Detection of Femtomolar Concentrations of HF Using an SiO ₂ Microcantilever

Femtomolar concentrations of hydrogen fluoride a decomposition component of nerve agents, were detected using a SiO ₂ microcantilever. The microcantilever underwent bending due to the reaction of HF with SiO ₂. The microcantilever deflection increased as the concentration of HF increased. Other acids, such as HCl, had no effect on the deflection of the cantilever. The mechanism of reaction-induced bending and the correlation of microcantilever deflection with the HF concentration are discussed. The deflection in response to HF of a commercially available silicon cantilever was also studied, and its response was compared with that of the SiO ₂ cantilever. Much less bending amplitude and sensitivity were observed for the silicon cantilever.