Ethylene is a gaseous plant hormone. Ripe fruit gives off ethylene, and many fruits ripen faster when exposed to it. Fruit producers use high concentrations of ethylene to ripen fruit in the warehouse so it is ready to eat when it reaches consumers. Inexpensive, accurate ethylene sensors would enable better control of that process. It would also allow retailers to avoid wastage by monitoring fruit ripeness.
Today's ethylene detection systems are lab-scale, expensive table-top devices, limiting their usefulness in fruit distribution and retail. The new ethylene sensor, developed by imec and Holst Centre, offers the same functionality in a single chip. To achieve this, the researchers have created a novel electrochemical cell based on an ionic liquid. Because ionic liquids cannot evaporate at room temperatures, they can be used in very thin layers in the cell. This means the cell – and hence the entire sensor – can be much smaller while delivering the same performance.
A first-generation prototype of this sensor detects ethylene down to 1 part per million (ppm), with a linear response up to 10ppm – the kind of concentrations typically used to ripen fruit artificially. Imec and Holst Centre recently produced a second-generation prototype on an inexpensive, flexible substrate, paving the way for use in smart packaging. Work is continuing to further miniaturize the sensor, to extend its sensitivity to sub-ppm for monitoring natural ripening, and to test it in real-life fruit storage and transportation conditions.
The ethylene sensor uses an electrochemical sensing mechanism. A voltage is applied between a gold electrode and a reference electrode. At the electrode surface, the ethylene is oxidized, which means that electrons are transferred from molecules in the ionic liquid to the electrode, resulting in a current. The magnitude of this current scales with the ethylene concentration in the gas phase.
About IMEC
Imec performs world-leading research in nanoelectronics. Imec leverages its scientific knowledge with the innovative power of its global partnerships in ICT, healthcare and energy. Imec delivers industry-relevant technology solutions. In a unique high-tech environment, its international top talent is committed to providing the building blocks for a better life in a sustainable society. Imec is headquartered in Leuven, Belgium, and has offices in Belgium, the Netherlands, Taiwan, US, China, India and Japan. Its staff of about 1,900 people includes more than 500 industrial residents and guest researchers. In 2010, imec's revenue (P&L) was 285 million euro. Further information on imec can be found at www.imec.be.
Imec is a registered trademark for the activities of IMEC International (a legal entity set up under Belgian law as a "stichting van openbaar nut”), imec Belgium (IMEC vzw supported by the Flemish Government), imec the Netherlands (Stichting IMEC Nederland, part of Holst Centre which is supported by the Dutch Government), imec Taiwan (IMEC Taiwan Co.) and imec China (IMEC Microelectronics (Shangai) Co. Ltd.) and imec India (Imec India Private Limited).
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Source: IMEC
