Zahra Abbasi


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Real-Time Lead Detection Device Based on Nanomaterials Modified Microwave-Microfluidic Sensor
Weijia Cui, Ren Zhe, Zahra Abbasi, Yongxin Song, Carolyn L. Ren
Sensors and Actuators A: Physical, Volume 362

Lead contamination in drinking water has become an increasingly serious global risk because a small concentration of lead can cause serious health problems, particularly for children. It is critical to frequently monitor lead concentration in drinking water, which can be challenging when using traditional centralized systems. In this study, we present an inexpensive, portable detection system for point-of-care (POC) monitoring of lead concentration in drinking water. The sensing mechanism is based on the interaction between the water sample flowing through a microchannel and a planar microwave resonator-based sensor that is integrated with the microfluidic chip. The microwave sensor has a double-T structure with a gap in between through which the microchannel is aligned and can be coated with gold nanoparticles to enhance its sensing performance. For proof-of-concept, the sample under test (SUT) was a small volume of deionized (DI) water or tap water spiked with lead ions at different concentrations. Results show that the gold nanoparticle-coated microwave sensor presents a much higher sensitivity than bare sensors with a detectable frequency shift of 5 MHz for a Pb2+ solution with a concentration of 1 ppb. The success of the system for testing lead ions in typical tap water which contains many different mineral ions confirms its real-world application. To highlight the potential for POC applications, a low-cost, portable vector network analyzer is used to capture the frequency shift of the sensor. The developed method offers a promising approach for POC monitoring of lead contamination in drinking water impactful for environmental and public health protection.


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Crosstalk analysis and optimization in a compact microwave-microfluidic device towards simultaneous sensing and heating of individual droplets
Weijia Cui, Zahra Abbasi, Carolyn L. Ren
Journal of Micromechanics and Microengineering, Volume 32, Issue 9

Abstract Non-invasive contactless simultaneous sensing and heating of individual droplets would allow droplet microfluidics to empower a wide range of applications. However, it is challenging to realize simultaneous sensing and heating of individual droplets as the resonance frequency of the droplet fluid, which is decided by its permittivity, must be known so that energy is only supplied at this frequency for droplet heating with one resonator. To tailor the energy transfer in real-life heating applications, the droplet has to be sensed first to identify its corresponding resonance frequency, which is used to dynamically tune the frequency for supplying the required energy for heating this particular droplet. To achieve this goal, two resonators are needed, with one for sensing and one for heating. Integrating multiple resonators into one typical microfluidic device limits placement of the resonators to be as close as possible, which would raise the concern of crosstalk between them. The crosstalk would result in inaccurate sensing and heating. This study focuses on numerically and experimentally investigating the effect of influencing parameters on the crosstalk between two adjacent resonators with the ultimate goal of providing guidance for multiplexing the resonators in a typical microfluidic device. ANSYS HFSS is used to perform the electromagnetic analysis based on the finite element method. Experimental studies are conducted on a microfluidic chip integrated with two resonators to validate the numerical results. An optimal distance between two resonators is suggested, with the recommendation for the resonator size and heating power towards simultaneous sensing and heating of individual droplets.

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Passive Disposable Microwave Sensor for Online Microplastic Contamination Monitoring
Maziar Shafiei, Zahra Abbasi, Carolyn L. Ren
2022 IEEE/MTT-S International Microwave Symposium - IMS 2022

In this paper, non-contact microplastic concentration monitoring is enabled using a sensitivity-enhanced planar microwave sensor. The sensing platform is a tag-reader structure that consists of a dual-resonator tag and a passive microwave reader. The dual-tag structure is combined with a silicon reservoir as a sample container and is energized through the electromagnetic (EM) coupling with the reader. The extremely sensitive area of the tag resonators is exposed to the sample under the test; it creates an exceptional microplastic deposition monitoring with the concentration of the microplastic in the liquid under the test as low as 400K particles/L. The sensor monitors the deposition of microplastic particles in the mixed liquid in a real-time manner and reflects it as the frequency resonance variation in the transmission response.