Integrating a Microwave Resonator and a Microchannel with an Immunochromatographic Strip for Stable and Quantitative Biodetection.

An immunochromatographic strip is an effective diagnostic tool in various fields because of its simplicity, rapidity, and cost-effectiveness. However, typical strips for preliminary screening provide only qualitative or semiquantitative results, and common solutions for quantitative detection by incorporating different kinds of nanoparticles as biomarkers still do not solve this problem thoroughly. Here, we try to tackle this challenge by integrating low-cost membrane-compatible square split-ring resonators and structure-design-flexible microchannels with flexible strips. We experimentally demonstrate that the limit of detection (LOD) and sensitivity of the strip for quantitative detection of Staphylococcus aureus reach 0.784 ng/mL and 10.214 MHz/(ng/mL), respectively. The LOD level is about 63 times higher than that of the color-based strip determined by the naked eye, and the stability is about 18 times higher than that of the fluorescent strip. This work could not only provide a powerful diagnosis tool for the quantitative detection of S. aureus or other molecules but also deliver new avenues for achieving electric field detection of biomolecules, system-level integration of biosensors, and the development of portable diagnostic devices.