Experimental and numerical study of elasto-inertial focusing in straight channels.

Elasto-inertial microfluidics has drawn significant attention in recent years due to its enhanced capabilities compared to pure inertial systems in control of small microparticles. Previous investigations have focused mainly on the applications of elasto-inertial sorting, rather than studying its fundamentals. This is because of the complexity of simulation and analysis, due to the presence of viscoelastic force. There have been some investigative efforts on the mechanisms of elasto-inertial focusing in straight channels; however, these studies were limited to simple rectangular channels and neglected the effects of geometry and flow rates on focusing positions. Herein, for the first time, we experimentally and numerically explore the effects of elasticity accompanying channel cross-sectional geometry and sample flow rates on the focusing phenomenon in elasto-inertial systems. The results reveal that increasing the aspect ratio weakens the elastic force more than inertial force, causing a transition from one focusing position to two. In addition, they show that increasing the angle of a channel corner causes the elastic force to push the particles more efficiently toward the center over a larger area of the channel cross section. Following on from this, we proposed a new complex straight channel which demonstrates a tighter focusing band compared to other channel geometries. Finally, we focused Saccharomyces cerevisiae cells (3-5 μm) in the complex channel to showcase its capability in focusing small-size particles. We believe that this research work improves the understanding of focusing mechanisms in viscoelastic solutions and provides useful insights into the design of elasto-inertial microfluidic devices

Development of a Biomimetic Semicircular Canal with MEMS Sensors to Restore Balance

© 2001-2012 IEEE. A third of adults over the age of 50 suffer from chronic impairment of balance, posture, and/or gaze stability due to partial or complete impairment of the sensory cells in the inner ear responsible for these functions. The consequences of impaired balance organ can be dizziness, social withdrawal, and acceleration of the further functional decline. Despite the significant progress in biomedical sensing technologies, current artificial vestibular systems fail to function in practical situations and in very low frequencies. Herein, we introduced a novel biomechanical device that closely mimics the human vestibular system. A microelectromechanical systems (MEMS) flow sensor was first developed to mimic the vestibular haircell sensors. The sensor was then embedded into a three-dimensional (3D) printed semicircular canal and tested at various angular accelerations in the frequency range from 0.5Hz to 1.5Hz. The miniaturized device embedded into a 3D printed model will respond to mechanical deflections and essentially restore the sense of balance in patients with vestibular dysfunctions. The experimental and simulation studies of semicircular canal presented in this work will pave the way for the development of balance sensory system, which could lead to the design of a low-cost and commercially viable medical device with significant health benefits and economic potential

3D Printing of Inertial Microfluidic Devices.

Inertial microfluidics has been broadly investigated, resulting in the development of various applications, mainly for particle or cell separation. Lateral migrations of these particles within a microchannel strictly depend on the channel design and its cross-section. Nonetheless, the fabrication of these microchannels is a continuous challenging issue for the microfluidic community, where the most studied channel cross-sections are limited to only rectangular and more recently trapezoidal microchannels. As a result, a huge amount of potential remains intact for other geometries with cross-sections difficult to fabricate with standard microfabrication techniques. In this study, by leveraging on benefits of additive manufacturing, we have proposed a new method for the fabrication of inertial microfluidic devices. In our proposed workflow, parts are first printed via a high-resolution DLP/SLA 3D printer and then bonded to a transparent PMMA sheet using a double-coated pressure-sensitive adhesive tape. Using this method, we have fabricated and tested a plethora of existing inertial microfluidic devices, whether in a single or multiplexed manner, such as straight, spiral, serpentine, curvilinear, and contraction-expansion arrays. Our characterizations using both particles and cells revealed that the produced chips could withstand a pressure up to 150 psi with minimum interference of the tape to the total functionality of the device and viability of cells. As a showcase of the versatility of our method, we have proposed a new spiral microchannel with right-angled triangular cross-section which is technically impossible to fabricate using the standard lithography. We are of the opinion that the method proposed in this study will open the door for more complex geometries with the bespoke passive internal flow. Furthermore, the proposed fabrication workflow can be adopted at the production level, enabling large-scale manufacturing of inertial microfluidic devices

Fabrication of unconventional inertial microfluidic channels using wax 3D printing.

Inertial microfluidics has emerged over the past decade as a powerful tool to accurately control cells and microparticles for diverse biological and medical applications. Many approaches have been proposed to date in order to increase the efficiency and accuracy of inertial microfluidic systems. However, the effects of channel cross-section and solution properties (Newtonian or non-Newtonian) have not been fully explored, primarily due to limitations in current microfabrication methods. In this study, we overcome many of these limitations using wax 3D printing technology and soft lithography through a novel workflow, which eliminates the need for the use of silicon lithography and polydimethylsiloxane (PDMS) bonding. We have shown that by adding dummy structures to reinforce the main channels, optimizing the gap between the dummy and main structures, and dissolving the support wax on a PDMS slab to minimize the additional handling steps, one can make various non-conventional microchannels. These substantially improve upon previous wax printed microfluidic devices where the working area falls into the realm of macrofluidics rather than microfluidics. Results revealed a surface roughness of 1.75 μm for the printed channels, which does not affect the performance of inertial microfluidic devices used in this study. Channels with complex cross-sections were fabricated and then analyzed to investigate the effects of viscoelasticity and superposition on the lateral migration of the particles. Finally, as a proof of concept, microcarriers were separated from human mesenchymal stem cells using an optimized channel with maximum cell-holding capacity, demonstrating the suitability of these microchannels in the bioprocessing industry

Coupling of CFD and semiempirical methods for designing three-phase condensate separator: case study and experimental validation

This study presents an approach to determine the dimensions of three-phase separators. First, we designed different vessel configurations based on the fluid properties of an Iranian gas condensate field. We then used a comprehensive computational fluid dynamic (CFD) method for analyzing the three-phase separation phenomena. For simulation purposes, the combined volume of fluid–discrete particle method (DPM) approach was used. The discrete random walk (DRW) model was used to include the effect of arbitrary particle movement due to variations caused by turbulence. In addition, the comparison of experimental and simulated results was generated using different turbulence models, i.e., standard k–ε, standard k–ω, and Reynolds stress model. The results of numerical calculations in terms of fluid profiles, separation performance and DPM particle behavior were used to choose the optimum vessel configuration. No difference between the dimensions of the optimum vessel and the existing separator was found. Also, simulation data were compared with experimental data pertaining to a similar existing separator. A reasonable agreement between the results of numerical calculation and experimental data was observed. These results showed that the used CFD model is well capable of investigating the performance of a three-phase separator

Effect of Frequency Aerobic Exercise on Expression of Bcl-2 and Bax Gene in Mice With Myocardial Infarction

Abstract   Background and Aim: Myocardial infarction (MI) is a permanent and irreversible cell death and death of the myocardium. Physical training reduces cardiac muscle apoptosis, but its molecular process is still unknown in response to activity and also the intensity of exercise. Exercise activity can be expected to prevent cell death by influencing the most important factors affecting the apoptosis process. Therefore, the aim of this study was to investigate the effect of aerobic exercise intensity on apoptosis in rats with myocardial infarction.   Methods: In this experimental study, 18 male Wistar rats with myocardial infarction were divided into three groups: High intensity periodic exercise (HIIT), Low intensity (LIIT) and Control group (without exercise). Bcl-2 and Bax cardiomyocyte concentrations were evaluated as the main markers of apoptosis by qRT-PCR method.   Results: Bcl-2 values ​​were significantly higher in the high intensity exercise group (HIIT) than in the control group (p = 0.077), in the low intensity periodic exercise group (LIIT) (p = 0.017) were more than the control group. Bax values ​​were significantly higher in the high intensity periodic exercise group (HIIT) (p = 0.019) than in the control group. While in the low intensity exercise group (LIIT), there was no significant increase compared to the control group (p = 0.98). BCL-2 values ​​in the low intensity periodic exercise group (LIIT) were higher than the high intensity periodic exercise group (HIIT) (p = 0.023). Bax index values ​​in the high intensity periodic exercise group (HIIT) were higher than the low intensity exercise group (1.91).   Conclusion: Periodic training was performed by expression of Bcl-2 and Bax gene and as a result of reduction of apoptosis in cardiomyocytes after myocardial infarction, which depends on the intensity of exercise. In addition, low intensity periodic exercises have a greater effect than high intensity periodic exercises. On this basis, it is recommended that attention be paid to intensive training in cardiac rehab.     &nbsp

Effects of sample rheology on the equilibrium position of particles and cells within a spiral microfluidic channel

Elasto-inertial migration in non-Newtonian fluids is a rapidly growing field with tremendous potentials for manipulating micron to submicron particles. Previous research attempts were mainly carried out in straight channels due to the complexity of particle migration, solution tuning, and data analysis in elasto-inertial microfluidics. Consequently, the combined effects of Dean drag force and solution rheology on coupled Dean drag elasto-inertial focusing phenomena have not been carefully analyzed. This study delved thoroughly into the combined effects of solution rheology and Dean drag force on elasto-inertial focusing of particles and cells within a spiral microchannel. Polyethylene oxide (PEO) of 1MDa, 2MDa, and 4MDa molecular weights were used to prepare 250, 500, and 1000 ppm non-Newtonian solutions to investigate the focusing behavior of particles and cells over a wide range of flow rates and solution rheologies. Dean coupled elasto-inertial effects were systematically investigated to demonstrate its potentials for position-adjustable and size-tunable particle and cell focusing phenomenon. Various cells and microbeads with diameters ranging from 1 to 17 μm were employed to carefully study the equilibrium position, focusing band, and migration behavior under different elastic, inertial, and Dean conditions. Following the focusing, cell viability, morphology, and growth rate were evaluated which showed cells remained undamaged from viscosity, shear rate, and chemical properties of PEO solutions. We are of the opinion that the current study can provide scientists with a better understanding of focusing phenomena in viscoelastic fluids within spiral microfluidic channels