A hydrogel is a network of polymer chains that are hydrophilic, or water loving. Hydrogels are three-dimensional (3D) networks that can swell up to 1000 times their dry weight in water. They are used in a variety of biomedical applications such as contact lenses, drug delivery, wound dressings, and tissue engineering scaffolds.
Most hydrogels are made from polymers such as polyacrylamide, polyethylene glycol, and polyvinyl alcohol. These polymers are cross-linked together to form a 3D network. The degree of cross-linking determines the properties of the hydrogel. For example, more cross-linked hydrogels are stiffer and less permeable to water and molecules, while less cross-linked hydrogels are more porous and soft.
Hydrogels can be further characterized by their elasticity, degree of hydration, and transport properties. Elasticity is a measure of a material’s ability to deform and return to its original shape. The degree of hydration is a measure of how much water a hydrogel can absorb. Transport properties refer to a hydrogel’s ability to allow molecules to diffuse through it.
Most hydrogels are highly hydrated, meaning they can swell up to 1000 times their dry weight in water. This high degree of hydration gives them a soft, jelly-like consistency. Hydrogels are also highly elastic, meaning they can be deformed and will return to their original shape. Lastly, hydrogels are permeable to water and small molecules, making them ideal for drug delivery and tissue engineering applications.
There are many different types of hydrogels, each with their own unique properties. Choosing the right hydrogel for a particular application can be a challenge. However, characterization techniques such as those described above can help scientists and engineers select the best hydrogel for their needs.
Hydrogels are versatile and complex materials that have a wide range of potential biomedical applications. Despite their potential, there is a lack of characterization methods for hydrogels that would allow for tailoring of their properties for specific applications. In order to provide guidance for the development of such methods, we have compiled a review of the existing methods for characterizing hydrogels with a focus on their biomedical applications. This review provides an overview of the physicochemical properties that are typically characterized, methods for characterizing these properties, and how these methods can be applied to optimize hydrogels for specific biomedical applications.