SAW Chemical Microsensors based on Nanostructured Carbon-based Thin Films
Résumé
Environmental concerns have been growing in the recent past, as a major issue worldwide. Sophisticated instruments and methods for sampling and analyzing are able to quantify a large spectrum of compounds at low concentrations. Among them, pollutants or disease biomarkers are of particular interest, like Volatile Organic Compounds, Heavy metals, specific biomarkers such as some proteins, endocrine disruptors have been the pollutants of major concern. They can be in the environment or in biological samples, in gaseous or liquid state: indoor/outdoor air, breath, biofluids like blood, serum, urine, etc. To complement the methodologies employed currently, we urgently need chemical and biological microsensors as dedicated solutions for on-site and real-time monitoring or early warning systems. Work done in our group, WAVES, at IMS Bordeaux, is geared to the development of such solutions.
In this Talk, we will focus on highly sensitive Surface Acoustic Wave-based devices (SAW), incorporating versatile resonant electronic component, combined with sensitive films based on carbon nanomaterials, which offer excellent surface specific as well as other advantages, including their mechanical properties, as well as the ease of deposition by friendly printing technologies. There is a growing interest on the use of such nanomaterials for sensing applications by incorporating them in SAW sensors. , , , We will present the results of our several studies made with Carbon NanoTube-based and Graphene or Graphene Oxide-based thin films, deposited on guided Shear-Horizontal SAW devices, also called Love wave devices, by using various methods such as inkjet printing or drop-casting. Experiments conducted in our labs to detect vapors such as ethanol or toluene, as well as the moisture, demonstrate the great potential of such structures for sensing applications at ambient temperature. For instance, we obtained a sensitivity of 15 Hz.ppm–1 with ethanol in nitrogen as inert carrier gas, from tests conducted with steps at fixed concentrations in the range from 30 to 1000 ppm. Fast response and good reversibility were observed in most cases. Such characteristics make C-based nanomaterials highly promising, compared to results previously obtained with other porous materials . Further chemical functionalization of CNTs or G-based materials is described to increase the sensitivity and, above all, to control the specificity and finally the selectivity of the microsensors. Interestingly, C-based films can be used with other types of microsensors, such as electromagnetic ones , that may offer a complementary signal, compared to the SAW device which is mainly based on mechanical effects only.
Acknowledgements. The results gathered in this paper were obtained with financial support, especially by the University of Bordeaux, the French National Research Agency (ANR-13-BS03-0010) and the French Embassy of Singapore (Merlion). The authors also warmly thank partners involved with us on these projects: LAAS-CNRS Toulouse (France), UPV Valencia (Spain), Forth (Greece), CINTRA (Singapore).