Sharif Digital Repository

Isolation of rare cancer cells is one of the important and valuable stages of cancer research. Regarding the rarity of cancer cells in blood samples, it is important to invent an efficient separation device for cell enrichment. In this study, two centrifugal microfluidic devices were designed and fabricated for the isolation of rare cancer cells. The first design (passive plan) employs a contraction–expansion array (CEA) microchannel which is connected to a bifurcation region. This device is able to isolate the target cells through inertial effects and bifurcation law. The second design (hybrid plan) also utilizes a CEA microchannel, but instead of using the bifurcation region, it is... 

Cells docking inside microfluidic devices is effective in studying cell biology, cell-based biosensing, as well as drug screening. Furthermore, single cell and regularly cells docking inside the microstructure of microfluidic systems are advantageous in different analyses of single cells exposed to equal drug concentration and mechanical stimulus. In this study, we investigated bottom wall microgrooves with semicircular and rectangular geometries with different sizes which are suitable for single cell docking along the length of the microgroove in x-direction and numerous cells docking regularly in one line inside the microgroove in a 3D microchannel. We used computational fluid dynamics to... 

Cells docking inside microfluidic devices is effective in studying cell biology, cell-based biosensing, as well as drug screening. Furthermore, single cell and regularly cells docking inside the microstructure of microfluidic systems are advantageous in different analyses of single cells exposed to equal drug concentration and mechanical stimulus. In this study, we investigated bottom wall microgrooves with semicircular and rectangular geometries with different sizes which are suitable for single cell docking along the length of the microgroove in x-direction and numerous cells docking regularly in one line inside the microgroove in a 3D microchannel. We used computational fluid dynamics to... 

Bacterial populations are promising candidates for the development of the receiver and transmitter nanomachines for molecular communication (MC). A bacterial receiver is required to uptake the information molecules and produce the detectable molecules following a regulation mechanism. We have constructed a novel bacterial MC receiver using an inducible bacterial L-rhamnose-regulating operon. The proposed bacterial receiver produces green fluorescent protein (GFP) in response to the L-rhamnose information molecules following a quite fast regulation mechanism. To fabricate the receiver, the bacterial population has been transformed using a plasmid harboring L-rhamnose operon genes and gene... 

Researchers usually simplify their simulations by considering the Newtonian fluid assumption in microfluidic devices. However, it is essential to study the behavior of real non-Newtonian fluids in such systems. Moreover, using the external electric or magnetic fields in these systems can be very beneficial for manipulating the droplet size. This study considers the simulation of the process of non-Newtonian droplets’ formation under the influence of an external electric field. The novelty of this study is the use of a shear-thinning fluid as the droplet phase in this process, which has been less studied despite its numerous applications. The effects of an external electric field on this... 

Isolation and characterization of circulating tumor cells (CTCs) found in blood samples of cancer patients have been considered as a reliable source for cancer prognosis and diagnosis. A new continuous microfluidic platform has been designed in this investigation for simultaneous capture and characterization of CTCs based on their deformability. The deformability-based chip (D-Chip) consists of two sections of separation and characterization where slanted weirs with a gap of 7 μm were considered. Although sometimes CTCs and leukocytes have the same size, the deformability differs in such a way that can be exploited for enrichment purposes. MCF7 and MDA-MB-231 cell lines were used for the... 

Polymerase chain reaction (PCR) is a powerful tool for nucleic acid amplification and quantification. However, long thermocycling time is a major limitation of the commercial PCR devices in the point-of-care (POC). Herein, we have developed a rapid droplet-based photonic PCR (dpPCR) system, including a gold (Au) nanofilm-based microfluidic chip and a plasmonic photothermal cycler. The chip is fabricated by adding mineral oil to uncured polydimethylsiloxane (PDMS) to suppress droplet evaporation in PDMS microfluidic chips during PCR thermocycling. A PDMS to gold bonding technique using a double-sided adhesive tape is applied to enhance the bonding strength between the oil-added PDMS and the... 

Nucleic acid amplification using polymerase chain reaction (PCR) method has been widely used in different fields such as agricultural science, medicine, pathogen identification, and forensics to name a few. Today, it seems inevitable to have a robust, simple PCR system for diagnostics at the point-of-care (POC) level. Many photonic PCR systems have been proposed in the literature that benefit from plasmonic photothermal heating to achieve the common PCR thermal cycling. However, non-homogeneous temperature distribution is a challenge in some of them. In the present work, to achieve more efficient gene amplification, the effect of adding TiO2 nanoparticles has been investigated in a photonic... 

Electroactive-Polymers (EAPs) are one of the best soft $mu $ -actuators with great biomedical applications. Ionic ones (i-EAPs) have more promising features and have adequate potential for using in the active microfluidic devices. Here, as a case study, we have designed and fabricated a microfluidic micromixer using an i-EAP named Ionic Polymer-Metal Composite (IPMC). In microfluidics, active devices have more functionality but due to their required facilities are less effective for Point of Care Tests (POCTs). In the direction of solving this paradox, we should use some active components that they need minimum facilities. IPMC can be one of these components, hence by integrating the IPMC... 

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... 

Organ-on-a-chip technology tries to mimic the complexity of native tissues in vitro. Important progress has recently been made in using this technology to study the gut with and without microbiota. These in vitro models can serve as an alternative to animal models for studying physiology, pathology, and pharmacology. While these models have greater physiological relevance than two-dimensional (2D) cell systems in vitro, endocrine and immunological functions in gut-on-a-chip models are still poorly represented. Furthermore, the construction of complex models, in which different cell types and structures interact, remains a challenge. Generally, gut-on-a-chip models have the potential to... 

Magnetically actuated droplet manipulation offers a promising tool for biomedical and engineering applications, such as drug delivery, biochemistry, sample handling in lab-on-chip devices and tissue engineering. In this study, characteristics of an adjustable alternating magnetic field generated by a magnetic coil for droplet manipulation was investigated which enables more control on droplet transport, and it can be considered as a suitable alternative for moving magnets or an array of micro-coils. By adjusting the magnetic flux density, the duty cycle and applied magnetic frequency, the manipulation of water-based ferrofluid droplets with a bio-compatible surfactant for different volumes... 

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... 

Recently, microfluidic paper-based analytical devices (μPADs) have outstripped polymeric microfluidic devices in the ease of fabrication and simplicity. Surface tension-based fluid motion in the paper's porous structure has made the paper a suitable substrate for multiple biological assays by directing fluid into multiple assay zones. The widespread assumption in most works for modeling wicking in a paper is that the paper is a combination of capillaries with the same diameter equal to the effective pore diameter. Although assuming paper as a bundle of capillaries gives a good insight into pressure force that drives the fluid inside the paper, there are some difficulties using the effective... 

Electroporation is defined as cell membrane permeabilization under the application of electric fields. The mechanism of hydrophilic pore formation is not yet well understood. When cells are exposed to electric fields, electrical stresses act on their surfaces. These electrical stresses play a crucial role in cell membrane structural changes, which lead to cell permeabilization. These electrical stresses depend on the dielectric properties of the cell, buffer solution, and the applied electric field characteristics. In the current study, the effect of electric field frequency on the electrical stresses distribution on the cell surface and cell deformation is numerically and experimentally... 

Concentration gradient generators (CGGs) help biologists to perform large scale, fast and high-throughput experiments. This paper introduces a design tool called Tree-like Concentration gradient generator Design Tool (TCDT). The performance of this tool is validated both numerically and experimentally. Three CGGs were fabricated using three different fabrication methods and design parameters. The performance of these devices was examined using the measurement of fluorescent and dye intensity. The performance of the design tool for non-linear and multi-drug concentration gradient generations was investigated as well. In addition, a method was developed to investigate the multi-drug... 

Due to the importance of hydrogen as an effective antioxidant for its applications in therapy, this research reports the fabrication of a coupled microfluidic microbial electrochemical cell (MXC), including microfluidic microbial fuel cells (MFCs) and a microfluidic microbial electrolysis cell (MEC) series in order to perform it as a self-powered biohydrogen generator. Being able to be a platform of implantable medical devices, utilization a non-phatogenic strain of Escherichia coli as the biocatalyst in order to exploit the embodied energy from human blood and excrement and finally the use of cheap and facile materials (<$2 per device) are the exceptional features of the system. The... 

Herein, some (modified) paper–based substrates were prepared and utilized as extractive phases in a microfluidic device and their extraction performances examined for analytes with different polarities. Reagents including hexadecyltrimethoxysilane (HDTMS), phenyltrimethoxysilane (PTES), (3-aminopropyl) triethoxysilane (APTES) and 3–(2,3–epoxypropoxy) propyltrimethoxysilane (EPPTMOS) were implemented for the modification process. Due to the induction of different silane functional groups, it was anticipated to have various interactions for the tested analytes. Eventually, the prepared paper sheets were used as extractive phases for solid–phase extraction within a microfluidic system. The... 

Endothelial cell migration is a crucial step in the process of new blood vessel formation - a necessary process to maintain cell viability inside thick tissue constructs. Here, we report a new method for maintaining cell viability and inducing cell migration using a perfused microfluidic platform based on collagen gel and a gradient hydrogel sheet. Due to the helpful role of the extracellular matrix components in cell viability, we developed a hydrogel sheet from decellularized tissue (DT) of the bovine heart and chitosan (CS). The results showed that hydrogel sheets with an optimum weight ratio of CS/DT = 2 possess a porosity of around 75%, a mechanical strength of 23 kPa, and display cell... 

Microfluidic droplet generators excel in generating monodisperse micrometer-sized droplets and particles. However, the low throughput of conventional droplet generators hinders their clinical and industrial translation. Current approaches to parallelize microdevices are challenged by the two-dimensional nature of the standard fabrication methods. Here, we report the facile production of three-dimensionally (3D) parallelized microfluidic droplet generators consisting of stacked and radially multiplexed channel designs. Computational fluid dynamics simulations form the design basis for a microflow distributor that ensures similar flow rates through all droplet generators. Stereolithography is...