(736c) Optimization of a Multi-Phase Sensor for Detection of Phosphonates In Air

The objective of this paper is to report the modeling and optimization of a new MEMS- based phosphonate sensor that utilizes a porous membrane between a gas and a liquid stream to allow operation at low liquid and high gas flow rates. Previous work from our laboratory has demonstrated that phosphonate molecules can be detected with such a device, but the sensitivity was insufficient for certain applications (e.g. detection of pesticides in foodstuffs).

In this paper COMSOL simulations and design of experiments were used to optimize the device. We find that both the simulation and the experiment show that i) the size and hydrophilicity of the pores in the membranes and ii) the liquid channel height make the most difference to the sensor response. For example, we calculate that the response increases by 41 mV/mm as the channel depth decreases and the experiments show a 296 mV/mm change for decreased channel depths. Also, by optimizing the geometry the sensitivity of the device could be enhanced. The optimized device can detect 109 molecules with good signal to noise.