Dr. Yan Cui of the Bio-Microelectronics and Healthcare Laboratory and his collaborator have reported the research progress in the high-sensitive microwave sensors. A novel approach to ultra-high quality factor (Q) in the split-ring resonator with active feedback loop was proposed, which utilized a phase shifter to tune equivalent negative resistance for accurate loss compensation. The paper titled by “A Tunable High-Q Microwave Detector for On-Column Capillary Liquid Chromatography” was accepted for publication inIEEE Transactions on Instrumentation and Measurement.This research work was conducted in the School of Microelectronics, Shandong University. Dr. Yan Cui is the first and corresponding author of the paper.
In the modern analytical science, miniaturized capillary columns for liquid chromatography (LC) with inner diameters of several to hundreds of micrometers attract a great interest in efforts to reduce sample and solvent consumptions. As a result, the higher sensitivity of detection is urgently demanded for downscaled capillaries due to lower injection amounts. Dr. Yan Cuiet alproposed an on-column microwave detector to maintain the integrity of LC system without compromise on sensitivity. Based on a phase-tunable active feedback loop, losses were accurately compensated for maximizing loaded Q, as high as 4.0×106at ~ 3.89 GHz. With the stop-flow mode, different concentrations between 40 and 150 mg/dL were measured, which covered the normal blood glucose levels. The minimum detectable quantity of glucose was ~ 18.8 ng with an effective sample volume of ~ 47 nL. The plug-unplug mode provided fast and flexible sampling and analysis.
