Hydrogels are three-dimensional polymers that can absorb large amounts of water and have a wide range of applications in various fields. They can be natural, synthetic, or semi-synthetic. They are classified based on their structure (amorphous, crystalline, semicrystalline) and the type of crosslinking (physical or chemical). In biomedical applications, polysaccharides such as alginate, chitosan, and hyaluronic acid are commonly used, often combined with other polymers to improve mechanical properties. Hydrogels can also be synthesized in microreactors, as they allow precise control of chemical reactions in microchannels, often in combination with biocatalysts and hydrogel materials such as alginate and PVA. Microfluidics enables the creation of droplets that act as microreactors with various channel geometries, such as "cross-flow," "co-flow," and "flow-focusing." Gelation in microfluidic systems allows the formation of hydrogel droplets, with gelation occurring either before or after droplet formation, enabling the creation of microparticles with different shapes and sizes. In the lab, we focused on the preparation and analysis of hydrogels and studying their behavior in different pH conditions. We prepared a 1% chitosan solution in 1% acetic acid and a 2% alginate solution, which we mixed on a magnetic stirrer, along with buffer solutions with pH values of 3, 5, and 7. We also prepared calcium chloride solutions and examined how these affected the behavior of the hydrogels. We combined the hydrogels with buffers and observed whether they precipitated or gelled at different pH values. Using a microfluidic system, we formed alginate droplets in calcium chloride at different concentrations, examining the effect of tube dimensions on droplet size and calcium chloride concentration. Later, we used a microdroplet generator, where we added dodecane and alginate, and studied the influence of flow rates of both substances on the size and stability of the droplets.
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