Hydrogel and its usage
Abstract
Over the past decades, science has come up with a wide array of peculiar materials that offered solutions to the existing problems all while creating new ones. An exciting example of these peculiar materials is hydrogels. Hydrogels are crosslinked polymer networks with an excellent absorption capacity. Hydrogels exhibit the properties of elastic solids with deformability and softness.
Hydrogels show great swelling and deswelling behaviours in response to the changes in environmental conditions such as pH, temperature, solvent composition, enzymes, electric fields, and light and interesting thing is that we can manipulate properties of hydrogels through different preparation methods and using different types of polymers in the network structure. So, that we can use hydrogel at many desired place by controlling its property but this area is yet to be explored more by science.
Most importantly, hydrogels are biocompatible materials since they are composed of polymer chains. The responsive nature and biocompatibility of hydrogel to environmental changes of hydrogels are useful in many different application areas such as drug delivery systems, tissue engineering, optics, diagnostics, and imaging.
What are hydrogels?
Hydrogels are three-dimensional (3D) cross-linked polymer networks, which can absorb and retain large amount of water. The formation of hydrogels involves a cross-linking process of polymer chains. Such process is also known as the “gelation” process. Based on different gelation mechanisms, gelation can take place either by physical cross-linking (physical gelation) or by chemical cross-linking (chemical gelation) of polymer chains. In the case of physically cross-linked hydrogels, the formation of hydrogel network results from various strong/weak intermolecular interactions between the polymer chains e.g., hydrogen bonds, electrostatic interactions, hydrophobic interactions, crystallization etc.
Properties of Hydrogel
Generally, the properties of the hydrogel can be characterized from about its five aspects, Which are :
A. Physical
It includes swelling ratio, degradability, thermal stability, porosity, etc
B. Chemical
The chemical properties of hydrogels include the chemical composition and the types of functional groups present in the network.
C. Mechanical
The mechanical properties of hydrogels include Young’s modulus, tensile/compression strength, tensile/compression strain, toughness, etc
D. Rheological
Which includes loss/storage modulus, viscosity of the hydrogel. as hydrogels can retain large amount of water within the cross-linked polymer network, they exhibit unique viscoelastic characteristics when undergoing deformation. Using rheometer we can find its viscoelasticity.
E. Biological
Which includes biocompatibility properties. So that they can be used in drug delivery system or tissue healing properties or tissue-engineering.
One of important properties are “self-healing” which refers to the ability of a material to heal the damage autonomously and regain its original properties. Developing advanced self-healing hydrogels has attracted much research interests since the self-healing property could not only prolong the lifespan but also improve the reliability and durability of the hydrogels in various biomedical and engineering
applications. Its self-healing performance can be studied by evaluating the recovery of mechanical properties using tensile test
Advantages
The main advantage current and potential advantages of hydrogels are that they possess a degree of flexibility very similar to natural tissue, due to their significant water content. They are biocompatible, biodegradable and can be injected. Hydrogels also possess good transport properties and easy to modify. Environmentally sensitive hydrogels have the ability to sense changes of pH, temperature, or the concentration of metabolite and release their load as result of such a change.
Disadvantages
Hydrogel are expensive, these are hard to handle and usually weak in nature. In medical application it is difficult to sterlise and some time it react with and cause coagulation in drug delivery system.
Conclusion
Conventionally people think that hydrogel to be mechanically weak with low toughness and having fracture energy (<10J/m2) Such weak mechanical properties limit their uses in a wide range of applications, such as sensors and actuators, soft robotics, and artificial cartilage. These mentioned application have again their biological significance in treatment. Hydrogel materials generally exhibit a number of properties including permeability to oxygen and nutrients, which make these materials attractive for use in biological applications. Hydrogel is thus a promising candidate for TE. Scientists are researching to grow replacement body parts in hydrogels in the future.
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