the two methods show that ME combined with SWASV is a viable approach for detecting lead contamination in drinking water due to lead corrosion scales