Browsing by Subject "Microwave sensors"

Now showing 1 - 8 of 8

Open Access
Classification of dielectric microparticles by microwave impedance cytometry
(Cold Spring Harbor Laboratory, 2022-09-28) Hanay, M. Selim; Sarı, Burak; Tefek, Uzay
AbstractCoulter counters and impedance cytometry are commonly used for counting microscopic objects, such as cells and microparticles flowing in a liquid, as well as to obtain their size distribution. However, the ability of these techniques to provide simultaneous material information — via dielectric permittivity measurements — has been limited so far. The challenge stems from the fact that the signals generated by microparticles of identical size, but different material composition, are close to each other. The similarity in impedance signals arises because the material-dependent factor is determined mainly by the volume of aqueous solution displaced by the microparticles, rather than the microparticles themselves. To differentiate between materially distinct particles with similar geometry and size, another measurement mode needs to be implemented. Here, we describe a new microfluidics-based sensor that provides material classification between microparticles with similar sizes by integrating impedance cytometry with microwave resonator sensors on the same chip. While low-frequency impedance cytometry provides the geometric size of particles, the microwave sensor operating at three orders-of-magnitude higher frequency provides their electrical size. By combining these two measurements, the Clausius-Mossotti factors of microparticles can be calculated to serve as a differentiation parameter. In addition to distinguishing dielectric materials from cells and metals, we classified two different dielectric microparticles with similar sizes and electrical characteristics: polystyrene and soda lime glass, with 94% identification accuracy. The proposed technique can serve as an automated monitoring system for quality control of manufactured microparticles and facilitate environmental microplastic screening.
Open Access
High resolution dielectric characterization of single cells and microparticles using integrated microfluidic microwave sensors
(Institute of Electrical and Electronics Engineers, 2023-03-01) Seçme, Arda; Tefek, Uzay; Sarı, Burak; Pisheh, Hadi Sedaghat; Uslu, H. Dilara; Akbulut, Özge; Küçükoğlu, Berk; Erdogan, R. Tufan; Alhmoud, Hashim; Şahin, Özgür; Hanay, M. Selim
Microwave sensors can probe intrinsic material properties of analytes in a microfluidic channel at physiologically relevant ion concentrations. While microwave sensors have been used to detect single cells and microparticles in earlier studies, the synergistic use and comparative analysis of microwave sensors with optical microscopy for material classification and size tracking applications have been scarcely investigated so far. Here we combined microwave and optical sensing to differentiate microscale objects based on their dielectric properties. We designed and fabricated two types of planar sensor: a Coplanar Waveguide Resonator (CPW) and a Split-Ring Resonator (SRR). Both sensors possessed sensing electrodes with a narrow gap to detect single cells passing through a microfluidic channel integrated on the same chip. We also show that standalone microwave sensors can track the relative changes in cellular size in real-time. In sensing single 20-micron diameter polystyrene particles, Signal-to-Noise ratio values of approximately 100 for CPW and 70 for SRR sensors were obtained. These findings demonstrate that microwave sensing technology can serve as a complementary technique for single-cell biophysical experiments and microscale pollutant screening.
Open Access
Metamaterial Absorber Based Multifunctional Sensor Application
(Institute of Physics Publishing, 2017) Ozer Z.; Mamedov, Amirullah; Özbay, Ekmel
In this study metamaterial based (MA) absorber sensor, integrated with an X-band waveguide, is numerically and experimentally suggested for important application including pressure, density sensing and marble type detecting applications based on rectangular split ring resonator, sensor layer and absorber layer that measures of changing in the dielectric constant and/or the thickness of a sensor layer. Changing of physical, chemical or biological parameters in the sensor layer can be detected by measuring the resonant frequency shifting of metamaterial absorber based sensor. Suggested MA based absorber sensor can be used for medical, biological, agricultural and chemical detecting applications in microwave frequency band. We compare the simulation and experimentally obtained results from the fabricated sample which are good agreement. Simulation results show that the proposed structure can detect the changing of the refractive indexes of different materials via special resonance frequencies, thus it could be said that the MA-based sensors have high sensitivity. Additionally due to the simple and tiny structures it could be adapted to other electronic devices in different sizes. © Published under licence by IOP Publishing Ltd.
Embargo
Microwave resonant sensor integration with impedance cytometry in microfluidic platform for probing micro-scale dielectric permittivity
(2023-09) Tefek, Uzay
This thesis presents a novel multiphysical sensor that integrates low-frequency impedance cytometry with high-frequency microwave capacitance sensing. The characterization of microscale objects, including microparticles and cells, is essential in various scientific disciplines, such as biology, materials science, and environmental science. Accurate identification and classification of these microscale entities are critical for applications ranging from drug delivery optimization to environmental impact assessment, however, the current techniques fall short in terms of the rapidity and cost-effectiveness necessary for analyzing extensive populations. To address this challenge, our hybrid sensor combines low-frequency impedance cytometry and high-frequency microwave capacitance sensing for material characterization based on dielectric permittivity. This integration offers a rapid, cost-effective, and highly accurate method for identifying and characterizing microscale particles and cells. Experimental studies demonstrate the sensor’s efficacy, achieving remarkable signal-to-noise ratios. The sensor’s versatility ex-tends monitoring permittivity changes in single cells exposed to fixing agents offering valuable insights into cellular properties. In summary, this thesis introduces an innovative multiphysical sensor that advances microscale entity analysis, enabling rapid and precise identification and characterization.
Open Access
On-chip flow rate sensing via membrane deformation and bistability probed by microwave resonators
(Springer Link, 8-04-2023) Seçme, Arda; Pisheh, Hadi Sedaghat; Tefek, Uzay; Uslu, H. Dilara; Küçükoğlu, Berk; Alataş, Ceren; Kelleci, Mehmet; Hanay, Mehmet Selim
Precise monitoring of fluid flow rates constitutes an integral problem in various lab-on-a-chip applications. While off-chip flow sensors are commonly used, new sensing mechanisms are being investigated to address the needs of increasingly complex lab-on-a-chip platforms which require local and non-intrusive flow rate sensing. In this regard, the deformability of microfluidic components has recently attracted attention as an on-chip sensing mechanism. To develop an on-chip flow rate sensor, here we utilized the mechanical deformations of a 220 nm thick Silicon Nitride membrane integrated with the microfluidic channel. Applied pressure and fluid flow induce different modes of deformations on the membrane, which are electronically probed by an integrated microwave resonator. The flow changes the capacitance, and in turn resonance frequency, of the microwave resonator. By tracking the resonance frequency, liquid flow was probed with the device. In addition to responding to applied pressure by deflection, the membrane also exhibits periodic pulsation motion under fluid flow at a constant rate. The two separate mechanisms, deflection and pulsation, constitute sensing mechanisms for pressure and flow rate. Using the same device architecture, we also detected pressure-induced deformations by a gas to draw further insight into the sensing mechanism of the membrane. Flow rate measurements based on the deformation and instability of thin membranes demonstrate the transduction potential of microwave resonators for fluid–structure interactions at micro- and nanoscales.
Open Access
On-chip liquid and gas flow rate sensing via membrane deformation and bistability probed by microwave resonators
(Springer, 2022-11-15) Seçme, Arda; Pisheh, Hadi Sedaghat; Uslu, H. Dilara; Tefek, Uzay; Küçükoğlu, Berk; Alataş, Ceren; Kelleci, Mehmet; Hanay, M. Selim
Abstract Precise monitoring of fluid flow rates constitutes an integral problem in various lab-on-a-chip applications. While off-chip flow sensors are commonly used, new sensing mechanisms are being investigated to address the needs of increasingly complex lab-on-a-chip platforms which require local and non-intrusive flow rate sensing. In this regard, the deformability of microfluidic components has recently attracted attention as an on-chip sensing mechanism. To develop an on-chip flow rate sensor, here we utilized the mechanical deformations of a 220 nm thick Silicon Nitride membrane integrated with the microfluidic channel. Fluid flow induces deformations on the membrane, which is electronically probed by the changes in the capacitance and resonance frequency of an overlapping microwave resonator. By tracking the resonance frequency, both liquid and gas flows were probed with the same device architecture. For liquid flow experiments, a secondary sensing mechanism emerged when it was observed that steady liquid flow induces periodic deformations on the membrane. Here, the period of membrane deformation depends on the flow rate and can again be measured electronically by the microwave sensor. Flow rate measurements based on the deformation and instability of thin membranes demonstrate the transduction potential of microwave resonators for fluid-structure interactions at micro and nanoscales.
Open Access
Permittivity-based classification by the integration of impedance cytometry and microwave sensing
(IEEE - Institute of Electrical and Electronics Engineers, 2023-11-07) Tefek, Uzay; Sarı, B.; Alhmoud, Hashim; Hanay, Mehmet Selim
The direct determination of the permittivity of individual micro-objects has proven challenging due to the convoluting effect of their geometric size on capacitive signals (i.e., on the electric size of a particle). To overcome this challenge, we have developed a sensing platform to independently obtain both the geometric and electric size of organic and inorganic particles, by combining impedance cytometry and microwave resonant sensing in a microfluidic chip. This way the microwave signal is normalized to yield an intrinsic parameter that depends only on permittivity. The permittivity can then be used for material classification or single-cell interrogation.
Open Access
Simple and high-sensitivity dielectric constant measurement using a high-directivity microstrip coupled-line directional coupler
(IEEE, 2022-06-23) Rahimian Omam, Zahra; Nayyeri, Vahid; Javid-Hosseini, Sayyed-Hossein; Ramahi, Omar M.
Simple methods using a microstrip coupled-line directional coupler (CLDC) are presented for dielectric constant measurements. The material under test (MUT) is placed on the coupled-line section of the coupler, and either the coupler’s coupling ( |S31| ) or its isolation level ( |S41| ) is considered as the sensor’s response. Putting different MUTs on the microstrip line leads to a change in the effective dielectric constant of the structure and consequently causing a change in the coupling coefficient. In addition, since the isolation level of a microstrip coupled-line coupler depends on the phase velocity difference between the substrate and the medium above the signal strips, putting different MUTs on the line significantly changes the isolation level. This change is significantly greater than the change in |S21| level of a microstrip line when loaded with different MUTs. Validation of the method is presented through measurements for both solid and liquid MUTs.