Monitoring of Pesticides in Air using Liquid Crystal Sensors – OPAL

Air pollution by pesticides is a component of atmospheric pollution that remains less documented than other environments (water, soil, food) and represents a topical health problem. Furthermore, there is a lack of tools to monitor respiratory exposure to pesticides during spray application or post application. The objective of the project OPAL is to answer it by providing portable devices for on-site and real time monitoring of pesticides in air. To do this, transducers based on the principle of anchoring transition of liquid crystals (LCs) will be used. Research will focus on identifying interfaces having a high selectivity in the anchoring transition of a LC in presence of a target pesticide, first from molecular modelling and then by experimental tests. The work carried out in this project will also concern the development of LC transducers combining the LC with a substrate modified with either an anchoring or orientational layer (depending on transducer configuration), eventually an aqueous layer, and a protective porous membrane. The orientation change from nematic phase to disorder phase after anchoring transition will be monitored by polarimetric optics as the LC transition is accompanied by a change in the birefringence. During OPAL project, reliable and robust technological processes for transducers fabrication will be developed and then several LC transducers based on different interfaces will be associated to form an array which global response will be a characteristic signature of a pesticide. Finally, full sensors will be realized by associating the transducers with LEDs and photodiodes and integrating them with an electronic card to follow LC transition by measuring the photocurrent. Furthermore, algorithms to process the signal and extract information on the presence and / or content of pesticide that will be developed. To assess and characterize the performance of the LC interfaces, the transducers and the sensors throughout the project, it is also planned to build and qualify a pesticide aerosol generation and an exposure room. The tests carried out in this room will also serve to select and optimize the design of the sensor. At the end of the project, the sensors can be tested outdoor especially in active area and confronted to standard analysis of the Air Breizh association in charge of monitoring air quality in Britany and which foresees a campaign during the project.
The project consortium, composed of two public structures and involving three teams, brings together the following areas of expertise: functionalization and characterization of surfaces, technological processes, electronics, development of sensors and their integration, aerosols generation and characterization, and fluid mechanics. Thus, the complementarity of the consortium is a real asset for the development of functional prototypes.