M. Taheri,
Volume 19, Issue 1 (1-2019)
Abstract
Critical force and time are the two important output parameters in nanomanipulation of different particles. Various input parameters affect the critical force and time, among which dimensional parameters and velocity can be considered the most important ones. To accurately calculate the critical forces and time of the manipulation requires careful analysis of the effect of various input parameters. One of the new methods in affecting the sensitivity analysis of input parameters on problems are statistical sensitivity analysis methods, one of the most accurate methods of which is the Sobol method. Previously, research on the influence of various parameters on the 2D manipulation has been done. In this paper, for the first time, using Sobol statistical sensitivity analysis method, effects of various dimensional parameters, including length of cantilever, width of cantilever, thickness of cantilever, height of tip, the speed in direction of the x and y-axes, radius of the particle, radius of the tip needle, and length of particle have been studied on 8 output parameters, including critical force of sliding along the x-axis, rolling around the x-axis, sliding along the y-axis, rolling around the y-axis, and critical time of sliding along the x-axis, rolling around the x-axis, sliding along the y-axis, and rolling around the y-axis in 3D manipulation. The final obtained results demonstrate that “cantilever thickness” and “cantilever length” are the most influential parameters on critical forces, and “tip height” and “cantilever thickness” are the most influential ones on critical times.
H. Ramezannejad Azarboni, H. Keshavarzpour ,
Volume 19, Issue 1 (1-2019)
Abstract
In this study, based on the nonlocal nonlinear Euler-Bernoulli beam model, the primary and superharmonic resonance of a single carbon nanotube (CNT) resting on a viscoelastic foundation under the magnetic axial loads and temperature as well as transverse harmonic forces was investigated. Using Galerkin approximation along with the trigonometric shape functions, the nonlinear partial differential governing equation is reduced to nonlinear ordinary differential equation. The frequency response of the single walled CNT is derived by implementing the multiple time scale method for the primary and superharmonic resonances. The effects of surface elasticity, change in temperature, magnetic field and the length-to-outer diameter aspect ratio on the frequency response of CNT in the cases of primary and superharmonic resonances were analyzed. The results show that the nonlinearity according to considered geometrical and mechanical parameters in this study, may cause unpleasant jumping phenomenon accompanied by unstable region in the frequency response. In addition to the surface elasticity, magnetic field, smaller temperature changes, as well as larger aspect ratio have positive effects on weakening the jumping phenomenon and extending the stability level of single walled CNT.
B. Zarei , S.h. Bathaee , M. Taheri, M. Momeni ,
Volume 19, Issue 1 (1-2019)
Abstract
Nanotechnology deals with objects and materials in nanometer scale and it is being expanded in the field of materials tools and systems. Nowadays, human knowledge in nanotechnology is going through a commercializing path in order to provide more services. Living creatures are built of cells with 10 μm size. Some nanoparticles application in biology and medicine include drug and gene delivery, tissue engineering, and tumor destruction with heat. These procedures, which are done with nanoparticles manipulation, have two specific phase in general; in phase one, the amount of critical force and time are calculated based on dimensional and peripheral parameters. Now, it is tried to calculate nanoparticles displacement and velocity during the process in the phase two of nanoparticles manipulation. Also, in this paper, nanoparticles displacement and velocity were investigated in two dimensional space, using three main friction model namely coulomb, Hk, and lugre in phase two of nanoparticles manipulation. According to the results of this project, maximum speed and displacement was obtained, using lugre friction model and the minimum amounts in coulomb model. Also, with particles radius increase, displacement and velocity were reduced; this effect is engendered even without considering friction factor. Correspondingly, considering accuracy and validity, the coulomb model was the least accurate model and lugre was the most accurate one and the HK model was placed between these two models.
S.m. Zareei, M. Jamshidian, Sh. Sepehrirahnama , S. Ziaei-Rad,
Volume 19, Issue 2 (2-2019)
Abstract
Acoustofluidics, the study of acoustics in microfluidic systems, is the basis for analyzing many laboratory applications including the separation of particles, particle sorting, cleaning, and mixing multiphase systems. In this research, a three-dimensional finite element model for particle motion under acoustic radiation force in acoustic microchannels is developed and the interaction of the incident waves with a suspended particle in microchannel is investigated. Using finite element method, the first-order fields due to an applied standing wave are initially calculated and, then, the acoustic radiation force is directly calculated from the second-order perturbation equations. The simulation results for radiation force are first verified against the analytical solution in the Rayleigh limit and, then, examined beyond this limit, for which there is no explicit analytical solution. In addition, the quasi-static motion of a particle under the influence of an applied acoustic standing wave in microchannel is simulated. For simulating particle motion, the acoustic stress on particle surface is calculated and transferred as an input to the laminar flow equations. Then, the drag force is estimated based on the shear stress due to the flow around the particle. The simulation results demonstrate that the particle velocity depends on its position with respect to the wave node at the center of the microchannel. As the particle approaches to the center of microchannel, its velocity decreases until it stops at the center of microchannel.
N. Sheikhizad , M. Kalteh ,
Volume 19, Issue 3 (3-2019)
Abstract
In the present study, the electroosmotic and pressure driven flow of nanofluid in a microchannel with homogeneous surface potential is investigated by using the Poisson-Boltzmann equation and the flow field is assumed to be two-dimensional, laminar, incompressible, and steady. Distribution of nanoparticles in the base fluid is assumed to be homogeneous; therefore the nanofluid flow is modeled as a single phase. The thermal conductivity of the nanofluid is modeled by using the Patel model to account for temperature dependency. In order to validate the numerical solution, the results are compared with available analytical solutions and the comparison shows a good match with the results. Then, the effects of different parameters such as ion molar percentage, volume fraction, and nanoparticles’ diameter on the flow field and heat transfer are examined. The results show that by fixing the electric field and increasing the pressure gradient, the local Nusselt number will decrease, and by fixing the pressure gradient and enhancing the electric field, the Nusselt number increases. The average Nusselt number increases about 45, 35 and 25% while nanoparticles’ diameters are 100, 110 and 120nm, respectively. For Γ=0.05, the average Nusselt number increases 10% while ion concentration changes from 10-4 to 10-2. Furthermore, the direction and magnitude of velocity and concavity of the velocity profile can be controlled by choosing a suitable phase angle between electrical and pressure driven flow parameters.
S.a. Ashrafnia , M. Jamshidian ,
Volume 19, Issue 4 (4-2019)
Abstract
The unique characteristics of nanostructures are mainly due to their large surface to volume ratio. One of the most important quantities in investigating the surface properties of materials is the surface energy. Therefore, calculating the surface energy is necessary for the proper understanding of the behavior and properties of nanostructured materials. The present study investigates the size-dependent surface energy of crystalline nanoparticles and nanocavities of aluminum, silver, copper, and iron. For this purpose, spherical nanoparticles and nanocavities with different radiuses are modeled by molecular dynamics simulations and their surface energy is obtained. The simulation results demonstrate that for nanoparticles and nanocavities with sufficiently small radiuses in the range of a few nanometers, the surface energy depends on the size of the nanostructure. For spherical nanoparticles, the surface energy increases with increasing nanoparticle radius, while for the spherical nanocavities, the surface energy decreases by increasing nanocavity radius. Also, the surface energy variation with size is more intense for nanocavities in comparison with nanoparticles. By increasing the radius, the surface energy of nanoparticles and nanocavities approaches to an asymptotical value, which is the surface energy of a crystalline flat surface or the Gibbs surface energy for the crystallographic surface orientation with the maximum surface energy.
M. Arvahi , S.gh. Masoudi , A. Mohammadi ,
Volume 19, Issue 4 (4-2019)
Abstract
Microfluidic chips in the last two decades have had significant advances in the analysis of interfacial tension phenomenon due to their many advantages. To analyze interfacial tension phenomena, droplet flow in microchannels can be used. In this study, water-n-hexane interfacial tension in the presence of surface-active agents was measured, using microfluidic tensiometry. For this purpose, a glass microfluidic flow-focusing junction was fabricated for generating n-hexane droplets within an aqueous phase. The dependence of droplet size on the concentration of surfactants has been investigated. A theoretical equation was developed, considering force balance on the droplet generation in the microfluidic device, giving a relation between the interfacial tension and the generated droplet sizes. By standardizing the microfluidic chips with the aid of a system, whose interfacial tension is known (hexane normal and tween 20 in distilled water), interfacial tension can be measured with measuring the size of produced droplets for other systems that can form droplets in the microchannel. In this study, the microfluidic device and the relation were employed to measure the interfacial tension in the presence of either of sodium dodecyl sulphate (SDS) or Cetyl trimethylammonium bromide (CTAB) surfactants. It was found that the measured interfacial tensions deviate less than 10% compared to those measured with a commercially available ring method.
M. Molavian Jazi, M. Ghayour , S. Ziaei-Rad , E. Maani,
Volume 19, Issue 4 (4-2019)
Abstract
The atomic force microscope (AFM) determines the topography of surfaces in nano scale based on the changes in the exited micro-cantilever’s dynamic characteristics. Therefore, it is essential to simulate and predict more accurately the dynamic behavior of cantilever beams for use in design and fabrication of AFM. Based on the experimental observations, in contrast to the classic theory, the normalized stiffness of structures is not constant with the reduction of dimensions in micro and nano scales. This change, which can be either softness or stiffness, results in size-dependent behavior, non-classic continuum theories. This paper studies the effect of size on the dynamic behavior of AFM based on modified couple stress theory, and compares the results with those obtained from classic theory. The nonlinear partial differential governing equation of the system is derived, considering intermolecular and hydrodynamic forces, based on the modified couple stress theory. By applying Galerkin projection method, partial differential equations are transformed into ordinary equations and the discrete system is extracted. It is shown that considering size effect leads to enlargement of expected working domain of AFM, and also predicted amplitude and frequency of oscillations decreases and increases, respectively. Moreover, two theories predict different start point of bi-stability region. Solution approach is verified by comparing the results with two degrees-of-freedom model and analogue equations method. Furthermore, effect of hydrodynamic forces of fluid on dynamic behaviour of AFM is investigated.
B. Saeedi, R. Vatankhah,
Volume 19, Issue 6 (6-2019)
Abstract
In this article, the sensitivity and resonant frequency of the atomic force microscope made of functionally graded materials is investigated by couple stress theory (MCST). In MCST, the size effect of the system is taking into account by means of the material length scale parameter.
is made of a mixture of metal and ceramic with properties varying through the thickness following a simple In this work, due to the kinematic energy and potential energy of
, the governing equations of motion and corresponding boundary conditions are derived on the basis of Hamilton principle by considering Euler-Bernoulli beam theory. Based on the results, it is clear that when the contact stiffness increases, the sensitivity of the system decreases, and resonant frequency increases. Moreover, when the thickness comes approximately close to material length scale parameter, the difference between MCST and classical continuum mechanic becomes significant. Furthermore, in low contact stiffness, increasing the power reduces the sensitivity of
, while in high contact stiffness, increasing the power
increases the sensitivity of the system. Results also show that at each value of contact stiffness, as ceramic volume fraction increases the resonant frequency will be increased, too.
F. Mollaei, P. Aliparast, A. Naghash,
Volume 19, Issue 10 (10-2019)
Abstract
Adsorption simulation of vancomycin antibiotic is done using molecular dynamics. The simulation results show the adsorption behavior of vancomycin on a functionalized biosensor. Regarding the importance of vancomycin, its molecular function is simulated using multiscale discipline. Adsorption to a single assembly monolayer is considered according to vancomycin’s in-vivo function. A selected biosensor is a non-symmetrically functionalized microcantilever which undergoes deformation as a result of changes in surface tension regarding functionalized surface. Multiscale simulations implemented to calculate microcantilever deformation. Molecular models in a vacuum and aquatic media are taken into account. Energy parameters related to surface tension is studied versus the distance of target molecules to the surface of the biosensor. To calculate the distance between receptor molecules in single assembly monolayer, an algorithm is proposed based on experimental results.
E. Akrami Nia, H. Ekhteraei Toussi,
Volume 19, Issue 10 (10-2019)
Abstract
Microbeams are one of the most important members of microelectromechanical systems (MEMS) which contrast of electrical and mechanical forces in them cause pull-in instability. One of the proposed mechanisms for controlling this instability and enlarging the stable range of system are initially curved microbeams. Despite studying various pull-in instability in straight elastic or viscoelastic microbeams, the instability of curved microbeams has been investigated only within the range of elastic behavior. Therefore in the present study, assuming a clamped-clamped viscoelastic initially curved microbeam, the effect of viscoelastic behavior on the instabilities called snap-through and pull-in, was investigated. The viscoelastic behavior was simulated by the standard anelastic linear solid model. The governing differential equation was obtained based on the modified couple stress theory and by use of Hamilton’s pull-in instability principle. By using the Galerkin method, the governing equation was converted to a nonlinear ordinary differential equation and solved by MATLAB sofware. The structure behaviors are compared in two extreme situations before and after the viscoelastic relaxation by drawing diagrams. The results show when the time of structure relaxation increases, viscoelastic behavior causes more decreasing in instabilities voltage, but its effect on the position of instability will depend on the axial load. In this way, in the presence of tensile load, viscoelastic behavior increases the snap-through position and decreases the pull-in position, but in the presence of compressive load, snap-through occurs at smaller deflections and pull-in occurs at larger deflections.
H. Naderi, H. Elmkhah, Y. Mazaheri,
Volume 19, Issue 12 (12-2019)
Abstract
In this research, nanostructured TiAlN coatings were applied on HSS substrate using cathodic arc evaporation method (CAE) in the different duty cycle values. Then the effect of duty cycle on the coating surface properties including surface morphology and structure, coating thickness and mechanical behavior of nanostructured coatings were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the surface coatings. Also, micro indentation and adhesion test were utilized to evaluate the mechanical behavior. The results show that by changing the duty cycle, the macro-particles size and amount change which is effective on the roughness and morphology of the coatings. It is attributed to the electrical charge of macro-particles that are produced in the process which can be influenced by the structure. Also, the changes in grain size depend on the changes of duty cycle value. Furthermore, the mechanical properties of the coatings are affected by altering the duty cycle related to the deposition mechanism. The hardness value of TiAlN coatings increases from 3168 HV to 3817 HV when the duty cycle increases from 25% to 50%. But whit an increase in duty cycle from 50% to 75%, hardness reduced to 3582 HV. Consequently, it can be possible to find an optimum duty cycle value to achieve the best mechanical properties. Also, the minimum friction coefficient (0.44) and the minimum wear rate were determined for the TiAlN coating with the duty cycle of 75%, which it can be attributed to better smoothness and higher density of the coating.
I. Ghoytasi, O. Rahmani,
Volume 19, Issue 12 (12-2019)
Abstract
In this paper, the effects of unified temperature loading and Winkler-Pasternak elastic foundation on the vibration of functionally graded curved nanobeam have been studied. The proposed model is based on the modified couple stress theory and the Timoshenko beam model. The continuous distribution of material along the thickness of functionally graded curved nanobeam is achieved by changing the gradient index in the volume fraction. The governing equations and related boundary conditions are obtained using the Hamilton principle. By analyzing the quantitative and qualitative results in the tables and figures, influences of geometrical and thermo-physical parameters such as gradient index, aspect ratio, unified temperature difference, the ratio of thickness to length scale parameter and arc angle of functionally graded curved nanobeam on the natural frequency for different vibration mode have been interpreted. There is an excellent agreement between the present results and the results of the previous works. Applied temperature loading increases the sensitivity of the natural frequency to the changes in the aforementioned parameters and also increases the range of its changes. Also, applying the Pasternak elastic foundation changes the behavior of the natural frequency to the temperature changes.
Alireza Barani, Peiman Mosaddegh, Shaghayegh Haghjooy Javanmard, Shahrokh Sepehrirahnama,
Volume 21, Issue 10 (10-2021)
Abstract
These days, investigation on using acoustofluidic microchannels in separation of microparticles and cells is under consideration. Working under optimum efficiency, these microchannels should be designed and manufactured truly. In this work, a new methodology for designing and manufacturing of acoustofluidic microchannels are explained. Then, a metallic microchannel with 2-nodes of pressure wave based on this method was developed. For mass production purpose, a low cost and reliable method which is CNC micromachining is used. Also, to conduct the heat generated by the wave, this microchannel was made out of aluminum and then polishing technique is applied. Then, the performance of this microchannel in agglomerating of human blood cells and BT-20 breast cancer cells to nodal lines was experimentally studied. The results showed that the applied design and manufacturing technique are suitable. Although some tests were performed to find temperature rise of microchannel due to damping effect, it was found that true design method and also using metals with high thermal conductivity can prevent the temperature increase to the point beyond which living cells will be hurt.
Moein Taheri, Mahdi Mirzaluo,
Volume 22, Issue 1 (12-2021)
Abstract
Mutations in DNA and the development of mutated genes that are inherited or acquired during a personchr('39')s lifetime can cause cancer. This type of disease causes the loss of normal control of cell growth and proliferation. Breast cancer, with its prevalence in both men and women and the higher incidence of women in the female population, is one of the most important cancers in the medical community. Appearance changes in the breast, the presence of a lump, and discharge and bleeding from the nipple are signs of breast cancer. Targeted treatment of this disease reduces the complications of treatment methods. Also, recognizing the mechanical properties of the cell, such as the Youngchr('39')s modulus, and examining the changes caused by cancer in these properties will make treatment more efficient and help the pharmaceutical sciences. For this purpose, in this paper, the MCF-10 breast cell has been studied using atomic force microscopy and nanomanipulation method. Atomic force microscope is one of the efficient tools in the structural studies of biological particles with the possibility of producing images of soft tissues under different environmental conditions and in a non-destructive manner. Chung, chen and brake contact are the models used in the simulation. Finally, with the simulations performed, the Young modulus of 1200 Pa is considered for this cell. Also, considering the comparisons made with experimental work, the chen contact model has been introduced as the optimal model for extracting cellular properties.
Saman Mohammadnabi, Khosrow Rahmani,
Volume 22, Issue 4 (3-2022)
Abstract
In this paper, a new model for estimation of the electrical conductivity of polymer carbon nanotube (CNT) nanocomposites based on the conventional power-law model and Halpin-Tsai formulation has been proposed. Halpin-Tsai model was originally presented to calculate the tensile modulus of composites, which can be modified for estimation of the electrical conductivity by replacing the electrical parameters. The nature of “b” exponent in power-law model is defined according to CNT dimensions, CNT electrical conductivity and the interphase thickness and also the impacts of these parameters on the “b” and the electrical conductivity of nanocomposite are taken into consideration. The developed model interprets that the electrical conductivity of polymer-CNT nanocomposite increases as the concentration, length and electrical conductivity of CNT and the interphase thickness increase. Furthermore, reduction in CNT diameter and waviness results in growth of nanocomposite electrical conductivity. In order to validate the developed model, nanocomposite samples with different volume fractions were produced by solid-state technique of the melt-blending method. The results of calculations and experimental procedure show good agreement.
Mehdi Karimi Firouzjaei, Hassan Moslemi Naeini, Mohammad Mehdi Kasaei, Mohammad Javad Mirnia,
Volume 22, Issue 8 (8-2022)
Abstract
The deformation behavior of the material in micro-forming processes is different from macro-scale due to the size effect. The size effect in micro-scale appears due to few grains in the deformation region and causes the material behavior to be affected by the thickness and grain size of the sheet. Because of this, conventional constitutive models are not suitable for predicting the material behavior in micro-forming processes. In this paper, a new constitutive model based on the Swift equation and considering size effect in micro-scale is presented to describe the strain-hardening behavior of the stainless steel 304 foil. Comparison of flow stress curves of specimens with different grain sizes showed that the prediction of material flow stress with the new constitutive model is improved compared to the existing model, especially at high strains, so that the average and maximum error of the new model is less than one-third and less than half of the conventional model error, respectively. Finite element simulation of the micro-tensile test was performed using the new constitutive model to investigate the size effect on the deformation behavior of the specimens. The new constitutive model was verified by comparing the results of experimental tests and finite element simulation of sheets with different grain sizes. Also, the results revealed that the estimation of the forming force using the new constitutive model is done with higher accuracy than the conventional and existing model for sheets with different grain sizes and high strain ranges.
Hamed Kavand, Javad Koohsorkhi, Reza Askari Moghaddam,
Volume 23, Issue 1 (12-2022)
Abstract
The electrical properties of nanostructured piezoelectric materials have attracted the attention of many researchers in the last decade. These features are used in piezoelectric micro-sensors. Mechanical propulsion is usually the result of contact between a piezoelectric surface and a foreign object. In this paper, the effect of mechanical propulsion using an air wave (sound) or vacuum on a silicon diaphragm is investigated. The local stresses created on the diaphragm due to the impact of an air wave have a significant effect on the peak-to-peak voltage of the piezoelectric sensor, which can be measured by measuring changes in this parameter. To investigate this, a micromachined diaphragm of silicon was examined and it was found that fabricating a piezoelectric sensor on a thin and patterned diaphragm could increase the peak-to-peak voltage by about 1.3 times. Detection of these stresses using piezoelectric material layered on the thin and formable diaphragm can act as a piezoelectric microphone or a barometer that the presence of microstructures on the diaphragm will increase their sensitivity.
Seyed Mohammad Akhavan Alavi, Rahmatollah Ghajar,
Volume 24, Issue 1 (12-2023)
Abstract
In this article, the determination of the mechanical properties of a micro-cellular auxetic structure is investigated. This lattice structure consists of hexagonal cells, whose cell-wall dimensions are on a micro-scale. First, using modified strain gradient theory (MSGT) and energy method, the mechanical properties of the micro-cellular auxetic structure are analytically obtained. Then for validation, Young's modulus of a micro-cellular auxetic structure is derived by tensile test and compared with theoretical results. The comparison of analytical and experimental results shows good agreement. A nanosecond laser cutting machine is used to fabricate the microcellular auxetic structure, and the ISO 6892-1 standard is used to perform tensile tests. The results show that the modified strain gradient theory plays an important role in determining the mechanical properties of micro-cellular auxetic structures. In some cases, the results of this theory are more than 100% different from the classical theory. In addition, it can be seen that by changing the dimensional parameters of the micro-cells, the mechanical properties of the auxetic structure can be tunable. For example, by reducing the magnitude of the angle of the cell wall, Young's modulus in the X 1 direction increases, and Young's modulus in the X 2 direction and the shear modulus of the structure decrease
Hassan Nemati Garetapeh, Majid Rajabi,
Volume 24, Issue 6 (5-2024)
Abstract
Objective: Advances in microelectromechanical (MEMS) technologies over the past few decades have contributed to the rapid development of a wide range of microfluidic devices with different functionalities. Fluids are driven through microfluidic systems, therefore, in the current research, it is intended to parametrically investigate the effects of the main parameters, namely length, width and angle of attack of valves, piezoelectric length and applied voltage. Method: The approach of the present research is applied and analytical-experimental with numerical simulations where the tensile force is calculated using COMSOL Multiphysics software and the equations are calculated using the fully coupled algorithm in COMSOL Multiphysics. Findings: The results of the present research show that the main parameters significantly affect the performance of the designed micro pump. So that the applied voltage is 400 volts, the angle of attack is 45 degrees and the width of the valves is 6 micrometers, respectively for the piezoelectric length of 4, 2 and 5 mm, the flow rate is 6. 0.6, 9.6 and 16.6 microliters per minute are obtained. For valve widths of 6 and 8 micrometers, optimal attack angles of 60 and 65 degrees, the corresponding flow rates are 11.11 and 5.9 microliters per minute, respectively. Conclusion: Based on the results of the present research and the investigation of the behavior of the micropump and its output flow rate changes in different working conditions, as the length of the valves increases, the flow rate provided increases. Finally, there is a favorable condition for the width and angle of attack of the valves. This optimal width does not depend on the flow speed.
