Browsing by Author "Majidi, Negar"

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Blood clotting time measurement using a miniaturized high-frequency ultrasound sensor
(IEEE, 2023) Sobhani, M. R.; Majidi, Negar; Yaralıoğlu, Göksen Göksenin; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin; Majidi, Negar
This paper demonstrates a novel blood coagulation time measurement methodology that requires as low as 1 microliter of whole blood. The blood sample is placed on the top surface of a fused quartz plate where an ultrasonic transducer is fabricated on the bottom surface. The location of the blood sample is aligned with the transducer; therefore, the reflected acoustic waves from the blood/quartz interface are captured and converted to electrical signals by the transducer. The transducer is made of an 8 μm thick zinc oxide (ZnO) thin film that operates at 400 MHz. The acoustic impedance of blood changes due to the coagulation process. This affects the reflection coefficient and amplitude of the reflected waves from the blood/quartz interface. Thus, the blood coagulation time is determined by monitoring the amplitude of reflected acoustic waves. In the experiments, whole blood was used without any sample preparation. The method was tested using citrated blood with calcium chloride and activated partial thromboplastin (aPTT) reagents. We observed that aPTT coagulation times lengthened from 25 sec. to 47 sec. with the addition of heparin. The proposed method has the potential to be used in a disposable low-cost portable coagulation time measurement cartridge for patient self-testing.
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Blood coagulation time measurement using a 1μL of whole blood on a TE mode BAW resonator
(IEEE, 2018-12-20) Majidi, Negar; Sobhani, M. R.; Yaralıoğlu, Göksen Göksenin; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin; Majidi, Negar
This paper presents a possible way to blood coagulation time measurement using a TE (Thickness Extensions) mode BAW (Bulk Acoustic Wave) resonator which requires as low as 1 micro-liter of whole blood. The blood sample is placed on the top surface of a glass plate where a compressional ultrasonic transducer is fabricated on the bottom surface. The transducer is made of 8 μm thick zinc oxide (ZnO) thin film that has a thickness resonance frequency around 400 MHz. The transducer generates compressional (longitudinal) acoustic wave inside the piezoelectric thin film and glass substrate. The acoustic waves are mostly reflected and trapped inside the device from both sides of it; 1) the glass/liquid (blood) interface, and 2) the transducer/air interface. Most of the acoustic waves are reflected from the second interface because of the higher impedance mismatch, while the reflections from the first boundary are related to impedance (mechanical properties) of the liquid sample or blood. The acoustic impedance of blood changes due to the coagulation process. This affects the reflection coefficient and amplitude of the reflected waves from the blood/glass interface. Thus, the overall acoustic energy trapped inside the bulk film changes over the time which consequently affects the resonator parameters. The blood coagulation time was determined by monitoring the amplitude of the reflected sinusoidal acoustic waves at 400 MHz in the previous work using the same device. However, in this paper we demonstrate the resonance frequency shifts obtained by numerical modeling and practical measurements for a few liquid samples with different mechanical properties. The proposed method has a potential to be used in a low-cost portable coagulation time measurement cartridge which requires only 1μL of whole blood without centrifuging. A simple resonator can be implemented for tracking the resonating frequency to further reduce the size and cost of the device, to make it more suitable for patient self-testing applications.
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Blood coagulation time measurements using 400 MHz thickness mode resonator
(2018-08) Majidi, Negar; Yaralıoğlu, Göksenin; Yaralıoğlu, Göksenin; Uğurdağ, Hasan Fatih; Bozkurt, A.; Department of Electrical and Electronics Engineering; Majidi, Negar
This thesis presents a novel blood coagulation time measurement methodology which requires as low as 1 L of whole blood. The method performs measurements using whole blood without plasma separation. In this regard, the whole blood sample is placed on the top surface of a fused quartz plate (glass substrate) where an ultrasonic transducer (operating in thickness mode) is fabricated on the bottom surface. The transducer utilizes a short burst of 400 MHz compressional acoustic waves along the thickness of glass substrate. The location of the blood sample is aligned with the transducer; therefore, the re ected acoustic waves from the blood/quartz interface are captured and converted to electrical signals by the transducer. A Mason modeling of the transducer in frequency domain was expressed to show the changes of resonance frequency of the transducer for di erent samples, like air, water, and blood, alongside with a numerical modeling to show amplitude of acoustic waves propagating inside the transducer in time domain. The acoustic impedance of the blood changes due to the coagulation process. This a ects the re ection coe cient and amplitude of the re ected waves from the blood/quartz interface. A theoretical model was developed to show dependency of the acoustic waves amplitude to the re ection coe cient. Thus, the blood coagulation time was determined by monitoring the re ected acoustic waves amplitude. The transducer was made of 8 m thick of sputtered Zinc Oxide (ZnO) thin- lm that is operating at approximately 400 MHz TE (Thickness Extensional) mode. In the experiments, whole blood sample was used without any preparation. The method was tested using citrated blood with calcium chloride and activated partial thromboplastin (aPTT) reagents. We observed that aPTT coagulation times lengthen from 25 sec. to 47 sec. with the addition of heparin. The proposed method has a potential to be used in a disposable low cost portable coagulation time measurement cartridge for patient self-testing. The measurements were performed by collecting the amplitude of the re ected waves versus the time at speci c frequency (400 MHz); however, another possible way could be using a simple oscillator and a digital counter to track the resonance frequency and quality factor of the transducer versus the time. This will further reduce the cost and size of the proposed method. Nevertheless, this transducer has a potential to be used for characterizing liquid samples parameters like viscosity, if it is operated in frequency domain and the input impedance is being tracked. This could be used for the applications where the lower volume of an expensive drug or chemical to be tested, is mostly desired.
Open Access
Design and comparison of 4 types of dual resonance proximity coupled microstrip patch antennas
(The Applied Computational Electromagnetics Society, 2018-10) Majidi, Negar; Sobhani, M. R.; Kılıç, B.; İmeci, M.; Güngör, O. S.; İmeci, Ş. T.; Majidi, Negar
In this paper there are four different shapes of proximity patch antennas (straight, trimmed, trapezoid and ribbon). The minimum input match achieved with the straight proximity patch antenna as -39.68 dB. The maximum gain is achieved with the ribbon proximity patch antenna as 12.1 dB. Simulation and measurement results are presented. There is a perfect match with simulated and measured gain. The antenna is first demonstrated example of working with four different geometries, having satisfactory gain and input match.
Open Access
Design and implementation of a quad element patch antenna at 5.8 GHz
(The Applied Computational Electromagnetics Society, 2018-10) Sobhani, M. R.; Majidi, Negar; İmeci, Ş. T.; Majidi, Negar
This paper presents simulation and experimental verification of a quad microstrip patch antenna that operates at 5.8 GHz. Sonnet antenna design software was used to simulate the performance of the antenna. To reduce the design's complexity and the computational load, the antenna and the feeding lines were simulated separately. An optimization was done for each subpart to get the optimum desired results. Finally, all the subparts were merged and the final structure was simulated to check the performance. A prototype of the antenna was fabricated on a double-sided PCB substrate (relative permittivity=10.2, thickness=1.28 mm) using a PCB milling machine. The S11 of -14 dB and -18.8 dB and maximum gain of 6.2 dB and 4.2 dB were obtained, from the simulation and experimental measurements, respectively.
Metadata only
Design of a quad element patch antenna at 5.8 GHz
(IEEE, 2018) Majidi, Negar; Yaralıoğlu, Göksen Göksenin; Sobhani, M. R.; Imeci, T.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin; Majidi, Negar
This paper presents simulation and experimental verification of a quad microstrip patch antenna that operates at 5.8 GHz. Sonnet antenna design software was used to simulate the performance of the antenna. To reduce the design's complexity and the computational load, the antenna and the feeding lines were simulated separately. An optimization was done for each subpart to get the optimum desired results. Finally, all the subparts were merged and the final structure was simulated to check the performance. A prototype of the antenna was fabricated on a double sided PCB substrate (relative permittivity=10.2, thickness=1.28 mm) using a PCB milling machine. The s 11 of -14 dB and -18.8 dB and maximum gain of 6.2 dB and 4.2 dB were obtained, from the simulation and experimental measurements, respectively.
Metadata only
Dual resonance proximity coupled patch antenna
(IEEE, 2018-05-24) Kılıç, B.; İmeci, T.; Güngör, O. S.; İmeci, M.; Majidi, Negar; Sobhani, M. R.; Majidi, Negar
In this paper there are four different shape of proximity patch antennas (straight, trimmed, trapezoid and ribbon). The minimum input match achieved with the straight proximity patch antenna as -39.68 dB. The maximum gain is achieved with the ribbon proximity patch antenna as 12.1 dB. Simulation and measurement results are presented. There is a perfect match with simulated and measured gain. The antenna is first demonstrated example of working with four different geometries, having satisfactory gain and input match.