This Small Business Innovation Research (SBIR) Phase I project aims to develop a commercially viable, highly portable, and cost-effective electronic gas sensor chip for detecting the plant hormone ethylene. Measuring ethylene allows an estimate of fruit ripeness and the sensor chips can thus be utilized to guide decisions that lead to a reduction in waste and spoilage of produce in agriculture, storage, transportation, and distribution. This approach has three key innovations. (1) The technology is scalable, cost-effective, and the sensor output is a simple resistance measurement. The sensor is a paper-based chemiresistive sensor chip (the size of a business card). Metal electrodes form a circuit with single-walled carbon nanotubes (SWCNTs) specially functionalized to selectively detect ethylene gas in a complex chemical environment. (2) Novel solid-state sensing material formulations for ethylene detection will be developed. This biomimetic approach enables detection of ethylene in real-world confounding conditions at concentrations below 1 ppm at 10x-100x lower cost than current solutions. (3) Mass production and rapid prototyping are proposed through a modular, rapid, scalable, and solvent-free manufacturing method. This innovative, but simple manufacturing method is analogous to drawing with pencil on paper. The broader impact/commercial potential of this project is the reduction of produce wasted by spoilage that results in losses of ca. $20BN per year. Innovative strategies are needed for reducing produce spoilage including selling at peak ripeness, or promptly removing spoiled produce from the supply chain to avoid cross-contamination. Measuring ethylene is key to food supply chain management to aid in these efforts. Current methods for detecting ethylene, are cumbersome, expensive, complex, and/or do not meet other necessary performance requirements for large scale implementation. Traditional laboratory level sensing methods such as photoacoustic spectroscopy or gas chromatography are used to measure ethylene. The required instruments are, however, bulky, expensive and require trained personnel. Handheld ethylene sensors (typically electrochemical) have recently become available, but their prices of ca. $1,000 are prohibitively expensive for most food sensing applications. As a result, companies in food production, storage, transport, and retail, are interested in the ethylene sensors. Additionally, sensor companies (general and in the food sector) who do not have ethylene sensing capabilities are very interested in ethylene sensing technology.
