Browsing by Subject "Flow measurement"

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Open Access
Bow tie shaped coplanar waveguide microwave resonators for single cell detection, flow rate measurements, and nanopore sensing of viruses
(2020-09) Seçme, Arda
Measurement sensitivity of different biosensing applications can be enhanced by using the microwave resonators. In the first application, microwave sensors based on bow tie shaped coplanar waveguide (CPW) resonator was designed to detect single cells in real-time. While the resonator was kept at its resonance frequency, cells/particles were made a pass through the sensing electrodes and their frequency shift statistics were obtained. For each cell, the geometrical size that is obtained from the optical microscope was correlated to the electrical volume of the cell which was measured by the microwave signals. A linear relationship was observed between the electrical and geometrical volume of a cell. Dispersion caused by the device geometry was elucidated using the standard sized polystyrene microparticles. To observe the single-cell dynamic, a target cell was trapped around the sensing region, and its microwave response was continuously recorded. Then cells were treated with dimethyl sulfoxide (DMSO), a chemical accelerating dehydration, and a decline in the resonance shifts by time was observed as the cell lost total content. Secondly, the same microwave design was patterned on a low-stress thin film membrane and used for flow rate measurements. When the flow is on, there were certain shapes continuously formed on the membrane and after a critical point pulsation of the membrane cause a shift in the resonance frequency. When the flow rate was increased, it was observed that these shapes formed faster so does frequency shifts in the resonance. Therefore, the effective flow rate could be correlated to the pulsation frequency of the membrane. Then, devices with different membrane size and different channel geometry were fabricated to span different flow rate values. As a secondary sensing mechanism, the flow was given from the reset condition where there was no flow. In this case, the amount of frequency shift was related to the flow rate and a monotonically increasing relation was obtained. As a next step, instead of liquid, the air was pressurized to measure the flow rate. Airflow measurements have become important during the COVID19 pandemic as the flow rate sensors are the most essential component of the ventilation machines. Using the secondary mechanism, frequency shifts induced by airflow were recorded and a linear relation was observed between the applied air pressure and frequency modulations. In the last application, the sensing electrodes were patterned down to hundreds of nanometer apart to detect nanoparticles and biological samples such as polystyrene nanoparticles or viruses. A nanopore having a diameter around 400 nm was drilled on the membrane using focused ion beam (FIB) and analytes were translocated using electrokinetic motion. Since the events would be quick in electrokinetic motion, data were collected with CompactRIO (cRIO), however, when the PLL was running, there were spikes in cRIO for this reason after the resonator was locked to zero degrees, LabVIEW was stopped. Yet, since the resonator has low quality factor (≈100), the phase of the resonator dwells around zero degrees and still sensitive to translocations through the pore. In the control run, there were no precipitous jumps, however, when the particles were added sudden jumps induced by the particles were recorded. Therefore, can be optimized and proposed as a biophysical sensor to characterize single viruses.
Open Access
Chaotic behavior of gas bubble in non-Newtonian fluid: A numerical study
(2013) Behnia, S.; Mobadersani F.; Yahyavi, M.; Rezavand, A.
In the present paper, the nonlinear behavior of bubble growth under the excitation of an acoustic pressure pulse in non-Newtonian fluid domain has been investigated. Due to the importance of the bubble in the medical applications such as drug, protein or gene delivery, blood is assumed to be the reference fluid. Effects of viscoelasticity term, Deborah number, amplitude and frequency of the acoustic pulse are studied. We have studied the dynamic behavior of the radial response of bubble using Lyapunov exponent spectra, bifurcation diagrams, time series and phase diagram. A period-doubling bifurcation structure is predicted to occur for certain values of the effects of parameters. The results show that by increasing the elasticity of the fluid, the growth phenomenon will be unstable. On the other hand, when the frequency of the external pulse increases the bubble growth experiences more stable condition. It is shown that the results are in good agreement with the previous studies. © 2013 Springer Science+Business Media Dordrecht.
Open Access
Effect of magnetic field on the radial pulsations of a gas bubble in a non-Newtonian fluid
(Elsevier Ltd, 2015) Behnia, S.; Mobadersani F.; Yahyavi, M.; Rezavand, A.; Hoesinpour, N.; Ezzat, A.
Dynamics of acoustically driven bubbles' radial oscillations in viscoelastic fluids are known as complex and uncontrollable phenomenon indicative of highly active nonlinear as well as chaotic behavior. In the present paper, the effect of magnetic fields on the non-linear behavior of bubble growth under the excitation of an acoustic pressure pulse in non-Newtonian fluid domain has been investigated. The constitutive equation [Upper-Convective Maxwell (UCM)] was used for modeling the rheological behaviors of the fluid. Due to the importance of the bubble in the medical applications such as drug, protein or gene delivery, blood is assumed to be the reference fluid. It was found that the magnetic field parameter (B) can be used for controlling the nonlinear radial oscillations of a spherical, acoustically forced gas bubble in nonlinear viscoelastic media. The relevance and importance of this control method to biomedical ultrasound applications were highlighted. We have studied the dynamic behavior of the radial response of the bubble before and after applying the magnetic field using Lyapunov exponent spectra, bifurcation diagrams and time series. A period-doubling bifurcation structure was predicted to occur for certain values of the parameters effects. Results indicated its strong impact on reducing the chaotic radial oscillations to regular ones. © 2015 Elsevier Ltd. All rights reserved.