RF inductive sensors for detection of change in the ionic strength and pH of liquid samples

The use of inductors operating in the radio frequency region of 10 MHz to 1 GHz for detection of a change in concentration of ionic species present in a liquid sample is reported here. Liquid samples under constant ionic strength and varying pH along with constant pH and varying ionic strength were used for testing purposes. Y-parameters were extracted and used for data analysis. A change of 15.3 MHz in the resonant frequency of the inductor under varying pH and a change of 20MHz under the constant pH condition was obtained. The results from this study show that inductors can be employed in designing simple, scalable and integrable sensing systems to perform label free analysis without the need for surface activation or perturbing the system under study. This design has the potential in being used for certain applications like monitoring DNA hybridization or gastric juice.