Flexible microwave sensors for real-time analysis of water contaminants

This paper reports on the development of novel microwave sensors for water contaminant analysis in real time. In particular, changes in the microwave part of the electromagnetic spectrum are used as an indicator of water quality. The sensing element was designed on a flexible substrate in order that it is less prone to failure due to mechanical damage, thus providing longevity. This also allows for a broad range of applications where a sensor, or sensors, could be placed in water reservoirs or water pipes. The sensing element consists of silver metal patterns which form interdigitated electrodes (IDE) in various configurations on polyimide flexible laminate substrates. The effect of IDE sensor configuration on the sensitivity of reflected signals represented by S-11 parameters was studied. The developed system confirmed the viability of using microwaves for real-time water quality monitoring as the corresponding spectra for air, deionised water and tap water were unique with clearly observed shifts in the resonant frequencies of the sensors when placed in direct contact with various water samples.