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Rapid prototyping of carbon-based chemiresistive gas sensors on paper

Significance This paper describes a rapid, solvent-free, two-step procedure for the fabrication of selective gas and vapor sensors from carbon nanotubes and graphite on the surface of paper that overcomes challenges associated with solvent-assisted chemical functionalization and integration of these materials into devices. The first step generates solid composites from carbon nanotubes (or graphite) and small molecules (chosen to interact with specific types of gases and vapors) by mechanical mixing and subsequent compression into a form similar to a conventional pencil “lead”. The second step uses mechanical abrasion (“drawing”) of these solid composites on the surface of paper to generate functional devices. The use of diverse composites yields sensing arrays capable of detecting and differentiating gases and vapors and part-per-million concentrations. Chemically functionalized carbon nanotubes (CNTs) are promising materials for sensing of gases and volatile organic compounds. However, the poor solubility of carbon nanotubes hinders their chemical functionalization and the subsequent integration of these materials into devices. This manuscript describes a solvent-free procedure for rapid prototyping of selective chemiresistors from CNTs and graphite on the surface of paper. This procedure enables fabrication of functional gas sensors from commercially available starting materials in less than 15 min. The first step of this procedure involves the generation of solid composites of CNTs or graphite with small molecule selectors—designed to interact with specific classes of gaseous analytes—by solvent-free mechanical mixing in a ball mill and subsequent compression. The second step involves deposition of chemiresistive sensors by mechanical abrasion of these solid composites onto the surface of paper. Parallel fabrication of multiple chemiresistors from diverse composites rapidly generates cross-reactive arrays capable of sensing and differentiating gases and volatile organic compounds at part-per-million and part-per-thousand concentrations.