Ali Abouei Mehrizi | University of Tehran (original) (raw)
Papers by Ali Abouei Mehrizi
2017 24th National and 2nd International Iranian Conference on Biomedical Engineering (ICBME)
Investigating the fabrication of a favorable scaffold is a continuing sconcern and an essential s... more Investigating the fabrication of a favorable scaffold is a continuing sconcern and an essential step within tissue engineering. An ideal scaffold should mimic the structure of extracellular matrix (ECM) which has considerable impacts on its function. To meet this demands, in this study, three-dimensional scaffolds by polylactic acid (PLA) polymer 10%, 13%, 15%, 17% and 20% (w/v) with a novel architecture produced by a wet-electrospinning process have been fabricated and compared with dry-electrospun scaffolds that have been developed for tissue engineering applications. In the wet-electrospinning method, an aqueous solution of sodium hydroxide (NaOH) (pH~13) has been used as the coagulation bath instead of the aluminum collector which is used in the dry method. Comparing with usual nanofiber non-woven PLA fabric prepared by a conventional electrospinning method, wet-electrospun spongiform PLA nanofiber scaffolds have low apparent density and high porosity. The porosity of the scaffolds has been examined in this two methods and their mechanical properties as well as their morphology are investigated. All in all, it is shown that the novel nanofiber fabrication system would be amazingly useful for the structure control of the nanofiber fabric.
One of the newest ways of surgery is known as Minimally Invasive Surgery (MIS), which in spite of... more One of the newest ways of surgery is known as Minimally Invasive Surgery (MIS), which in spite of its benefits, because of surgeon's tactile sensing omission, causes some problems with detection of arteries and their exact positions in tissue during a surgery. In this study, tactile detection of an artery in tissue has been modeled by finite element method. In this modeling, three 2D models of tissue have been created: tissue, tissue including a tumor, and tissue including an artery. After solving the three models with similar boundary conditions and loadings, the 2D tactile mappings and stress graphs for upper nodes of models, which have the role of transferring tactile data, have been explored. Comparing these results showed that stress graphs of upper nodes of tissue including an artery is time-dependent. However, for two other models it is constant. Then, the effect of variation of different parameters of the model on artery detection such as tissue thickness, artery diamete...
Applied and Computational Mechanics, 2015
Microfluidic flow focusing devices have been utilized for droplet generation on account of its su... more Microfluidic flow focusing devices have been utilized for droplet generation on account of its superior control over droplet size. Droplet based microfluidics addressed many scientific issues by providing a novel technological platform for applications such as biology, pharmaceutical industry, biomedical studies and drug delivery. This study numerically investigated the droplet generation process of an aqueous flow in oleic acid oil in a microfluidic flow focusing device. A conservative level set method is conducted to numerically model the droplet generation process. The post processing of the simulation results are done using Canny edge detection image processing method, which is a novel approach. Moreover, the results of the numerical simulation were compared to the experimental data provided by Ten et al. on the same device. This method showed a maximum average deviation from the experimental results of 14.6% and a minimum of 6.96%. Also, by means of altering water and oil flows...
2017 24th National and 2nd International Iranian Conference on Biomedical Engineering (ICBME)
Orthopedic field is one of the most important applications of biodegradable implants. In this stu... more Orthopedic field is one of the most important applications of biodegradable implants. In this study, an optimized design of biodegradable orthopedic screw was introduced and evaluated. This optimization was done in such a way that could be generalized for other screws. First of all, effective parameters of the screw were identified and range of them for optimum design was investigated. Then in order to simulate the degradation process and mechanical loading reaction numerically, COMSOL was applied. Also, design of experiments (DOE) using Taguchi method was used to study the effects of parameters on changes during degradation process. Afterwards, by the analysis of signal to noise ratio, the optimum design of the screw was selected with the aim of minimize degraded molecular weight percentage and von mises stress simultaneously. The ideal orthopedic screw was designed using optimized parameters, and after 8-weeks degradation, the minimum value of the degraded molecular weight percentage and von mises stress are reported as 60.854% and 0.882e7 N/m2, respectively. At last, using a linear relation between Young's modulus changes and logarithm of molecular weight changes, the manner of Young's modulus reduction was predicted.
arXiv: Medical Physics, 2018
In this study, palpating and rolling arteries with different physical properties and tactile dist... more In this study, palpating and rolling arteries with different physical properties and tactile distinction of them from each other, using finite element method, are presented. Five models have been created: healthy artery containing blood, axisymmetric stenotic artery containing blood, nonaxisymmetric stenotic artery containing blood, artery empty of blood, and filled artery. After solving these models, it was observed that the stress graph of the models included a time-dependent stress peak except for the last two models. The value of graphs peak and difference between their maximum and minimum stresses are considered as the criteria of distinction of the models.
2020 27th National and 5th International Iranian Conference on Biomedical Engineering (ICBME), 2020
In recent years, microfluidics has been used widely in various biomedical applications. Due to th... more In recent years, microfluidics has been used widely in various biomedical applications. Due to the multiple advantages derived from capillary microfluidics, such as simplicity, low-cost fabrication, and being fast plus accurate, it has emerged as an alternative to traditional diagnosis assays. Gaining accurate results in the biomedical tests within capillary microfluidic devices requires precise controlling of the fluid flow rate inside the channels, which can be regulated by embedded capillary micropump. Discovering suitable micropump design has always been one of the most technical barriers in the development of capillary microfluidic systems for point-of-care testing. In this study, COMSOL Multiphysics, which is a commercial computational fluid dynamics (CFD) package based on finite element method (FEM), is utilized to perform numerical simulations of the mentioned challenge. The study carried out in five different capillary micropump geometries, which are created by employing a ...
Nowadays, one of the main problems encountered in minimally invasive surgery and telesurgery is t... more Nowadays, one of the main problems encountered in minimally invasive surgery and telesurgery is the detection of arteries in tissue. In this study, for the first time, tactile detection of an artery in tissue and distinguishing it from the tumor has been modeled by finite element method. In this modeling, three 2D models of tissue have been created: tissue, tissue including a tumor, and tissue including an artery. After solving three models with similar boundary conditions and loadings, first, the 2D tactile mappings and stress graphs for upper nodes of models, which have the role of transferring tactile data, have been explored. Comparing these results, if stress values of nodes are equal and constant, tissue is without tumor or artery. In addition, it was concluded that if stress graph includes a peak, the tissue has a tumor or an artery and that the stress graph of tissue including artery is time-dependent in comparison with the tissue including the tumor.
Chapter 1. The Four Senses in Humans: Sight, Hearing, Smell, and Taste Chapter 2. The Sense of To... more Chapter 1. The Four Senses in Humans: Sight, Hearing, Smell, and Taste Chapter 2. The Sense of Touch Chapter 3. Introduction to Tactile Sensing and Tactile Sensors Chapter 4. Introduction to Tactile Sensing Technologies Chapter 5. Strain Gauge Sensors Chapter 6. Piezoelectric Sensors Chapter 7. Application of Tactile Sensing in Surgery Chapter 8. Tactile Image Information Chapter 9. Application and Recent Developments of Tactile Sensing in Tumor Detection Chapter 10. Determination of Mechanical Properties of Biological Tissues Including Stiffness and Hardness Chapter 11. Application of Tactile Sensing in Robotic Surgery Chapter 12. Haptics Application in Surgical Simulation Abbreviations Index
2020 27th National and 5th International Iranian Conference on Biomedical Engineering (ICBME), 2020
Calcium phosphate cements are one the best grafting materials in bone fracture repair. They are e... more Calcium phosphate cements are one the best grafting materials in bone fracture repair. They are easily shapeable, bioactive, and biocompatible. These group of materials have lower fracture toughness and compressive strength, due to their porosity. For enhancement of some mechanical properties and reducing porosity, they are combined with materials such as hydroxyapatite fibers. This combination makes it possible to control and increase elastic modulus and compressive strength. The shape and the orientation of fibers can affect these parameters. In this study, mechanical properties of calcium phosphate cement which is enhanced by three different shaped fibers of hydroxyapatite is investigated via FEM simulation. Ratio of the fibers added in this composite cement is 10 vol.% and they are in spherical, ellipsoidal, and polyhedral shapes. Three specimens have about same elastic modulus but compressive strengths of each specimen and the stress distribution among the fibers are different.
Journal of Micromechanics and Microengineering
In this study, we have proposed volume-preserving strategies to boost chaoticadvection and improv... more In this study, we have proposed volume-preserving strategies to boost chaoticadvection and improve the mixing efficiency of serpentine micromixers. The proposed strategies revolve around the point that the volume of the micromixer is kept constant during the manipulation. The first strategy involves the utilization of a nozzle-diffuser (ND) shaped microchannel. Using this, the velocity of the fluids fluctuates in an alternating pattern, leading to additional chaotic advection, a decrease in the mixing path, and an increase in the mixing index. The second strategy uses non-aligned inlets to generate swirl inducing effects at the microchannel entrance, where the collision of two fluids generates angular momentum in the flow, providing more chaotic advection. These strategies proved to be effective in boosting the mixing efficiency over wide ranges of Re in which 60% enhancement (from 20.53% to 80.31%) was achieved for Re of 30 by applying an ND shaped microchannel, and 20% enhancement (from 12.71% to 32.21%) was achieved for a critical Re of 15 by applying both of the strategies simultaneously.
International Journal of Biological Macromolecules
Frontiers in Bioengineering and Biotechnology
Electrospinning is a promising method to fabricate bioengineered scaffolds, thanks to utilizing v... more Electrospinning is a promising method to fabricate bioengineered scaffolds, thanks to utilizing various types of biopolymers, flexible structures, and also the diversity of output properties. Mechanical properties are one of the major components of scaffold design to fabricate an efficacious artificial substitute for the natural extracellular matrix. Additionally, fiber orientations, as one of the scaffold structural parameters, could play a crucial role in the application of fabricated fibrous scaffolds. In this study, gelatin was used as a highly biocompatible polymer in blend with cellulose acetate (CA), a polysaccharide, to enhance the achievable range of mechanical characteristics to fabricated fibrous electrospun scaffolds. By altering input variables, such as polymers concentration, weight ratio, and mandrel rotation speed, scaffolds with various mechanical and morphological properties could be achieved. As expected, the electrospun scaffold with a higher mandrel rotation spe...
Microfluidics and Nanofluidics
Planar micromixers with repetitive units have received substantial research interest since they a... more Planar micromixers with repetitive units have received substantial research interest since they allow low cost, lab-on-a-chip (LOC), and point-of-care (POC) systems to achieve a proper level of mixing for any given process. This paper presents an efficient planar micromixer that combines four types of mixing units, including convergent-divergent, circular, rhombic, and G-shaped micromixers. Their combinations and resulting effects on the mixing efficiency are numerically and experimentally investigated. A comprehensive Taguchi design of experiment method was used to reduce the number of the combinations from 1024 to only 16, among which a micromixer made of rhombic and G-shaped units readily showed a mixing efficiency beyond 80% over a wide range of inlet Reynolds numbers 0.001-0.3 and 35-65; meanwhile, a pressure drop as low as 12 kPa was reported. The velocity and concentration fields and their gradients within the nominated micromixer were analyzed, providing a better understanding of the mixing mechanism. These results offer design insights for further development of planar micromixers with repetitive unites for low-cost LOC and POC devices.
Langmuir
One of the challenges of using growth factors for tissue regeneration is to monitor their biodist... more One of the challenges of using growth factors for tissue regeneration is to monitor their biodistribuition and delivery to injured tissues with a minimally invasive detection. In the present study, tracking of human vascular endothelial growth factor (VEGF) was achieved by chemically linking it with photoluminescent carbon dots (CDs). Carbon dots were synthesized by the hydrothermal method and subsequently, conjugated with VEGF using carbodiimide coupling. ELISA and Western blot analysis revealed that VEGF-conjugated CDs preserve the binding affinity of VEGF to its antibod-ies. We also show that VEGF-conjugated CDs maintain the functionality of VEGF for tube formation and cell migration. The VEGF-conjugated CDs were also used for in vitro imaging of human umbilical vein endothelial cells. The results of this work suggest that cell-penetrating VEGF-conjugated CDs can be used for growth factor protein tracking in therapeutic and tissue engineering applications.
Carbohydrate Polymers
The field of cartilage tissue engineering has been evolved in the last decade and a myriad of sca... more The field of cartilage tissue engineering has been evolved in the last decade and a myriad of scaffolding biomaterials and bioactive agents have been proposed. Controlled release of growth factors encapsulated in the polymeric nanomaterials has been of interest notably for the repair of damaged articular cartilage. Here, we proposed an on-chip hydrodynamic flow focusing microfluidic approach for synthesis of alginate nanogels loaded with the transforming growth factor beta 3 (TGF-β3) through an ionic gelation method in order to achieve precise release profile of these bioactive agents during chondrogenic differentiation of mesenchymal stem cells (MSCs). Alginate nanogels with adjustable sizes were synthesized by fine-tuning the flow rate ratio (FRR) in the microfluidic device consisting of cross-junction microchannels. The result of present study showed that the proposed approach can be a promising tool to synthesize bioactive-loaded polymeric nanogels for applications in drug delivery and tissue engineering.
Polymer Science, Series A
Hydrogels are mainly structures formed from biopolymers and/or polyelectrolytes, and contain larg... more Hydrogels are mainly structures formed from biopolymers and/or polyelectrolytes, and contain large amounts of trapped water. Smart cellulose-based superabsorbent hydrogels are the new generation of scaffold which fabricated directly from native cellulose (including bacterial cellulose) via cellulose dissolution. Cellulose has many hydroxyl groups and can be used to prepare hydrogels with fascinating structures and properties. Cellulose hydrogels based on its derivatives, including methyl cellulose (MC), hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), and carboxymethyl cellulose (CMC) can be fabricated by various methods. On the basis of the cross-linking method, the hydrogels can be divided into chemical and physical gels. Physical gels are formed by molecular self-assembly through ionic or hydrogen bonds, while chemical gels are formed by covalent bonds. Composite smart hydrogels are prepared using cellulose in conjunction with other polymers through blending, formation of polyelectrolyte complexes, and interpenetrating polymer networks (IPNs) technology. According to type of superabsorbent cellulose-based hydrogels fabrication methods, there are many various techniques to evaluate quality of them. Briefly, some of these means generally used to assess the hydrogel are described as following. The obtained gel membranes are characterized by infrared spectroscopy, scanning electron microscopy, thermo gravimetric analysis, and mechanical tests in order to investigate the crosslinking occurrence and modifications of cellulose resulting from the synthetic process, morphology of the hydrogels, their thermal stability, and viscoelastic extensional properties, respectively. This review highlights the recent progress in smart cellulose-based superabsorbent hydrogel designs, fabrication approaches and characterization methods, leading to the development of cellulose based smart superabsorbent hydrogels.
Journal of Applied Fluid Mechanics
DNA is a molecule and assortment of fruitful information of organisms and a wide range of viruses... more DNA is a molecule and assortment of fruitful information of organisms and a wide range of viruses. Polymerase chain reaction (PCR) is a process used to amplify DNA strands in order to generate millions of them and extract the applicable information. Although conventional methods for PCR are flourishing to a certain extent, they have such major drawbacks as contamination, high material consumption, and low-speed function. By the combination of PCR devices with the microfluidic approach and integrating them with droplet generation technology, the mentioned problems can be eliminated. In this study, a novel two-step rapid-cycle dropletbased PCR (dPCR) device, considering the design of microchannel and heat transfer system, has been presented. First, numerous studies have been conducted to select the proper droplet generator for the integration of the droplet generation with the PCR device. Then, with the careful attention to the requirements of a PCR device, the geometry of different zones of the PCR device has been, meticulously, designed. In the next and last step, the heat transfer system for the designed zones of the PCR device has been planned. Afterward, results are examined carefully which indicate that in a cycle of PCR, they are not any major discrepancies between the designed dPCR and the ideal one-the one that is intended to be created.
Carbohydrate Polymers
Hyaluronic acid (HA), a naturally sourced polysaccharide, has shown remarkable effectiveness on w... more Hyaluronic acid (HA), a naturally sourced polysaccharide, has shown remarkable effectiveness on wound healing, but its low mechanical strength and instability limits its frequent application in this field. In order to minimize this shortcoming, hyaluronic acid based wound dressings were blended with functionalized ZIF-8, which not only provides high mechanical strength, but also introduces antibacterial properties and promotes fibroblast migration and proliferation. To analyze physiochemical and biological characteristics of prepared wound dressings, tests including DLS, XRD, FTIR as well as antibacterial and cell adhesion assays were carried out. Results indicated that HA film modification boosted the Young's modulus from 138 to 176 K Pa, and reduced the water contact angle from 37.4 to 27.7 proving enhancement in hydrophilicity. Ameliorated antibacterial properties and better cell adhesion were also observed. Suitable cell viability was observed in samples with FZIF-8, since released Zn ions maintained within a safe concentration range.
2017 24th National and 2nd International Iranian Conference on Biomedical Engineering (ICBME)
Investigating the fabrication of a favorable scaffold is a continuing sconcern and an essential s... more Investigating the fabrication of a favorable scaffold is a continuing sconcern and an essential step within tissue engineering. An ideal scaffold should mimic the structure of extracellular matrix (ECM) which has considerable impacts on its function. To meet this demands, in this study, three-dimensional scaffolds by polylactic acid (PLA) polymer 10%, 13%, 15%, 17% and 20% (w/v) with a novel architecture produced by a wet-electrospinning process have been fabricated and compared with dry-electrospun scaffolds that have been developed for tissue engineering applications. In the wet-electrospinning method, an aqueous solution of sodium hydroxide (NaOH) (pH~13) has been used as the coagulation bath instead of the aluminum collector which is used in the dry method. Comparing with usual nanofiber non-woven PLA fabric prepared by a conventional electrospinning method, wet-electrospun spongiform PLA nanofiber scaffolds have low apparent density and high porosity. The porosity of the scaffolds has been examined in this two methods and their mechanical properties as well as their morphology are investigated. All in all, it is shown that the novel nanofiber fabrication system would be amazingly useful for the structure control of the nanofiber fabric.
One of the newest ways of surgery is known as Minimally Invasive Surgery (MIS), which in spite of... more One of the newest ways of surgery is known as Minimally Invasive Surgery (MIS), which in spite of its benefits, because of surgeon's tactile sensing omission, causes some problems with detection of arteries and their exact positions in tissue during a surgery. In this study, tactile detection of an artery in tissue has been modeled by finite element method. In this modeling, three 2D models of tissue have been created: tissue, tissue including a tumor, and tissue including an artery. After solving the three models with similar boundary conditions and loadings, the 2D tactile mappings and stress graphs for upper nodes of models, which have the role of transferring tactile data, have been explored. Comparing these results showed that stress graphs of upper nodes of tissue including an artery is time-dependent. However, for two other models it is constant. Then, the effect of variation of different parameters of the model on artery detection such as tissue thickness, artery diamete...
Applied and Computational Mechanics, 2015
Microfluidic flow focusing devices have been utilized for droplet generation on account of its su... more Microfluidic flow focusing devices have been utilized for droplet generation on account of its superior control over droplet size. Droplet based microfluidics addressed many scientific issues by providing a novel technological platform for applications such as biology, pharmaceutical industry, biomedical studies and drug delivery. This study numerically investigated the droplet generation process of an aqueous flow in oleic acid oil in a microfluidic flow focusing device. A conservative level set method is conducted to numerically model the droplet generation process. The post processing of the simulation results are done using Canny edge detection image processing method, which is a novel approach. Moreover, the results of the numerical simulation were compared to the experimental data provided by Ten et al. on the same device. This method showed a maximum average deviation from the experimental results of 14.6% and a minimum of 6.96%. Also, by means of altering water and oil flows...
2017 24th National and 2nd International Iranian Conference on Biomedical Engineering (ICBME)
Orthopedic field is one of the most important applications of biodegradable implants. In this stu... more Orthopedic field is one of the most important applications of biodegradable implants. In this study, an optimized design of biodegradable orthopedic screw was introduced and evaluated. This optimization was done in such a way that could be generalized for other screws. First of all, effective parameters of the screw were identified and range of them for optimum design was investigated. Then in order to simulate the degradation process and mechanical loading reaction numerically, COMSOL was applied. Also, design of experiments (DOE) using Taguchi method was used to study the effects of parameters on changes during degradation process. Afterwards, by the analysis of signal to noise ratio, the optimum design of the screw was selected with the aim of minimize degraded molecular weight percentage and von mises stress simultaneously. The ideal orthopedic screw was designed using optimized parameters, and after 8-weeks degradation, the minimum value of the degraded molecular weight percentage and von mises stress are reported as 60.854% and 0.882e7 N/m2, respectively. At last, using a linear relation between Young's modulus changes and logarithm of molecular weight changes, the manner of Young's modulus reduction was predicted.
arXiv: Medical Physics, 2018
In this study, palpating and rolling arteries with different physical properties and tactile dist... more In this study, palpating and rolling arteries with different physical properties and tactile distinction of them from each other, using finite element method, are presented. Five models have been created: healthy artery containing blood, axisymmetric stenotic artery containing blood, nonaxisymmetric stenotic artery containing blood, artery empty of blood, and filled artery. After solving these models, it was observed that the stress graph of the models included a time-dependent stress peak except for the last two models. The value of graphs peak and difference between their maximum and minimum stresses are considered as the criteria of distinction of the models.
2020 27th National and 5th International Iranian Conference on Biomedical Engineering (ICBME), 2020
In recent years, microfluidics has been used widely in various biomedical applications. Due to th... more In recent years, microfluidics has been used widely in various biomedical applications. Due to the multiple advantages derived from capillary microfluidics, such as simplicity, low-cost fabrication, and being fast plus accurate, it has emerged as an alternative to traditional diagnosis assays. Gaining accurate results in the biomedical tests within capillary microfluidic devices requires precise controlling of the fluid flow rate inside the channels, which can be regulated by embedded capillary micropump. Discovering suitable micropump design has always been one of the most technical barriers in the development of capillary microfluidic systems for point-of-care testing. In this study, COMSOL Multiphysics, which is a commercial computational fluid dynamics (CFD) package based on finite element method (FEM), is utilized to perform numerical simulations of the mentioned challenge. The study carried out in five different capillary micropump geometries, which are created by employing a ...
Nowadays, one of the main problems encountered in minimally invasive surgery and telesurgery is t... more Nowadays, one of the main problems encountered in minimally invasive surgery and telesurgery is the detection of arteries in tissue. In this study, for the first time, tactile detection of an artery in tissue and distinguishing it from the tumor has been modeled by finite element method. In this modeling, three 2D models of tissue have been created: tissue, tissue including a tumor, and tissue including an artery. After solving three models with similar boundary conditions and loadings, first, the 2D tactile mappings and stress graphs for upper nodes of models, which have the role of transferring tactile data, have been explored. Comparing these results, if stress values of nodes are equal and constant, tissue is without tumor or artery. In addition, it was concluded that if stress graph includes a peak, the tissue has a tumor or an artery and that the stress graph of tissue including artery is time-dependent in comparison with the tissue including the tumor.
Chapter 1. The Four Senses in Humans: Sight, Hearing, Smell, and Taste Chapter 2. The Sense of To... more Chapter 1. The Four Senses in Humans: Sight, Hearing, Smell, and Taste Chapter 2. The Sense of Touch Chapter 3. Introduction to Tactile Sensing and Tactile Sensors Chapter 4. Introduction to Tactile Sensing Technologies Chapter 5. Strain Gauge Sensors Chapter 6. Piezoelectric Sensors Chapter 7. Application of Tactile Sensing in Surgery Chapter 8. Tactile Image Information Chapter 9. Application and Recent Developments of Tactile Sensing in Tumor Detection Chapter 10. Determination of Mechanical Properties of Biological Tissues Including Stiffness and Hardness Chapter 11. Application of Tactile Sensing in Robotic Surgery Chapter 12. Haptics Application in Surgical Simulation Abbreviations Index
2020 27th National and 5th International Iranian Conference on Biomedical Engineering (ICBME), 2020
Calcium phosphate cements are one the best grafting materials in bone fracture repair. They are e... more Calcium phosphate cements are one the best grafting materials in bone fracture repair. They are easily shapeable, bioactive, and biocompatible. These group of materials have lower fracture toughness and compressive strength, due to their porosity. For enhancement of some mechanical properties and reducing porosity, they are combined with materials such as hydroxyapatite fibers. This combination makes it possible to control and increase elastic modulus and compressive strength. The shape and the orientation of fibers can affect these parameters. In this study, mechanical properties of calcium phosphate cement which is enhanced by three different shaped fibers of hydroxyapatite is investigated via FEM simulation. Ratio of the fibers added in this composite cement is 10 vol.% and they are in spherical, ellipsoidal, and polyhedral shapes. Three specimens have about same elastic modulus but compressive strengths of each specimen and the stress distribution among the fibers are different.
Journal of Micromechanics and Microengineering
In this study, we have proposed volume-preserving strategies to boost chaoticadvection and improv... more In this study, we have proposed volume-preserving strategies to boost chaoticadvection and improve the mixing efficiency of serpentine micromixers. The proposed strategies revolve around the point that the volume of the micromixer is kept constant during the manipulation. The first strategy involves the utilization of a nozzle-diffuser (ND) shaped microchannel. Using this, the velocity of the fluids fluctuates in an alternating pattern, leading to additional chaotic advection, a decrease in the mixing path, and an increase in the mixing index. The second strategy uses non-aligned inlets to generate swirl inducing effects at the microchannel entrance, where the collision of two fluids generates angular momentum in the flow, providing more chaotic advection. These strategies proved to be effective in boosting the mixing efficiency over wide ranges of Re in which 60% enhancement (from 20.53% to 80.31%) was achieved for Re of 30 by applying an ND shaped microchannel, and 20% enhancement (from 12.71% to 32.21%) was achieved for a critical Re of 15 by applying both of the strategies simultaneously.
International Journal of Biological Macromolecules
Frontiers in Bioengineering and Biotechnology
Electrospinning is a promising method to fabricate bioengineered scaffolds, thanks to utilizing v... more Electrospinning is a promising method to fabricate bioengineered scaffolds, thanks to utilizing various types of biopolymers, flexible structures, and also the diversity of output properties. Mechanical properties are one of the major components of scaffold design to fabricate an efficacious artificial substitute for the natural extracellular matrix. Additionally, fiber orientations, as one of the scaffold structural parameters, could play a crucial role in the application of fabricated fibrous scaffolds. In this study, gelatin was used as a highly biocompatible polymer in blend with cellulose acetate (CA), a polysaccharide, to enhance the achievable range of mechanical characteristics to fabricated fibrous electrospun scaffolds. By altering input variables, such as polymers concentration, weight ratio, and mandrel rotation speed, scaffolds with various mechanical and morphological properties could be achieved. As expected, the electrospun scaffold with a higher mandrel rotation spe...
Microfluidics and Nanofluidics
Planar micromixers with repetitive units have received substantial research interest since they a... more Planar micromixers with repetitive units have received substantial research interest since they allow low cost, lab-on-a-chip (LOC), and point-of-care (POC) systems to achieve a proper level of mixing for any given process. This paper presents an efficient planar micromixer that combines four types of mixing units, including convergent-divergent, circular, rhombic, and G-shaped micromixers. Their combinations and resulting effects on the mixing efficiency are numerically and experimentally investigated. A comprehensive Taguchi design of experiment method was used to reduce the number of the combinations from 1024 to only 16, among which a micromixer made of rhombic and G-shaped units readily showed a mixing efficiency beyond 80% over a wide range of inlet Reynolds numbers 0.001-0.3 and 35-65; meanwhile, a pressure drop as low as 12 kPa was reported. The velocity and concentration fields and their gradients within the nominated micromixer were analyzed, providing a better understanding of the mixing mechanism. These results offer design insights for further development of planar micromixers with repetitive unites for low-cost LOC and POC devices.
Langmuir
One of the challenges of using growth factors for tissue regeneration is to monitor their biodist... more One of the challenges of using growth factors for tissue regeneration is to monitor their biodistribuition and delivery to injured tissues with a minimally invasive detection. In the present study, tracking of human vascular endothelial growth factor (VEGF) was achieved by chemically linking it with photoluminescent carbon dots (CDs). Carbon dots were synthesized by the hydrothermal method and subsequently, conjugated with VEGF using carbodiimide coupling. ELISA and Western blot analysis revealed that VEGF-conjugated CDs preserve the binding affinity of VEGF to its antibod-ies. We also show that VEGF-conjugated CDs maintain the functionality of VEGF for tube formation and cell migration. The VEGF-conjugated CDs were also used for in vitro imaging of human umbilical vein endothelial cells. The results of this work suggest that cell-penetrating VEGF-conjugated CDs can be used for growth factor protein tracking in therapeutic and tissue engineering applications.
Carbohydrate Polymers
The field of cartilage tissue engineering has been evolved in the last decade and a myriad of sca... more The field of cartilage tissue engineering has been evolved in the last decade and a myriad of scaffolding biomaterials and bioactive agents have been proposed. Controlled release of growth factors encapsulated in the polymeric nanomaterials has been of interest notably for the repair of damaged articular cartilage. Here, we proposed an on-chip hydrodynamic flow focusing microfluidic approach for synthesis of alginate nanogels loaded with the transforming growth factor beta 3 (TGF-β3) through an ionic gelation method in order to achieve precise release profile of these bioactive agents during chondrogenic differentiation of mesenchymal stem cells (MSCs). Alginate nanogels with adjustable sizes were synthesized by fine-tuning the flow rate ratio (FRR) in the microfluidic device consisting of cross-junction microchannels. The result of present study showed that the proposed approach can be a promising tool to synthesize bioactive-loaded polymeric nanogels for applications in drug delivery and tissue engineering.
Polymer Science, Series A
Hydrogels are mainly structures formed from biopolymers and/or polyelectrolytes, and contain larg... more Hydrogels are mainly structures formed from biopolymers and/or polyelectrolytes, and contain large amounts of trapped water. Smart cellulose-based superabsorbent hydrogels are the new generation of scaffold which fabricated directly from native cellulose (including bacterial cellulose) via cellulose dissolution. Cellulose has many hydroxyl groups and can be used to prepare hydrogels with fascinating structures and properties. Cellulose hydrogels based on its derivatives, including methyl cellulose (MC), hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), and carboxymethyl cellulose (CMC) can be fabricated by various methods. On the basis of the cross-linking method, the hydrogels can be divided into chemical and physical gels. Physical gels are formed by molecular self-assembly through ionic or hydrogen bonds, while chemical gels are formed by covalent bonds. Composite smart hydrogels are prepared using cellulose in conjunction with other polymers through blending, formation of polyelectrolyte complexes, and interpenetrating polymer networks (IPNs) technology. According to type of superabsorbent cellulose-based hydrogels fabrication methods, there are many various techniques to evaluate quality of them. Briefly, some of these means generally used to assess the hydrogel are described as following. The obtained gel membranes are characterized by infrared spectroscopy, scanning electron microscopy, thermo gravimetric analysis, and mechanical tests in order to investigate the crosslinking occurrence and modifications of cellulose resulting from the synthetic process, morphology of the hydrogels, their thermal stability, and viscoelastic extensional properties, respectively. This review highlights the recent progress in smart cellulose-based superabsorbent hydrogel designs, fabrication approaches and characterization methods, leading to the development of cellulose based smart superabsorbent hydrogels.
Journal of Applied Fluid Mechanics
DNA is a molecule and assortment of fruitful information of organisms and a wide range of viruses... more DNA is a molecule and assortment of fruitful information of organisms and a wide range of viruses. Polymerase chain reaction (PCR) is a process used to amplify DNA strands in order to generate millions of them and extract the applicable information. Although conventional methods for PCR are flourishing to a certain extent, they have such major drawbacks as contamination, high material consumption, and low-speed function. By the combination of PCR devices with the microfluidic approach and integrating them with droplet generation technology, the mentioned problems can be eliminated. In this study, a novel two-step rapid-cycle dropletbased PCR (dPCR) device, considering the design of microchannel and heat transfer system, has been presented. First, numerous studies have been conducted to select the proper droplet generator for the integration of the droplet generation with the PCR device. Then, with the careful attention to the requirements of a PCR device, the geometry of different zones of the PCR device has been, meticulously, designed. In the next and last step, the heat transfer system for the designed zones of the PCR device has been planned. Afterward, results are examined carefully which indicate that in a cycle of PCR, they are not any major discrepancies between the designed dPCR and the ideal one-the one that is intended to be created.
Carbohydrate Polymers
Hyaluronic acid (HA), a naturally sourced polysaccharide, has shown remarkable effectiveness on w... more Hyaluronic acid (HA), a naturally sourced polysaccharide, has shown remarkable effectiveness on wound healing, but its low mechanical strength and instability limits its frequent application in this field. In order to minimize this shortcoming, hyaluronic acid based wound dressings were blended with functionalized ZIF-8, which not only provides high mechanical strength, but also introduces antibacterial properties and promotes fibroblast migration and proliferation. To analyze physiochemical and biological characteristics of prepared wound dressings, tests including DLS, XRD, FTIR as well as antibacterial and cell adhesion assays were carried out. Results indicated that HA film modification boosted the Young's modulus from 138 to 176 K Pa, and reduced the water contact angle from 37.4 to 27.7 proving enhancement in hydrophilicity. Ameliorated antibacterial properties and better cell adhesion were also observed. Suitable cell viability was observed in samples with FZIF-8, since released Zn ions maintained within a safe concentration range.