Sharif Digital Repository

The advent of nanopore-based sensors based on resitive pulse sensing gave rise to a remarkable breakthrough in the detection and characterization of nanoscale species. The sensors can detect the species’concentration, size, and charge using the resistive pulse characteristics. Some strong correlations have been reported between the resitive pulse characteristics and the particle’s geometrical and physical properties. These correlations are commonly used to obtain information about the particles in commercial devices and research setups. The correlations, however, do not consider the simultaneous effect of influential factors such as particle shape, charge, and off-axis translocation, which... 

Resistive pulse sensing (RPS) has proved to be a viable method for detection and characterization of micro and nano particles. This method works based on ionic current variation inside nanopores. Modern fabrication methods have introduced different nanopore geometries for resistive pulse sensors therefore studing the effects of geometry on sensing performance of nanaopores is important. Numerical simulation has been used to study a wide variation of nanopore’s geometry configurations and study the physics behind this phenomena. Based on the results, numerical simulation could be used as a fast and easy tool for size determination for nanopore. To compare the sensing performance of different... 

This study explores the significance of microfluidics, with a specific focus on the crucial role of droplet microfluidics. A novel microfluidic droplet generator is introduced in this study, employing a centrifuge-based approach. The generator features 2500 micropores on a single membrane, facilitating the production of over 50,000 droplets per second. An extensive investigation into various parameters, including centrifuge speed and micropore size, was conducted to assess their impact on the coefficient of variation in the final droplets. Remarkably, the experimentation resulted in achieving a coefficient of variation below 15 percent. Furthermore, the platform was utilized for synthesizing... 

The aim of this research is to design and optimize integrated microelectrodes on a chip for in-situ acid production and to investigate and utilize the capabilities of machine learning, particularly the reinforcement learning branch and genetic algorithms, in optimizing them with the goal of maximizing the number of electrodes on the chip, while ensuring that each operates independently. Initially, to validate and demonstrate the effectiveness of reinforcement learning using the DDQN algorithm, an agent was trained to optimize the geometric shape of an airfoil with the objective of maximizing the lift-to-drag ratio, showing that the agent can improve this ratio by over 100% in some cases.... 

The resistive pulse sensing (RPS) method based on the Coulter principle is a powerful method for particle counting and sizing in electrolyte solutions. This method involves measuring a current pulse that is produced as a particle transits a small channel, or pore. Throughout its development the technique has been expanded from detection of biological cells to counting nanoparticles and viruses, and even registering individual molecules, e.g., nucleotides in nucleic acids. This technique combined with microfluidic or nanofluidic systems shows great potential for various bioanalytical applications. An increasing number of production methods have been reported to make apertures, which have been... 

In this research, the ability of artificial intelligence to improve the biosensor performance of a microfluidic system has been investigated. Coulter counter is a microfluidic system that measures the concentration of particles in a fluid using signals obtained from a biosensor. The method of this system is called " Resistive Pulse Sensing (RPS)" method. The pulses in the Coulter counter signals are affected by the number, shape, size and speed of particles passing through the orifice. The pulse of two particles of the same size and different shape in these systems are very similar and this makes it difficult for an operator to distinguish the type of particle. Another disadvantage of... 

In recent years, significant attention has been given to methods for measuring micrometer and nanometer biological and synthetic particles using microfluidic systems. One such method is resistive pulse sensing, which is used to detect and count particles as well as determining their surface charge. This technique is based on Coulter's principle. When a micropore is placed in an electrolyte solution containing the target particles, a drop in electric current occurs as the particles pass through the pore. Electrodes on either side of the micropore allow for the analysis of the pulses generated by the particles. Tunable resistive pulse sensing enables the adjustment of the pore size, allowing... 

In this work a new innovative microfluidic system for the selection of motile sperms was developed. The novel aspect of this work is based on the fact the motile sperms follow microchannel walls. Immotile sperms are not able to follow curved paths and therefore their movement toward the outlet gets hindered and most of them could not reach to the outlet. But motile sperms, moving alongside the microchannel walls, reach to the outlet and get separated from the immotile ones. After designing, 3 microfluidic chips having curved microchannels with curvature radius of 150, 300 and 600 micrometer and one with a straight microchannel were fabricated using photolithography and soft lithography.... 

Droplet microfluidic platform generates monodisperse droplets in a desired size through immiscible multiphase flows inside microchannels. Droplets are individual reactor and can be used for bio(chemical) analyses. Also, for materials fabrication, droplet microfluidics offers a versatile platform for generation of nano- or micro-sized particles and microcapsules that are widely used in drug delivery. In addition to the monodispersity, high-throughput generation is also necessary in many applications. Therefore, droplets must be formed in stable regimes (dripping and squeezing) in the highest possible frequency. In this study, the flow-focusing geometry, which is the most common geometry in... 

The growing demand for diagnostic tools with enhanced analytical characteristics in terms of sensitivity, selectivity, and low response time has encouraged researchers to conduct their research towards the development of point-of-care (POC) biosensors. POC diagnostic devices are powerful tools for the detection, diagnosis, and monitoring of diseases at their initial stages. Microfluidic cytometers based on the Coulter principle have recently shown a great potential for POC biosensors for medical diagnosis. One of the most important components in detecting cells by a Coulter counter is a micropore or sensing gate. Therefore, in this study, for counting and sizing the cells using the resistive... 

This study aimed to investigate the penetration of Niosome drug nanocarriers containing curcumin and the effect of PEG surface modification on them in the mucus using a microfluidic chip. The main mucus-forming substance, mucin-type 2, was obtained by extracting from the small intestine of sheep and using calcium ion that regulates the gel properties of the mucus; three different groups, with calcium concentrations of 5, 10, and 15 mM of Calcium were studied as a representative of healthy and Diseased person's mucus. In this research, the study was done on a microfluidic chip; In the processes associated with fabrication of the chip, photolithography, soft lithography, and laser cutting... 

In medical science, preparing a high purity sample of certain kinds of cells plays an important role in studying the characteristics and functionality of cells, detecting in vitro harmful pathogens and helping to find ways of preventing and treating diseases that cause cellular disorders in the human body. The goal of this research is to improve the spiral microchannel with stair-like cross section in order to separate white blood cells from whole blood. First, the efficiency of this method was evaluated numerically, using a developed finite element model. Then, the desired microchannel mold was made using the micromiling method, and we fabricated the chip using soft lithography and pasting... 

Detecting small particles is one of the needs of researchers. Industrial and research developments in nano and biotechnology expands the need of suitable equipments. One of the challenges in this field is detecting the qualitative and quantitative properties in the sample. Until today there are numerous methods to detect the properties of the particles and different commercial machines are presented for this purpose. In this method, based on one the methods of detecting particles, called resistive pulse sensing, a mechanism is composed and by its help 7 um and 800 to 2000 nm particles are distinguished separately. This sensor has two important parts: the fluid and the electronic. In the... 

Over the last few years, exploiting particle sensing systems for micro-nanoparticles has grabbed much attention. Attaining the physical properties of particles using resistive pulse sensing has been one of the utmost applicable methods of sensing particles. Pores are pivotal elements of systems based on resistive pulse sensing. Two electrodes are placed at both sides of the pore, filling the containers with an electrolyte solution. Pulses of particle translocation across the pore can be recorded by applying a voltage across the electrodes. In more developed versions of resistive pulse sensing systems, pore size is tunable to attain polydisperse particles within a dispersion. In subsequent... 

Exosomes are a type of extracellular vesicles which are secreted by cells and could be found in all of human biofluids including blood. The size of exosomes is in the range of 30 – 150 nm. And they have a spherical structure with a phospholipid membrane. Exosomes are very important in academic research for the purpose of diagnostic and therapeutic practices because of their protein and nucleic acid contents.In this study a technological system was developed for isolation of circulating exosomes of human whole blood. This system consisted of a collection of microfluidic chips and protocols in order to extract a purified sample of exosomes from whole blood. First, a chip based on centrifugal... 

Solid-state micro/nanopores have been widely used as a sensor for detection, counting, sizing, and measuring the surface charge of micro (such as cells and bacteria) and nanoparticles (such as viruses, exosomes and DNA) in the last decades and there have been numerous studies regarding the fabrication of single micro/nanopores. Most of the conventional methods require the use of advanced devices such as electron and ion microscopes to fabricate these micro/nanopores. Therefore, the final cost of them is generally high. Given that, in this study, a novel and affordable method is developed for the fabrication of single micro/nanopores of different sizes. This method is based on molding the... 

Liquid marbles are droplets enwrapped by a layer of micro/nanoparticles. Due to the insulation of inner fluid from the environment, the lower evaporation rate of the fluid, and the capability of motion even on hydrophilic surfaces, these liquid marbles, as an alternative to conventional droplets, have attracted the attention of researchers in digital microfluidics. Utilizing ferrofluid as the liquid core of the liquid marbles enables remote control over the liquid marbles by an external magnetic field. In this research, the dynamic behavior of ferrofluid liquid marbles under the magnetic field generated by an electromagnet is investigated. In this research, governing physics on the motion of... 

Thesedays, the electric power industry faces not only increasing electrical demand, but also improving the performance of electrical energy systems. In order to provide these requirements, the concept of smart grid is presented by academic researchers and industry experts. In different parts of a smart grid, the application of various technologies for easy monitoring and control of the system improves its performance. On demand side, making smart is the equivalent of smart consumption management to reduce energy consumption or cost. Considering the high contribution of heating/cooling loads to the energy consumption basket, and the high flexibility of these loads due to thermal inertia, the...