Detection of CrO₄^2- using a hydrogel swelling microcantilever sensor

Hydrogels containing various mounts of tetraalkylammonium salts were used to modify microcantilevers for measurements of the concentration of CrO ₄^2- in aqueous solutions. These microcantilevers undergo bending deflection upon exposure to solutions containing various CrO ₄^2- concentrations as a result of swelling or shrinking of the hydrogels. The microcantilever deflection as a function of the concentration of CrO₄^2- ions is nearly linear in most concentration ranges. It was found that a concentration of 10^-11 M CrO₄^2- can be detected using this technology in a fluid cell. Other ions, such as Br^-, HPO₄^2-, and NO₃^-, have minimal effect on the deflection of this cantilever. The anions SO₄^2- and CO₃ ^2- could interfere with the CrO₄^2- detection, but only at high concentrations (> 10^-5 M). Such hydrogel-coated microcantilevers could potentially be used to prepare microcantilever-based chemical and biological sensors when molecular recognition agents are immobilized in the hydrogel.