Ultrasensitive detection of low-dose gamma radiation using polymeric thin films on microelectromechanical system-based sensors

A polymer-coated microelectromechanical system (MEMS) sensor was used in this study to detect electromagnetic nuclear radiation (gamma radiation) with high sensitivity. The resonance frequencies shift (RFS) resulting from the effect of gamma irradiation on the MEMS sensors coated with two polymeric thin films (polyacrylic acid [PAA] and polystyrene [PS]) were measured. The mechanical and optical properties of the coated polymer layers on Si wafers were evaluated before and after irradiation using atomic force microscopy (AFM) and ultraviolet-visible spectrophotometry. Further, surface roughness and reflectivity of the PS polymer thin film were found to be linear as a function of the gamma irradiation time. However, there was no noticeable change in the RFS, surface roughness, or reflectivity of the PAA polymer thin film. These results were confirmed using spectroscopic ellipsometry measurements which showed that the surface roughness increased linearly as a function of the gamma irradiation time. Based on these findings, the interaction between gamma radiation and PS polymer revealed that the MEMS coated with PS produced a linear response that could be used to develop radiation sensors for low gamma doses. Although many techniques exist for detecting nuclear radiation, the sensor proposed has ultrasensitivity, high measurement accuracy, and low cost.