This Small Business Innovative Research Phase I project will develop a novel type of miniature mercury sensor utilizing very recent developments in microcantilevers. Sensors based on this technology will be up to 103 times smaller, considerably more sensitive, and less expensive than currently available mercury sensors. Microcantilevers that are 50-200 (m long, 10-40 (m wide, and 0.3-3 (m thick and possessing resonance frequencies in the range 10-300 kHz, have recently been used in scanning force microscopy to detect extremely small changes in force in the range of 10-12-10-9 N. The resonance frequency (and bending) of the microcantilever varies reproducibly and sensitively due to adsorption of molecules on the cantilever surfaces making it an ideal chemical sensor with picogram sensitivity and parts per billion detection. Preliminary mercury detection studies, have demonstrated detection of ppb of Hg, and have shown that selective adsorption of mercury on gold coated cantilevers (end loading) produces a linear variation in resonance frequency with a sensitivity of 0.8 pg/Hz. Simultaneous bending measurements resulted in a sensitivity of 0.6 pg/mV. The recyclability of the mercury sensor will be demonstrated by removing the adsorbed mercury by heating the sensor. Exploiting the microcantilever response, combined with selective removal of interfering molecules (such as H2S) using filters, microcantilevers will be shown to be extremely versatile and novel mercury pollution sensors. We plan to demonstrate that the sensor can be vibrated in liquid environments with a reasonable Q, allowing it to be used to detect the presence of mercury in these environments. Additionally, due to the extremely small size of the sensor, the development of a personal monitor that is highly sensitive may be possible. The proposed work will provide a highly significant advance in microcantilever sensor technology with possibilities of developing new sensors for other chemicals. Commercial applications of mercury sensors include industrial hygiene, air and water pollution control, mining industry, submarines, air quality monitoring, etc.
