MEMS-integrated Coplanar Waveguide Ring resonator-based Label-free Sensor for Profenofos Detection

The detection and selective sensing of toxic chemical residues is critical for ensuring food safety and environmental health. We present a MEMS-based microcantilever sensor integrated with a coplanar waveguide (CPW) ring resonator for high sensitivity and selective analyte detection. The sensor facilitates real-time quantitative analysis by employing a label-free as well as single-step selective immobilization method, demonstrating its applicability to various analytes.

The presented CPW ring resonator-integrated MEMS-based microcantilever sensor was modelled and rigorously simulated using a numerical method based on the Finite Element Method (FEM). An operating frequency range of 30–60 GHz was considered in our numerical study. The microcantilever operating in the stress mode was functionalized with a profenofos-specific aptamer (SS2-55), which in turn enabled selective binding to the analyte profenofos, an organophosphorus insecticide. Molecular binding induces surface stress, causing cantilever deflection and a corresponding frequency shift in the S₁₁ parameter.

Significant shifts in the S₁₁ parameter were observed due to different actuation states induced by analyte binding. In its neutral state, the sensor initially exhibited two distinct S₁₁ dips: the primary dip at 53.96 GHz and the secondary dip at 47.48 GHz. Upon complete actuation of the microcantilever, the two dips are merged into a single S₁₁ dip at 50.4 GHz. The presented approach envisages a simpler fabrication protocol and robust system, while the optical methods normally demand sophisticated fabrication and analytical tools. Given these advantages, the detection limit of the presented sensor is 8.24 ng/ml(22.09 nM).

Our rigorous numerically studied CPW ring resonator MEMS sensing device enables the realization of a portable, robust, and precise sensor platform for detecting hazardous residues. The sensor’s adaptability to a broad spectrum of analytes based on an immobilized material makes it a versatile biosensing solution and can be tailored to the label-free detection of various analytes, including bioanalytes for point-of-care biomedical diagnostic and therapeutic devices.