Browsing by Subject "Microreactors"
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Item Open Access Chitosan coated iron-oxide nanoparticle synthesis using a droplet based microfluidic reactor(IEEE, 2019-06) Wahab, Malik Abdul; Erdem, E. YeganA microfluidic reactor for the synthesis of chitosan coated iron-oxide nanoparticles is described. Tapered double T-junction is used to generate droplets of reactants (iron chloride solution and chitosan solution) which were merged using a pillar array. Third reactant ammonia solution is introduced after the mixing of already merged droplets. Ammonia solution initiates the reaction and precipitates are collected at the outlet. Transmission electron microscope (TEM) imaging along with Fourier transform infrared spectroscopy (FTIR) is used to characterize the nanoparticles. These nanoparticles have applications in nano-medicine where they can be used as drug carriers.Item Open Access Design of a droplet-based microfluidic system for hybrid polymer nanoparticle synthesis(Bilkent University, 2021-12) Şahinoğlu, Osman BerkayDroplet microfluidics is advantageous in synthesizing microparticles for both confining their size to the physical dimensions of the droplet and providing a monodisperse result due to rapid mixing inside the droplets. Thusly named microreactors became the focus of the microfluidics community in the recent decade due to their superior ability to control the reaction environment. In this study, for the application of microreactors, a hybrid organic-inorganic material that became prominent in last years named polyhedral oligomeric silsesquioxane (POSS) is chosen. POSS is a polymer that, beside its hybrid nature, shows heat resistance property which made its use in protective painting applications and high radical group affinity that can be utilized to further configure its material properties. This study proposes two microreaction systems for monomer POSS with ther-mal and photopolymerization methods that aim to increase monodispersity and solve the clogging problem encountered in previous studies by introducing the oil phase in the system. Feasibility of systems was investigated numerically using COMSOL Multiphysics and analyses showed adequate heating of and mixing in microreactors. A robust post-processing procedure is proposed to remove excess oil from the sample. Measurements showed microdroplet and sub-micron particle generation where the size distribution of these particles are quantified using MATLAB. Though the use of oil in the system proved to be another challange, hexane based substitute materials are proposed for future work.Item Open Access Droplet-based microfluidic systems for silica coating and synthesis of conjugated polymer nanoparticles(Bilkent University, 2015-07) Özkan, AlicanNanoparticles have unique electronic, optic and magnetic properties due to their large area to volume ratio. In order for them to preserve their properties for longer times, some of them need to be coated with a protective layer such as silica (silicon dioxide) layer. This coating has to be made uniformly to obtain monodisperse size distributions, which is essential to obtain uniform properties for all nanoparticles. Obtaining monodisperse size distribution relies on the control over reaction conditions such as residence time, concentration and temperature. This thesis presents a microuidic reactor that can achieve strict control over reaction conditions by utilizing a meandering geometry of microchannels and droplet-based ow. Meandering channels reduce the time needed for mixing due to the reduced diffusion lengths; whereas droplet-based flow provides uniform residence time inside the reactor due to the circulating flow profile of droplets as opposed to parabolic ow profile in straight channels. Before fabricating the device, the mixing performance of droplets at different channel cross-sections and meandering geometries were simulated by using Comsol Multiphysicsr. As a result, it is concluded that the channel cross-section and meandering dimensions should be as small as possible for faster mixing. Based on these simulation results, the microuidic device was designed and later fabricated in polydimethyl siloxane (PDMS) by using the soft lithography technique. This system was used to understand the effect of solvent concentrations and residence time on silica formation in order to be able to control the coating thickness compared to batchwise methods. Initially silica nanoparticle formation inside droplets were tested; and 102 nm ± 4 nm diameter of silica nanoparticles were obtained; which is a significant improvement compared to the bath-wise synthesis methods. Additionally, experimental studies on the synthesis of green Conjugated Polymer Nanoparticles (CPN) was also conducted. By using three different methods, bulk solution, continuous ow and droplet-based ow, nanoparticles were synthesized. From the results, it was acquired that droplet-based ow provided higher quality of nanoparticles in terms of nanoparticle size, uniformity and monodispersity.Item Open Access Multi-temperature zone droplet-based microreactor for increased temperature control in nanoparticle synthesis(Wiley-VCH Verlag, 2014) Erdem, E. Y.; Cheng, J. C.; Doyle, F. M.; Pisano, A. P.Microreactors are an emerging technology for the controlled synthesis of nanoparticles. The Multi-Temperature zone Microreactor (MTM) described in this work utilizes thermally isolated heated and cooled regions for the purpose of separating nucleation and growth processes as well as to provide a platform for a systematic study on the effect of reaction conditions on nanoparticle synthesis.