MOF @ MEMS: Design optimization for high sensitivity chemical detection

Metal Organic Frameworks (MOFs) are a rapidly developing class of nanoporous materials with numerous applications in diverse fields such as chemical detection, hazardous gas detection, and carbon capture. Even though numerous articles have been written emphasizing the adsorption properties of these MOFs, their compatibility with respect to the sensing device has not been explored. While there are numerous types of sensing devices that could benefit from the use of MOF-based coatings to enhance sensitivity and selectivity, we are particularly interested in microcantilevers because of the high sensitivity they can provide within a compact, lower-power architecture. In this paper, we address this need by analyzing the effect of the mechanical properties of MOFs on the sensor response. In particular, we are interested in the structural flexibility of MOFs, because this unique guest-induced property can be used for strain-induced sensing attribute of the microcantilever. In this regard we examined the effects of important MOF mechanical properties such as the Young's Modulus, Poisson's ratio, and density on the sensor response for a range of values representative of the MOFs available in the literature. From our analysis we determined that increasing the Young's Modulus and Poisson's ratio improve the response, while the density of the MOF has a negligible effect on the cantilever response. In addition, we also examined the influence on cantilever response of the intermediate layer used to bind the MOF, from which we observe that SiO2 provides the best sensor response for a given MOF layer.