Abstract
Airborne particulate matter, both in the workplace and the environment, has been linked to adverse health effects, this in turn has led to the establishment of legislation stipulating exposure limits. Advances in technology, and associated increased use of nanomaterials means that such regulations and associated monitoring remain highly relevant. Monitoring techniques used for airborne particulates are costly, bulky and insensitive to low to medium exposure to nanomaterials. Capacitance based sensors, detecting changes in electrical impedance due to the presence of nanomaterials have been developed in this work. Capacitive interdigitated electrodes integrated with nanoparticulate trapping structures have been designed and manufacturing techniques suitable for mass manufacture have been evaluated and developed. Photolithographic and inkjet printing based methods for manufacturing electrodes were evaluated, identifying inkjet printing as the most appropriate technique, providing good reproducibility, ease of fabrication and the ability to rapidly tailor electrode structures to provide different capabilities. It was found that higher sensitivities were obtained when gap widths between electrodes decreased. Two trapping layers were evaluated, columnar Zinc oxide with pore sizes of 10nm to 170nm, and porous polystyrene with sizes of 10µm to 50µm. Whilst offering small pore sizes, potentially allowing the trapping and detecting of a smaller particle size distribution, under test conditions zinc oxide structures were shown to be too fragile to survive real life test events. Porous polystyrene structures were shown to have lower selectivity trapping all particles between 20-200nm, however these trapping structures were shown to withstand real life test events. Analytical modelling has shown good agreement with experimental test results and has been used to predict the devices response to different nanomaterials offering the potential that the capacitance based sensors could also be used to differentiate between different nanomaterials.