I'm currently making calcium alginate films by solvent casting followed by imersion in CaCl2 solutions. After the imersion, while drying the films, they start shrinking and getting the form of a hyperbolic paraboloid. I already tried to change the concentration of CaCl2, the plasticizer and the plasticizer concentration. The drying occurs at ambient temperature and pressure. I cannot lyophilize nor pressurize the drying process. Is there a way to hold it in a circular shape without risking tearing them apart in the process?
I have not been deaaling specifically with the subject, but I think the cause is may be CaCl2 itself. Did you notice a reduction of the shrinking when deceasing its concentration?
You may try to use polyeylene glycol (PEG) if compatible with rest of your system PEG 600 1-3% calculated on the total system.
Good luck.
G. Bognolo
Shrinkage of Alginate Hydrogel Bioinks Potentially Used in 3D Bioprinting Technology
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Abstract:
Hydrogels are cross-linked polymeric structures, which consist of up to approximately 90% water, the remainder is polymer chain. Retention of large volumes of water in the intermolecular space is related to the presence of hydrophilic functional groups in the network. The unique hydrogels properties, such as porosity, and biological and mechanical properties, make them suitable for a wide range of applications, especially in the medical sector. Furthermore, ease of modification and good printability are expected in 3D bioprinting technologies. Nevertheless, to maintain their structure and softness, hydrogels must be stored in suitable conditions to prevent water vaporization. The water removal from the hydrogel network results in weight reduction, structural and volumetric changes. It is a considerable challenge for the printouts manufactured by 3D bioprinting technology, where hydrogel products are exposed to drying during the production process, which may affect their shape change and shrinkage. The paper presents a crosslinking process of a hydrogel-based on sodium alginate and the shrinkage of dried hydrogels depending on the crosslinking procedure. An investigation focused on the alginate hydrogel water content, as well as shrinkage of alginate hydrogel degree depending on the concentration of the cross-linking (CaCl2) solution and the duration of the process. For longer cross-linking time or using higher cross-linking agent concentration, the cross-linking was more efficient. However, it is necessary to optimize the parameters for the bioprinting process.
Add different amount of citirc acid as crosslinking and you can add the final film in a desiccantor at 45%RH
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