Microfluidic Biosensor Based on Microwave Substrate-Integrated Waveguide Cavity Resonator

Abstract

A microfluidic biosensor is proposed using a microwave substrate-integrated waveguide (SIW) cavity resonator. The main objectives of this noninvasive biosensor are to detect and analyze biomaterial using tiny liquid volumes (3 μL). The sensing mechanism of our proposed biosensor relies on the dielectric perturbation phenomenon of biomaterial under test, which causes a change in resonance frequency and return loss (amplitude). First, an SIW cavity is realized on a Rogers RT/Duroid 5870 substrate. Then, a microwell made from polydimethylsiloxane (PDMS) material is loaded on the SIW cavity to observe the perturbation phenomenon. The microwell is filled with phosphate-buffered saline (PBS) solution (reference biological medium). To demonstrate the sensing behavior, the fibroblast (FB) cells from the lungs of a human male subject are analyzed and one-port S-parameters are measured. The resonance frequency of the structure with FB cells is observed to be 13.48 GHz. The reproducibility and repeatability of our proposed biosensor are successfully demonstrated through full-wave simulations and measurements. The resonance frequency of the FB-loaded microwell showed a shift of 170 MHz and 20 MHz, when compared to those of empty and PBS-loaded microwells. Its analytical limit of detection is 213 cells/μL. Our proposed biosensor is noncontact and reliable. Furthermore, it is miniaturized, inexpensive, and fabricated using simple- and easy-design processes.

Review of Recent Metamaterial Microfluidic Sensors

“…Analytical LOD can be calculated as LOD = 3.3 × (Standard Deviation of blank response/Slope of calibration curve) where the LOD is represented with the same units as that of concentration. For example, in [ 28 ], concentration of Fibroblast cells taken from a human male subject are detected in the range of 0 to 2000 cells/µL using a microfluidic SIW biosensor and the LOD is calculated as 213 cells/µL. Chemicals of various concentrations are loaded on the sensor/channels and sensor response is tuned.…”

Simultaneous Detection of Two Chemicals Using a TE20-Mode Substrate-Integrated Waveguide Resonator

“…In conventional RF resonators using a single channel for sensing, such as those presented in [ 7 , 28 , 34 , 47 ] (a comparison has been already presented in Table 3 ), if the channel is biased due to any reason (such as misalignment or fabrication error), which is a common situation when handling high-frequency circuits or stacked-layer devices in which microfluidics are attached as a separate layer, the sensing measurements may become unreliable. Considering a similar situation (channel biasing) in a dual-channel sensor, using one channel (liquid) as a reference and the other channel for sensing an analyte can provide more reliable detection, compared with using a single channel per sensor [ 50 , 51 ].…”

Planar Microwave Resonant Sensors: A Review and Recent Developments

“…This review paper focuses on microwave sensors, and particularly on planar sensors based on resonant elements for material characterization, including solids or liquids. Planar sensors are of special interest as their low-profile is compatible with many applications, where bulk sensors (e.g., cavity sensors or waveguide-based sensors [1,2], among others) may find a severe limitation, e.g., conformal sensors [3], wearable sensors [4], submersible sensors [5], integrated sensors [6], lab-on-a-chip sensors [7], microfluidic sensors [8][9][10][11], etc. On the other hand, despite the fact that non-resonant planar sensors operating at microwave frequencies have been reported [12][13][14], the combination of sensor size and performance (sensitivity) of resonant-type sensor is difficult to achieve with non-resonant methods.…”