Browsing by Author "Saqib, Muhammad"

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Open Access
Alternating droplet formation by using tapered channel geometry
(Nature Publishing Group, 2018) Saqib, Muhammad; Şahinoğlu, O. Berkay; Erdem, Yegân
The ability to produce a controlled sequence of alternating droplets from two separate sources inside a microfluidic system brings several advantages in microfluidic analysis. The effectiveness of this technique for use in an application depends on the ability of the device to replicate the pattern continuously and accurately. In this work we studied the effect of the dispersed phase channel geometry on generating a repeating pattern of alternating droplets in a cross junction microfluidic device. By measuring the radius of curvature of a droplet at the time of break up, and calculating the Laplace pressure using these values, we analyzed how the angle of taper of the dispersed phase inlet channel has an influence on the pattern repetition and uniformity of formed droplet size and spacing in between. The performance of devices with different angle of taper values were studied experimentally. This comparative study indicated that the ability of a cross junction device to generate alternating droplets with uniform size and spacing is highly dependent on the angle of taper of the inlet channels; and it improves with larger taper angles.
Open Access
Effect of channel geometry on alternating droplet generation
(2018-05) Saqib, Muhammad
Droplet based micro uidics has been one of the popular topics in micro udics research for the past two decades due to several advantages which include: less amount of reagent (sample) being used, enhanced mixing in the drops due to chaotic advection, low thermal mass and large surface to volume ratio which results in e cient heat transfer and encapsulation of reagents in droplets. Producing droplets from two sources inside the same micro-channel has been attempted by several research groups with great success and it carries great signi cance due to its applications in chemical synthesis, biological analysis and targeted drug delivery. While there are geometries available to produce synchronized alternating droplets, the mechanism of alternation in such device has not been studied. In this work a cross junction device (also known as a double T-junction device)is used; and the e ect of the taper angle of the side inlet channels on the continuous generation of an alternating pattern is studied. It was found that a higher value of the taper angle results in more e cient and constantly repeating alternating pattern of droplets from the two sources. This study includes the statistical analysis of the experimental data to compare the performance of devices with di erent taper angles for side channels. Moreover the experimental data is used to measure the radii of curvature at the instant of break o and used to calculate the Laplace pressure drop across the junction which enables us to compare the total pressure drop across the junction for devices with di erent taper angle values. Using the total pressure drop it was concluded that the hydraulic resistance of the side inlet channels is the key factor in synchronized alternating droplet pattern generation. In order to con rm the calculated values, a computational study is also performed which further substantiates the theory. Furthermore, using the tapered channel devices, di erent patterns are generated that are referred to as barcodes, by employing di erent ow rate combinations at the dispersed phase inlets. Finally it was showed how to generate barcodes composed of droplets with di erent and same viscosity. The signi cance of being able to generate di erent patterns is related to being able to separately identify droplets from each sources while using automation in the system since the droplet size and spacing remains uniform.
Open Access
Microfluidic methods in janus particle synthesis
(Dove Medical Press Ltd, 2022-09-19) Saqib, Muhammad; Tran, Phong A.; Ercan, Batur; Yegan Erdem, Emine
Janus particles have been at the center of attention over the years due to their asymmetric nature that makes them superior in many ways to conventional monophase particles. Several techniques have been reported for the synthesis of Janus particles; however, microfluidic-based techniques are by far the most popular due to their versatility, rapid prototyping, low reagent consumption and superior control over reaction conditions. In this review, we will go through microfluidic-based Janus particle synthesis techniques and highlight how recent advances have led to complex functionalities being imparted to the Janus particles. © 2022 Saqib et al.
Open Access
Synthesis of anisotropic magnetic polymeric janus particles by in situ separation of magnetic nanoparticles in a microfluidic device
(American Chemical Society, 2023-11-20) Saqib, Muhammad; Ercan, Batur; Erdem, E. Yegan
Magnetic Janus particles have been studied extensively for medical and biological applications owing to their controllable mobility in fluid media. In this work, we report a novel microfluidic device designed for the synthesis of magnetically anisotropic Janus particles made of poly(ethylene glycol) diacrylate and embedded with magnetic iron oxide nanoparticles. Our method consists of a droplet generation step followed by magnetic separation using an external magnetic field and ultraviolet polymerization. The synthesized particles exhibit a monodisperse size distribution with a standard deviation of less than 3.5%, which is among the best size distributions obtained in the literature for magnetic Janus particles. The anisotropic magnetic property of the particles enable them to rotate about their own axes in the presence of an external magnetic field, introducing another degree of freedom to their motion. This microfluidic technique is simple, one-step, and versatile, offering control over the size distribution to synthesize magnetically anisotropic Janus particles.
Open Access
Synthesis of magnetically anisotropic janus particles by droplet-based microfluidics
(2024-01) Saqib, Muhammad
In the past decade Janus particles have been extensively utilized by the scientific community for potential uses such as cell encapsulation and assembly, DNA assays, biological multiplexing , targeted drug delivery, noninvasive imaging, theranostics, microlenses, reflection-mode displays, removal of organic and metal pollutants and water decontamination. Due to their multi functional characteristics, stemming from their anisotropy, they are superior to conventional monophase particles. Even though there are several established synthesis methods for Janus particles, microfluidics-based methods are by far the most convenient and reliable due to low reagent consumption, monodispersity of the resultant particles and efficient control over reaction conditions. Droplet-based microfluidics is the most popular technique for the reliable synthesis of Janus particles and even though it has been extensively explored there are many aspects of the conventional droplet-based microfluidics techniques that either result in poor anisotropy of the synthesized particles or involve off-chip processing. In this work a simple and novel droplet-based microfluidic technique is utilized to synthesize magnetically anisotropic Janus particles. Using this method magnetically anisotropic Janus particles are synthesized by using droplets as templates. The droplets contain magnetic nanoparticles and are exposed to ultraviolet radiation while passing through a magnetic field. The magnetic field renders the droplet anisotropic by attracting the magnetic nanoparticles to one hemisphere while at the same time the ultrviolet exposure initiates polymerization of the prepolymer phase. The microfluidic device was optimized by using numerical simulations and experimental observations. The magnetic flux density was optimized by using a magnetic flux density map. The synthesized particles were imaged under an optical microscope to observe their size distribution and scanning electron microscope to confirm complete polymerization and the magnetic anisotropy was confirmed by observing the motion of the particle in the presence of an external magnetic field. The synthesized particles were observed to be monodisperse and exhibited rotation about their own axis which is characteristic of magnetically anisotropic particles. Further another design was developed to merge droplets from two dispersed phase streams in a Janus orientation by optimizing the angle of merging. With this device the merged droplet was observed to contain the constituents of its two hemispheres distinct from each other. Using this device TiO2-Fe2O3 and SiO2- Fe2O3 magnetically anisotropic Janus particles were synthesized. The synthesized Janus particles were observed under the optical microscope and the scanning electron microscope. Moreover the magnetic response of the Janus particles was also observed using a permanent magnet. These types of Janus particles could be potentially used as micromotors for microcargo transport because of their magnetic properties or for DNA assay applications.