A Microfluidic-Integrated SIW Lab-on-Substrate Sensor for Microliter Liquid Characterization

Abstract

Abstract-A novel microfluidic-integrated microwave sensor with potential application in microliter-volume biological/biomedical liquid sample characterization and quantification is presented in this paper. The sensor is designed based on the resonance method, providing the best sensing accuracy, and implemented by using a substrate-integratedwaveguide (SIW) structure combining with a rectangular slot antenna operating at 10 GHz. The device can perform accurate characterization of various liquid materials from very low to high loss, demonstrated by measurement of deionized (DI) water and methanol liquid mixtures. The measured relative permittivity, which is the real part of complex permittivity, ranges from 8.58 to 66.12, which is simply limited by the choice of test materials available in our laboratory, not any other technical considerations of the sensor. The fabricated sensor prototype requires a very small liquid volume of less than 7 µl, while still offering an overall accuracy of better than 3 %, as compared to the commercial and other published works. Key advantages of the proposed sensor are that it combines 1.) a very low-profile planar and miniaturized structure sensing microliter liquid volume; 2.) ease of design and fabrication, which makes it cost-effective to manufacture and 3.) noninvasive and contactless measurements. Moreover, since the microfluidic subsystem can potentially be detached from the SIW microwave sensor and, afterward, replaced by a new microfluidic component, the sensor can be reused with no life-cycle limitation and without degrading any figure of merit.

Microfluidic Biosensor Based on Microwave Substrate-Integrated Waveguide Cavity Resonator

“…Our proposed biosensor is also compared with RF MEMS bio/chemical sensors as given in Table 3. These sensors showed frequency shifts in the range of 10-40 MHz [41][42][43][44]. Another MEMS-based RF biosensor is developed to detect glucose levels in human serum, and it showed a frequency shift of 160 MHz [13].…”

Waveguide Dispersion Tailoring by Using Embedded Impedance Surfaces

“…The SIW resonators, with a compact size and a high Q factor, have been proposed to make microwave sensors for detecting complex permittivity inside the SIW. For instance, the device can be made by integrating a SIW with a liquid/air-based microfluidic channel [41][42][43]. In this context, the large and uniform electric field around ENZ frequencies has been proposed to make versatile waveguide-based permittivity sensors [44,45].…”

Liquids electrical characterization sensor using a hybrid SIW resonant cavity

“…The SIW technology allows designing high frequency planar structures operating in TE propagation modes using the theory and techniques of rectangular waveguides, and it provides an easy integration with microwave planar circuits . This technology has been employed to design liquids characterization sensors due to its benefits, such as low losses and low‐cost fabrication. As other examples, filters and power dividers can also be designed using the SIW technology.…”