Planar SIW Cavity Based RF Sensor for Air Bubble Detection in Medical Industry

A novel planar RF sensor using the SIW cavity technique, operating at 2.45 GHz of the ISM band, is designed and presented for the air bubble detection dedicated to the medical industry. The proposed sensor is quite compact that requires only few microliter volume of the test liquid to effectively detect the air bubble inside the patient's IV line with high accuracy. The sensor design and optimization is realized using the full-wave numerical software, the CST-MWS in order to obtain the desired performance at the frequency of interest. The parameters of the proposed RF sensor are optimized such that its operating frequency corresponds to the dominant TE101 mode. The novel feed mechanism used in the proposed sensor helps to obtain the improved Q-factor as compared to conventional planar resonant sensors. The prototype of the proposed sensor is fabricated on a 1.6 mm thick, Rogers RT5880 substrate. The scattering parameters of the fabricated sensor under the unloaded condition are measured and are found to closely match with the corresponding simulated data which actually validates the proposed design. Thereafter, various liquid chemicals are measured to record the change in measured resonant frequency in accordance with their dielectric constant. Finally, the proposed scheme is successfully tested for the detection of an air bubble inside the patient's typical IV saline line under practical condition.