Sharif Digital Repository

Droplet-based microfluidic logic gates have many applications in diagnostic assays and biosciences due to their automation and the ability to be cascaded. In spite of many bio-fluids, such as blood exhibit non-Newtonian characteristics, all the previous studies have been concerned with the Newtonian fluids. Moreover, none of the previous studies has investigated the operating regions of the logic gates. In this research, we consider a typical AND/OR logic gate with a power-law fluid. We study the effects of important parameters such as the power-law index, the droplet length, the capillary number, and the geometrical parameters of the microfluidic system on the operating regions of the... 

In the present study, the feasibility of electrospun polyethersolfone (PES) nanofibrous membrane as the solid substrate for microfluidic based immunoassays to enhance the density of immobilized antibody on the surface of membrane was assessed. Conversely, the efficacy of antibody immobilization was compared by two different strategies as 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC)/N-Hydroxysuccinimide (NHS) coupling chemistry and hydrophobic interaction. Compared to conventional immunoassays carried out in plates or gels, microfluidic based immunoassays grant a lot of advantages such as a consumption of little samples and reagents, shorter analysis time, and higher efficiency.... 

Incorporating numerical simulation with COMSOL Multiphysics, the aggregation and detection of superparamagnetic nanoparticles in microfluidic channels are investigated. Considering the physical specifications of the implemented microchannels, the parameters which determine the ability of the system for aggregation and detection of the particles are examined and simulated. Based on the simulation results, we propose a new approach for both capturing and detecting of the magnetic nanoparticles passing through microchannels  

In recent years, both tissue engineering and microfluidics have significantly contributed in engineering of in vitro skin substitutes to test the penetration of chemicals or to replace damaged skins. Organ-on-chip platforms have been recently inspired by the integration of microfluidics and biomaterials in order to develop physiologically relevant disease models. However, the application of organ-on-chip on the development of skin disease models is still limited and needs to be further developed. The impact of tissue engineering, biomaterials and microfluidic platforms on the development of skin grafts and biomimetic in vitro skin models is reviewed. The integration of tissue engineering and... 

The synthesis of plate-like silica particles, which are of importance for a variety of applications, are mainly based on the widely adopted method of the sol-gel reaction of silicon alkoxides in traditional batch-wise instrumentation. In this study, continuous-flow synthesis of amorphous plate-like silica particles is reported through combining droplet-based microfluidics and the sol-gel reaction of tetraethyl orthosilicate. The reaction was conducted at the surface of oil droplets, comprising tetraethyl orthosilicate (TEOS), suspended in acidic (HCl) water, resulting in silica particles on the surface of the droplets, leaving the device with outlet flow. The synthesized particles had... 

Since their introduction, paper-based microfluidic analytical devices (μPADs) have been ubiquitously utilized for different applications. The spontaneous imbibition of liquids in the paper-based devices that eliminates the requirement of an external pumping system has played a primary role in making paper an appropriate alternative for many other materials in the fabrication of microfluidic devices. Wax patterning is one of the most common methods to fabricate μPADs. Dynamics of the flow in channels with wax boundaries deviate from Washburn's law. Despite some research performed to model the effects of wax boundaries, some gaps remain in the presented models. A more general model is needed... 

Microfluidic concentration gradient generators (μCGGs) are indispensable parts of many emerging lab-on-a-chip platforms for biological studies and drug delivery applications. Most of the μCGGs reported in the literature can only generate the desired concentration gradients in a micron-sized sample (e.g., cells). As such, there is an unmet need to design a μCGG that can generate continuous concentration gradients of multi reagents (e.g., drugs) in a millimeter-sized sample (e.g., tissue). Herein, we report the proof-of-concept of this class of μCGG by combining a modified tree-like CGG with a micromixer. By conducting both experimental investigation and numerical analysis, we show that the... 

The integration of microfluidics with electrochemical analysis has resulted in the development of single miniaturized detection systems, which allows the precise control of sample volume with multianalyte detection capability in a cost- and time-effective manner. Microfluidic electrochemical sensing devices (MESDs) can potentially serve as precise sensing and monitoring systems for the detection of molecular markers in various detrimental diseases. MESDs offer several advantages, including (i) automated sample preparation and detection, (ii) low sample and reagent requirement, (iii) detection of multianalyte in a single run, (iv) multiplex analysis in a single integrated device, and (v)... 

The objective of this study is to design a novel and efficient portable lab-on-a-CD (LOCD) microfluidic device for separation of specific cells (target cells) using magnetic beads. In this study the results are shown for neutrophils as target cells. However, other kinds of target cells can be separated in a similar approach. The designed microfluidics can be utilized as a point of care system for neutrophil detection. This microfluidic system employs centrifugal and magnetic forces for separation. After model validation by the experimental data in the literature (that may be used as a design tool for developing centrifugo-magnetophoretic devices), two models are presented for separation of... 

Being the second cause of mortality across the globe, there is now a persistent effort to establish new cancer medication and therapies. Any accomplishment in treating cancers entails the existence of accurate identification systems empowering the early diagnosis. Recent studies indicate CTCs’ potential in cancer prognosis as well as therapy monitoring. The chief shortcoming with CTCs is that they are exceedingly rare cells in their clinically relevant concentration. Here, we simulated a microfluidic construct devised for immunomagnetic separation of the particles of interest from the background cells. This separation unit is integrated with a mixer subunit. The mixer is envisioned for... 

On-chip phase separation of multiphase microflows at the divergence point of Y-shaped microfluidic junctions is an effective way for integrating continuous microstructured devices. In this study, flow pattern maps of various solvent pairs based on the volumetric flow rates of both phases have been drawn experimentally and compared with numerical prediction to investigate the effective domain for which complete phase separation occurred. Furthermore, sufficient separation of aqueous and organic phases at the end of the microchannel was achieved by controlling the pressure difference at the liquid-liquid interface via loading back-pressure on the organic phase. A mathematical model based on... 

A cell spheroid is a three-dimensional (3D) aggregation of cells. Synthetic, in-vitro spheroids provide similar metabolism, proliferation, and species concentration gradients to those found in-vivo. For instance, cancer cell spheroids have been demonstrated to mimic in-vivo tumor microenvironments, and are thus suitable for in-vitro drug screening. The first part of this paper discusses the latest microfluidic designs for spheroid formation and culture, comparing their strategies and efficacy. The most recent microfluidic techniques for spheroid formation utilize emulsion, microwells, U-shaped microstructures, or digital microfluidics. The engineering aspects underpinning spheroid formation... 

Separation and lysis of RBCs play an important role in diagnosis of different diseases. Although they have been partially studied in several researches, a comprehensive study on integrating both separation and lysis units on a single chip has been seen rarely in the literature. Also, the factors related to the chemical lysis process have not been investigated in detail. In this study, we introduce a novel microfluidic channel design for sequential RBC's separation and lysis. For the separation part, an active method with an electric field was applied to the cells. Besides, a novel mixer was designed for mixing the cell solution and lysis reagent. In the lysis section, we used a mathematical... 

Microfluidic synthesis methods are among the most promising approaches for controlling the size and morphology of polymeric nanoparticles (NPs). In this work, for the first time, atomistic mechanisms involved in morphological changes of polybenzimidazole (PBI) NPs in microfluidic media are investigated. The multiscale molecular dynamic (MD) simulations are validated with the literature modeling and experimental data. A good agreement is obtained between the molecular modeling results and experimental data. The effects of mixing time, solvent type, dopant, and simulation box size at the molecular level are investigated. Mixing time has a positive impact on the morphology of the PBI NPs.... 

Droplet-based microfluidic systems have been employed to manipulate discrete fluid volumes with immiscible phases. Creating the fluid droplets at microscale has led to a paradigm shift in mixing, sorting, encapsulation, sensing, and designing high throughput devices for biomedical applications. Droplet microfluidics has opened many opportunities in microparticle synthesis, molecular detection, diagnostics, drug delivery, and cell biology. In the present review, we first introduce standard methods for droplet generation (i.e. passive and active methods) and discuss the latest examples of emulsification and particle synthesis approaches enabled by microfluidic platforms. Then, the applications... 

Centrifugal microfluidics or the Lab on a CD (LOCD) has developed vast applications in biomedical researches and analyses. Fluid mixing is an application of the LOCD. In this paper, multiple centrifugal micromixers were simulated. Various parameters were originally presumed to have an effect on mixing performance. These parameters include inlet angle, angular velocity, cross-sectional profile, perpendicular length ratio and the number of channels in series. They were each analyzed through simulations. It was gathered that the inlet angle does not significantly affect the mixing quality. Increasing angular velocity steadily increases mixing quality for all geometries. The vertical triangular... 

A telescoped approach was developed for the efficient synthesis of methoxybenzene through the generation of an unstable intermediate reagent, based on the Br-Li exchange reaction of p-bromoanisole and n-BuLi, followed by its reaction with water. In the first stage, p-methoxyphenyllithium was synthesized and consumed immediately in the second stage. For this purpose, an integrated glass microfluidic device was fabricated using laser ablation followed by the thermal fusion bonding method. The impact of various parameters, including solvent, reaction time, molar ratio, concentration of reagents, and flow rates were investigated to achieve the highest yield of the desired product, leading to an... 

Microfluidics has been becoming more and more popular over last two decades. The reason for this, is inherent features of microfluidics including low consumption of samples and reagents, high sensitivity, short analysis time, and low cost. As well as, centrifugal microfluidics as a subset of microfluidics has been able to prove itself as a helpful tool in analytic assays. The main application of centrifugal microfluidic devices is being used in point-of-care testing systems. Herein, we presented a microfluidic disc for measuring hemoglobin(Hb) concentration in the EDTA-anticoagulated venous blood using cyanmethemoglobin method. In this experiment, at first a hand-made standard solution was... 

The development of microfluidic hydrogels is an attractive method to generate continuous perfusion, induce vascularization, increase solute delivery, and ultimately improve cell viability. However, the transport processes in many in vitro studies still have not been realized completely. To address this problem, we have developed a microchanneled hydrogel with different collagen type I concentrations of 1, 2, and 3 wt% and assessed its physical properties and obtained diffusion coefficient of nutrient within the hydrogel. It is well known that microchannel geometry has critical role in maintaining stable perfusion rate. Therefore, in this study, a computational modeling was applied to...