Analysis of volatile organic compound droplets via wetting and evaporation using inkjet-printed carbon nanotube chemiresistors

Abstract

Volatile organic compounds (VOCs) are prevalent in food, environmental, and industrial systems, yet their liquid-phase analysis is often limited by bulky instrumentation and operational complexity. Here, inkjet-printed carbon nanotube (CNT) chemiresistors on paper are presented as a simple and accessible platform for analyzing microliter-scale droplets of VOCs and their binary mixtures. Upon droplet deposition, the device exhibits a characteristic resistance peak: an initial increase due to wetting, followed by a decrease as evaporation and desorption from CNTs become dominant. The time from droplet dispensing to the resistance peak, defined as the turnover time, shows strong correlation with the vapor pressure of VOCs, enabling compound differentiation. Analysis of binary mixtures, including ideal (benzene-toluene) and non-ideal (acetone-chloroform, benzene-methanol) systems, reveals information on intermolecular interactions. In addition, time-resolved turnover time measurements during evaporation allow tracking of compositional shifts, exemplified by the gradual enrichment of the less volatile component as the more volatile species evaporates. The method is further demonstrated using alcoholic beverages with varying ethanol concentrations, highlighting its applicability to real liquid samples encountered in practical settings. These results establish turnover time of CNT-based chemiresistors as a valuable metric for probing wetting, evaporation, and molecular interactions in multicomponent liquid systems, with potential applications in chemical sensing, environmental analysis, and quality control.