Proceedings Article | 1 May 2009
KEYWORDS: Sensors, Resistance, Thin films, Polymers, Electrodes, Polymeric sensors, Polymer thin films, Chemical analysis, Chromatography, Crystals
The financial losses and destruction of crops due to insect infestation in the United States are estimated by the
USDA to exceed 20 billion dollars annually. Much of these losses could be avoided by having a sensor that could
effectively identify the early stages of insect infestation. However, traditional detection methods are time consuming,
require trained personnel, and are not sufficient for early detection. Several previous research studies showed that
emitting organic volatile compounds is a defensive mechanism activated by some plant species after being attacked by
herbivores and parasites. Corn, cotton, pine, Brussels sprouts when attacked by Beet army worm, spider mites, bark
beetles and caterpillars respectively, emits different blends of plant volatiles including γ-terpinene, α-pinene, p-cymene,
farnesene, limonene and cis-hexenyl acetate, with a concentration of about 50 ppm. Therefore, monitoring for these
volatile compounds may enable on-site early detection of insect infestations. In this study, a chemical resistor sensor to
detect plant volatiles was designed and fabricated. The sensor platform consists of micro electronically fabricated
interdigitated electrodes. On to this platform, a poly3-hexylthiophene (P3HT) thin film was deposited, using a spin
coater at 8000 rpm for 30 seconds. The sensor was tested and found to be sensitive to a variety of plant volatiles,
including γ-terpinene, α-pinene, p-cymene, farnesene, limonene and cis-hexenyl acetate at room temperature. These
vapors interacted with the P3HT film causing an increase in the resistance of the sensor by more than one order of
magnitude
