A remotely interrogatable magnetochemical pH sensor

A new type of sensor is presented that allows for remote, in-situ, continuous, long term monitoring of given chemical stimuli. The sensor is comprised of a thin polymeric layer made so that it swells in the presence of certain stimuli, bounded on each side by a magnetically soft thin film. The magnetic switching characteristics of the sensor are dependent upon the thickness of the intervening polymeric spacer layer. Placed within a sinusoidal magnetic field the sensor generates a series of voltage spikes in suitably located detecting coils. The magnitude of the voltage spikes are dependent upon how much the spacer layer has swollen in response to the given stimuli. The polymeric chemistry is very flexible, and can be made to selectively swell in response to, for example, moisture, pH, ion concentration, or atmospheric CO₂. The sensor principle has been demonstrated using lightly crosslinked poly (dimethylamino)-ethylmethacrylate to detect pH