Idrogel

Idrogel, also known as hydrogel, is a three-dimensional network of hydrophilic polymers that can absorb and retain large amounts of water while maintaining structural integrity. The network is usually formed by cross-linking polymer chains, either chemically (covalent bonds) or physically (ionic, hydrogen bonding, or crystalline interactions). The resulting material is soft, rubbery, and highly hydrated, with water contents often exceeding 90% by weight.

Key properties include high biocompatibility, tunable mechanical strength, and the ability to swell or shrink in response to environmental changes such as pH, temperature, ionic strength, or electric fields. This stimuli-responsive behavior makes hydrogels useful in a variety of applications, from medical devices to soft robotics.

Hydrogels can be prepared from synthetic polymers such as polyacrylamide, polyacrylic acid, and poly(N-isopropylacrylamide) or from natural polymers such as alginate, gelatin, and chitosan. They are classified as chemically crosslinked (permanent) or physically crosslinked, and as conventional or smart (stimuli-responsive) hydrogels.

Common applications include contact lenses (including silicone hydrogels for improved oxygen permeability), wound dressings, drug-delivery systems, and tissue engineering scaffolds. In nonmedical fields, hydrogels are used for agricultural water retention, sensors, and soft-robotic components.

The concept emerged in the mid-20th century, with early hydrogel contact lenses developed by Otto Wichterle and Drahoslav Lim in 1961.