Browsing by Subject "Droplet microfluidics"
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Item Open Access Fabrication and characterization of liquid metal-based micro-electromechanical DC-contact switch for RF applications(CRC Press, 2012) Çağatay, Engin; Noyan, Mehmet Alican; Damgaci, Y.; Cetiner, B. A.; Bıyıklı, NecmiWe demonstrate that room-temperature liquid metal alloy droplets of Eutectic Gallium Indium (EGaIn) and Gallium Indium Tin alloy (Galinstan) can be actuated using electro-wetting-on-dielectric (EWOD) effect. With the application of 80-100V across the actuation electrode and ground electrode, the metallic liquid droplets were observed to be actuated. We have studied the actuation characteristics using different electrode architectures in open-air configuration as well as in encapsulated microfluidic channel test-beds. The resulting microfluidic DC actuation might potentially be used for RF switching applications.Item Open Access Investigating physical properties of hybrid hyaluronic acid and collagen compositions of GelMA microgels toward tissue engineering and organ-on-chip applications(American Chemical Society, 2023-10-13) Çınar, Aslı Gizem; Munir, IqraMicrogels are promising tools in biomedical sciences to be utilized as 3D cell culture scaffolds and cell-delivery or drug-delivery vehicles. Carrying the desired properties of hydrogels, they can be fabricated from various materials in different shapes and sizes. Additionally, due to their increased surface-to-volume ratio, they provide fast nutrient, waste, and species transport with altered solute–material interactions. Despite their micrometer size and the differentiated behaviors that come with these properties, the characterization methods utilized so far to investigate their physical and morphological properties are majorly carried out on their bulk versions, resulting in inaccurate estimates and somewhat missed information. Here, in this work, swelling, degradation, and morphological examination assays curated for microgels are proposed to reflect the actual behavior of microgels. Accordingly, gelatin methacryloyl, complemented with hyaluronic acid methacrylate and collagen to set an example of different types of polymer networks, was fabricated into microgels using a droplet microfluidic platform with in situ photopolymerization. An easy washing and drying process is proposed as a substitution for the harsh conditions of lyophilization for morphological analysis, resulting in a much more accurate picture of the porous structures. Swelling and enzymatic degradation assays, usually done by immersing a bulk hydrogel in a medium for an extended period, are substituted with swelling and degrading individual microgels in a custom-made platform that enables real-time, statistically significant data acquisition. Results showed that, due to their small size, swelling occurs in a matter of minutes, with different temporal profiles depending on the medium and microgel compositions, and enzymatic degradation takes place in a couple of hours with varying behaviors, changing due to the polymers, enzyme type, and concentration. Overall, this work highlights the necessity and importance of characterizing microgels in their respective sizes, hopefully advancing their utilization in microphysiological systems and biomedical applications.Item Open Access Real-time impedimetric microfluidic droplet measurement: IDM(2019-08) Saateh, AbtinDroplet-based micro uidic systems require a precise control on 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, coplanar electrodes were used, and con gured in di erential measurement mode for impedimetric measurement of size and velocity. To obtain the size of the droplets, detailed 3D nite element simulations of the system were performed. The interaction of the non-uniform electric eld and the droplet was investigated. The electrode geometry optimization steps were described and design guideline rules were laid out. Size of the electrodes was optimized based on the simulations for droplet lengths ranging from 300 to 1500 μm. A user-friendly software was developed for real-time observation of droplet length and velocity together with in-situ statistical analysis results. A detailed comparison between impedimetric and optical measurement tools is given. Finally, to illustrate the bene t of having real-time analysis, iDM was used for experimental studies. First study case is the response time of the 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 stead-state size required by the assay of interest. Second, an evaluation chip was designed to investigate e ective factors and their interplay with droplet length variation. A comprehensive design of experiment (DoE) method is utilized. Analyzing the obtained results revealed e ect of each factor and their interactions. Exploiting results of this study contributes to monodisperse micro uidic droplet generation. Monodisperse polymeric particles of polyethylene glycol were synthesized to demonstrate the potentials of monodisperse droplet generation in biochemical synthesis/analysis.