Metal organic framework (MOF) materials are a class of hybrid organic-inorganic crystalline materials whose pore structures and chemical properties can be tailored by the selection of component chemical moieties. Many MOFs have extraordinary intrinsic surface areas, capable of adsorbing large quantities of other chemicals, such as volatile organic compounds or moisture. Upon absorption of guest molecules, many MOFs undergo reversible changes in the dimensions of their unit cells. These properties suggest several routes to chemical sensing in which the transduction mechanisms are: 1) the stress induced at an interface between a flexible MOF layer and a static microcantilever fabricated with a built-in piezoresistive stress sensor; 2) the change in the resonant frequency of an oscillating microcantilever induced by mass adsorption; and 3) the change in the resonant frequency of a acoustic sensor, such as a surface acoustic wave (SAW) sensor through changes in mass loading and film moduli. This paper focuses on humidity sensing by SAWs coated with Cu3(BTC)2 (HKUST-1) over a very broad concentration range.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.