High-sensitivity radio frequency noncontact sensing and accurate quantification of uric acid in temperature-variant aqueous solutions

A sodium-heparinized glass microcapillary tube-assisted radio frequency (RF) resonator-based noncontact sensor is developed for the accurate quantification of uric acid in aqueous solutions. To achieve high sensitivity, a newly proposed coupling structure between the systems of coupled resonators is exploited to form an efficient long sensing region with a highly concentrated electromagnetic field, thereby effectively miniaturizing the sensor and consequently enhancing the filling factor. The proposed sensor linearly detects the uric acid concentration (2-20 mg/dL) in temperature-variant (0-40 °C) aqueous solutions with a high sensitivity of 2.762 MHz mg^-1 dL^-1 and a reproducibility of 0.51% relative standard deviation.