In this paper we demonstrate the potential for novel nanoporous framework materials (NFM) such as metal-organic
frameworks (MOFs) to provide selectivity and sensitivity to a broad range of analytes including explosives, nerve
agents, and volatile organic compounds (VOCs). NFM are highly ordered, crystalline materials with considerable
synthetic flexibility resulting from the presence of both organic and inorganic components within their structure.
Detection of chemical weapons of mass destruction (CWMD), explosives, toxic industrial chemicals (TICs), and volatile
organic compounds (VOCs) using micro-electro-mechanical-systems (MEMS) devices, such as microcantilevers and
surface acoustic wave sensors, requires the use of recognition layers to impart selectivity. Traditional organic polymers
are dense, impeding analyte uptake and slowing sensor response. The nanoporosity and ultrahigh surface areas of NFM
enhance transport into and out of the NFM layer, improving response times, and their ordered structure enables structural
tuning to impart selectivity. Here we describe experiments and modeling aimed at creating NFM layers tailored to the
detection of water vapor, explosives, CWMD, and VOCs, and their integration with the surfaces of MEMS devices.
Force field models show that a high degree of chemical selectivity is feasible. For example, using a suite of MOFs it
should be possible to select for explosives vs. CWMD, VM vs. GA (nerve agents), and anthracene vs. naphthalene
(VOCs). We will also demonstrate the integration of various NFM with the surfaces of MEMS devices and describe
new synthetic methods developed to improve the quality of VFM coatings. Finally, MOF-coated MEMS devices show
how temperature changes can be tuned to improve response times, selectivity, and sensitivity.
In this paper, we report on using polydimethylsiloxane (PDMS) tools to emboss cyclic olefin copolymer (COC). Positive photoresist AZP 4620 was used to fabricate 5 and 20 μm thick PDMS tools. The embossed microchannels were 10 μm to 100 μm in width at 10 μm to 100 μm in spacing. The COC embossing parameters, including temperature, force, and time were optimized to reduce replication errors. The optimized process was then successfully applied to fabrication of a passive microfluidic mixer designed and simulated using CFDRC ACE+.
A new passive micromixer has been developed with a low dependence on Reynolds number. The mixer design contains obstructions inside the mixing microchannels to breakup the flow resulting in chaotic mixing. Using CFDRC ACE+ software the mixer was modeled and was shown to completely mix water and glycerin in less than 1 cm. The micromixer was fabricated in cyclic olefin copolymer (COC) using hot embossing with polydimethylsiloxane (PDMS) tools and evaluated using epifluorescence microcopy.