Browsing by Author "Asghari, Mohammad"

Now showing 1 - 5 of 5

Open Access
Impedance-based viscoelastic flow cytometry
(WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim, 2019) Serhatlıoğlu, Murat; Asghari, Mohammad; Guler, M. T.; Elbuken, Çağlar
Elastic nature of the viscoelastic fluids induces lateral migration of particles into a single streamline and can be used by microfluidic based flow cytometry devices. In this study, we investigated focusing efficiency of polyethylene oxide based viscoelastic solutions at varying ionic concentration to demonstrate their use in impedimetric particle characterization systems. Rheological properties of the viscoelastic fluid and particle focusing performance are not affected by ionic concentration. We investigated the viscoelastic focusing dynamics using polystyrene (PS) beads and human red blood cells (RBCs) suspended in the viscoelastic fluid. Elasto‐inertial focusing of PS beads was achieved with the combination of inertial and viscoelastic effects. RBCs were aligned along the channel centerline in parachute shape which yielded consistent impedimetric signals. We compared our impedance‐based microfluidic flow cytometry results for RBCs and PS beads by analyzing particle transit time and peak amplitude at varying viscoelastic focusing conditions obtained at different flow rates. We showed that single orientation, single train focusing of nonspherical RBCs can be achieved with polyethylene oxide based viscoelastic solution that has been shown to be a good candidate as a carrier fluid for impedance cytometry.
Open Access
Lab-on-a-chip platforms for disease detection and diagnosis
(Wiley Blackwell, 2018) Işıksaçan, Ziya.; Güler, M. T.; Kalantarifard, Ali; Asghari, Mohammad; Elbüken, Çağlar; Altıntaş, Z.
The adaptation of silicon electronics microfabrication technologies to other materials led to the birth of microfluidic systems. These systems allow investigation and control of fluids at micrometer scale. Due to the wide variety of applications of microfluidics, several research groups have been involved in the development of basic microfluidic components. After the development of fundamental fluid handling components, these technologies have been integrated for numerous applications one of which is disease detection and diagnostics. This chapter summarizes the microfluidic platforms that are mature enough for adaptation towards disease detection. The microfluidic platforms were discussed under six categories: continuous flow, paper‐based, microdroplets, digital microfluidics, compact disk‐based, and wearable platforms. Seminal works and recent developments in each category have been presented together with successful commercial examples. It is worth noting that some studies straddle more than one category, therefore, this classification is strictly for the ease of the reader. Each section discusses the benefits of a specific microfluidic platform. Engineering of microfluidic systems lead to lab‐on‐a‐chip (LOC) systems that can be used for diagnostics whether at point‐of‐care as portable systems or at clinical settings as advanced detection systems. The increasing awareness on personalized treatments proves the importance of such democratizing technologies. The increasing market share of microfluidic platforms in nearly all sectors is also an indication of the bright future of microfluidics and lab‐on‐a‐chip systems. The chapter is ended with a future outlook.
Open Access
Manipulation of particles using inertial microfluidics and viscoelastic fluids
(2018-03) Asghari, Mohammad
Recent years have witnessed an elevated trend in using miniaturized and labon- a-chip systems in biomedical devices due to numerous advantages including minimal sample/reagent consumption, portability, and superior performance. One of the key challenges within these microsystems is to precisely manipulate and order bio-particles. Various techniques have been introduced to accomplish this mission. Inertial microfluidics enables lateral migration of particles and cells in laminar flow regime due to the velocity gradient effect in moderate Reynolds number. Moreover, viscoelastic fluids exploit intrinsic elastic property of the fluids to transfer particles and cells across laminar ow streamlines. Both methods utilize inherent properties of fluids alleviating any external force field inducer. This dissertation elucidates inertial and viscoelastic effects on particles and cells motion and investigates some unexplored migration behaviors. For inertial migration study, a new fabrication method termed tape'n roll is introduced enabling to study migration in both 2D and 3D structures. To better unravel the covert mechanism of migration, computational model is applied. For viscoelastic behavior study, focusing of particles inside three different viscoelastic fluids in a straight glass capillary tube is scrutinized through optical system and image processing.
Open Access
Real-time impedimetric droplet measurement (iDM)
(Royal Society of Chemistry, 2019) Saateh, Abtin; Kalantarifard, Ali; Çelik, Oğuz Tolga; Asghari, Mohammad; Serhatlıoğlu, Murat; Elbüken, Çağlar
Droplet-based microfluidic systems require a precise control of droplet physical properties; hence, measuring the morphological properties of droplets is critical to obtain high sensitivity analysis. The ability to perform such measurements in real-time is another demand which has not been addressed yet. In this study, we used coplanar electrodes configured in the differential measurement mode for impedimetric measurement of size and velocity. To obtain the size of the droplets, detailed 3D finite element simulations of the system were performed. The interaction of the non-uniform electric field and the droplet was investigated. Electrode geometry optimization steps were described and design guideline rules were laid out. User-friendly software was developed for real-time observation of droplet length and velocity together with in situ statistical analysis results. A comparison between impedimetric and optical measurement tools is given. Finally, to illustrate the benefit of having real-time analysis, iDM was used to synthesize particles with a predefined monodispersity limit and to study the response times of syringe pump and pressure pump driven droplet generation devices. This analysis allows one to evaluate the ‘warm-up’ time for a droplet generator system, after which droplets reach the desired steady-state size required by the application of interest.
Open Access
Tape'n roll inertial microfluidics
(Elsevier, 2019) Asghari, Mohammad; Serhatlıoğlu, Murat; Güler, M. T.; Elbüken, Çağlar
Particle focusing and separation in microfluidic devices are critical for biological and medical applications. Inertial microfluidics is used for high throughput bio-particle focusing and separation. Most of the inertial microfluidic systems use planar structures for squeezing the particles in streams. Particle manipulation in 3D structures is often overlooked due to the complexity of the fabrication. In this study, we introduce some novel microchannel designs for inertial microfluidics by using a simple fabrication method that allows construction of both 2D and 3D structures. First, inertial migration of particles in 2D layouts including straight, spiral, and square spiral channels is investigated. Afterward, by applying a “tape’n roll” method, helical and double oriented spiral channels are configured and unexplored inertial migration behaviours are observed. Thanks to the simplicity of the fabrication and the unique characteristics of the new designs, high performance microfluidic inertial migration results can be obtained without any need for complicated microfabrication steps. The design optimization cycle can also be shortened using a computational approach we introduce in this study.