A cross-reactive array of semiselective chemiresistive sensors made of polymer-graphene nanoplatelet (GNP) composite coated electrodes was examined for detection and discrimination of chemical warfare agents (CWA). The arrays employ a set of chemically diverse polymers to generate a unique response signature for multiple CWA simulants and background interferents. The developed sensors' signal remains consistent after repeated exposures to multiple analytes for up to 5 days with a similar signal magnitude across different replicate sensors with the same polymer-GNP coating. An array of 12 sensors each coated with a different polymer-GNP mixture was exposed 100 times to a cycle of single analyte vapors consisting of 5 chemically similar CWA simulants and 8 common background interferents. The collected data was vector normalized to reduce concentration dependency, z-scored to account for baseline drift and signal-to-noise ratio, and Kalman filtered to reduce noise. The processed data was dimensionally reduced with principal component analysis and analyzed with four different machine learning algorithms to evaluate discrimination capabilities. For 5 similarly structured CWA simulants alone 100% classification accuracy was achieved. For all analytes tested 99% classification accuracy was achieved demonstrating the CWA discrimination capabilities of the developed system. The novel sensor fabrication methods and data processing techniques are attractive for development of sensor platforms for discrimination of CWA and other classes of chemical vapors.

Escherichia coli O157:H7 (E. coli O157:H7) is one of the top pathogens of interest for the development of rapid diagnostic systems for food and water samples. The objective of this research is to develop a rapid, novel electrochemical biosensor based on the use of polypropylene microfiber membranes coated with a conductive polypyrrole and antibody functionalized for the biological capture and detection of E. coli O157:H7 in the field. Using glutaraldehyde, pathogen specific antibodies are covalently attached to conductive microfiber membranes which are then blocked using a 5% bovine serum albumin solution. The functionalized membranes are then exposed to E. coli O157:H7 cells washed in Butterfield's phosphate buffer and added to a phosphate-buffer electrolyte solution. When a voltage is applied to the system, the presence of the captured pathogen on the fiber surface results in an increase in resistance at the electrotextile electrode surface, indicating a positive result. In this study, the initial resistance of the membrane in the electrochemical system was established and found to range between 5.8 kΩ and 13 kΩ. The resistance of the system not associated with the electrotextile fibers was calculated to contribute to only 2.8% of the total system resistance, and found not to be significant. A proof of concept experiment was conducted and determined that the electrotextile electrode was able to differentiate between small changes in a solution's conductivity associated with the presence of E. coli O157:H7 cells over a concentration range of log 0-9 CFU/mL.

An electrotextile with a biosensing focus composed of conductive polymer coated microfibers that contain functional attachment sites for biorecognition elements was developed. Experiments were conducted to select a compound with a pendant functional group for inclusion in the polymer, a fiber platform, and polymerization solvent. The effects of dopant inclusion and post-polymerization wash steps were also analyzed. Finally, the successful attachment of avidin, which was then used to capture biotin, to the electrotextile was achieved. The initial results show a nonwoven fiber matrix can be successfully coated in a conductive, functionalized polymer while still maintaining surface area and fiber durability. A polypropylene fiber platform with a conductive polypyrrole coating using iron (III) chloride as an oxidant, water as a solvent, and 5-sulfosalicylic acid as a dopant exhibited the best coating consistency, material durability, and lowest resistance. Biological attachment of avidin was achieved on the fibers through the inclusion of a carboxyl functional group via 3-thiopheneacetic acid in the monomer. The immobilized avidin was then successfully used to capture biotin. This was confirmed through the use of fluorescent quantum dots and confocal microscopy. A preliminary electrochemical experiment using avidin for biotin detection was conducted. This technology will be extremely useful in the formation of electrotextiles for use in biosensor systems.

This Article reports methods to deposit iridium oxide nanoparticles (IrO x NPs) onto flexible materials for charge storage and the stable charge−discharge mechanism. In this work, IrO x NPs were electrodeposited onto commercially available flexible surfaces of both knit and nonwoven cotton and nonwoven carbon-based (carbon nanotubes and graphene) textile substrates. Carbon-coated cotton materials were fabricated by reducing graphene oxide on fabric. Flexible electrode materials were fabricated by either reducing graphene oxide on cotton fabric or binding carbon nanotubes/graphene into a free-standing platform. The IrO x NPs were then electrodeposited onto flexible platform samples by applying a positive potential to the fabric. After deposition, the resultant specific capacitance of the materials increased within the range from 192% to 2747% and was stable for over 1000 charge and discharge cycles.