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 CrO4^2- in aqueous solutions. These microcantilevers undergo bending deflection upon exposure to solutions containing various CrO4^2- 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 microcantileverbased chemical and biological sensors when molecular recognition agents are immobilized in the hydrogel.