Paper-Based Inkjet-Printed Carbon Nanotube Colorimetric Chemiresistors for Detection of Chemical Warfare Agents

Colorimetric papers have been widely used for the convenient and inexpensive detection of toxic chemicals including chemical warfare agents (CWAs). The majority of colorimetric papers, however, only detect liquid-phase analytes, exhibiting a limited gas-sensing performance. In this study, we report a colorimetric paper capable of detecting and identifying CWAs in both liquid and gas phases, achieved by inkjet-printing carbon nanotube (CNT)-based chemiresistors on the paper. The inkjet-printed CNTs generate electrical signals unique to liquid-phase CWAs (GB, VX) and their simulants without affecting the colorimetric responses, thereby enabling more accurate analyte identification. Inkjet printing can also be employed to noncovalently functionalize CNTs with various receptors. We fabricated a gas sensor array on the colorimetric paper by inkjet-printing three different receptors on the CNT chemiresistors and demonstrated the identification of four CWA simulants based on the response patterns of the array. This hybrid sensing platform, exhibiting both colorimetric and electrical signals, potentially serves as an inexpensive alternative to existing analytical tools for the analysis of CWAs and other toxic chemical compounds.