A Millimeter-Wave Sensor and Differential Filter-Paper-Based Measurement Method for Cancer Cell Detections

This paper introduces a novel, easily-designed millimeter-wave sensor and an innovative liquid sensing method, both suitable for biological sample detection and cancer cell discrimination. The sensor, composed of coplanar waveguides with load resonators, features a centrally symmetric stepped-impedance resonator that creates a detection region, capable of achieving multiple transmission poles and zeros. This resonator is responsive to the equivalent dielectric constant of the surrounding space, mirroring the electromagnetic properties of the tested sample via the resonant frequency and notch depth. The proposed sensing method uses filter paper to characterize a liquid's electromagnetic properties by comparing the S-parameters of dry and wet filter paper loaded onto the sensor. This method, an alternative to traditional microfluidic channels, allows all planar microwave/millimeter-wave solid dielectric constant sensors to robustly detect liquid materials. Applied to biomedicine, the design enables the sensor to generate multiple transmission peaks in the 20–60 GHz range, thereby facilitating discrimination of various cancer cell culture media and suspensions. Compared to traditional biochemical methods, this approach significantly reduces cancer detection costs and offers new avenues for label-free, real-time detection.