UPSC Prelims 2024 Q36: Hydrogels and Their Uses — Explained
In which of the following are hydrogels used?
1. Controlled drug delivery in patients
2. Mobile air-conditioning systems
3. Preparation of industrial lubricants
Select the correct answer using the code given below:
- 1 only
- 1 and 2 only
- 2 and 3 only
- 1, 2 and 3
Answer: (a) 1 only
Statement-wise explanation
- 1: correct — A hydrogel is a three-dimensional network of water-loving polymer chains that can hold a large amount of water without dissolving. Drugs can be loaded into this network and then released slowly as the gel swells or breaks down. That keeps drug levels steady and means fewer doses. Indian labs have built such systems: JNCASR made an injectable silk-fibroin hydrogel for sustained insulin delivery, and IIT Madras made one that releases medicine in response to inflammation.
- 2: incorrect — Mobile (vehicle) air-conditioning works on a vapour-compression cycle. A refrigerant gas such as R-134a or R-1234yf passes through a compressor, a condenser, an expansion valve and an evaporator. No hydrogel has a part in that cycle. Labs are testing hygroscopic hydrogels for passive cooling films and moisture-absorbing dehumidifiers. These are still research prototypes, not parts used in vehicle AC systems, and the official key treats this statement as wrong.
- 3: incorrect — Industrial lubricants are mostly mineral oils refined from crude petroleum, or synthetic oils such as polyalphaolefins and esters. Greases are made by thickening these oils with soaps. Water-based hydrogels evaporate, freeze and break down under heavy loads and high temperatures, so they do not suit machinery. Research on hydrogel lubrication aims at cartilage replacement and medical devices, not industrial lubricants.
How to eliminate
Basic science knowledge is enough to fix Statement 1 as correct. Drug delivery, wound dressings and contact lenses are the best-known uses of hydrogels and appear often in science news, so every option you consider must include 1. That leaves 1 only, 1 and 2, or all three. The question then turns on two industrial claims. Ask what a hydrogel is mostly made of: water. A material that is mostly water cannot survive the heat and load in machinery, so Statement 3 is unlikely. Vehicle AC runs on a refrigerant gas cycle and does not need a gel. The trap: research papers on hydrogel cooling films and hydrogel lubrication exist, and over-reading them pushes candidates toward 'all three'. UPSC asked about uses, not lab experiments. Fact to remember: hydrogels in real use are mainly biomedical and personal-care products (drug delivery, wound care, contact lenses, tissue engineering, diapers), plus water retention in farm soil.
Know more
What is a hydrogel? A hydrogel is a network of hydrophilic (water-loving) polymer chains, cross-linked so that it swells in water but does not dissolve. Many hydrogels are about 90% water by weight. Because they are soft, wet and porous, they behave much like living tissue.
Types by cross-linking
- Physical gels: chains held together by weak bonds (hydrogen bonds, ionic links). These are often reversible, such as gelatin or alginate.
- Chemical gels: chains joined by covalent bonds. These are more stable.
Smart or stimuli-responsive hydrogels swell or shrink in response to temperature, pH, glucose or inflammation. This is what makes them useful for releasing a drug on demand.
| Field | Established use |
|---|---|
| Medicine | Controlled or sustained drug release (insulin, anti-cancer drugs), injectable gels |
| Wound care | Moist dressings that absorb fluid from the wound |
| Eye care | Soft contact lenses (pHEMA, silicone hydrogels) |
| Tissue engineering | Scaffolds for growing cells and regenerating cartilage |
| Hygiene | Superabsorbent sodium polyacrylate in diapers and sanitary pads |
| Agriculture | Soil water-retention granules for dry areas |
Research frontier, not yet everyday use: hygroscopic hydrogel films for passive cooling, hydrogel desiccants for dehumidifying air and harvesting water from air, and hydrogel coatings that mimic cartilage lubrication.
Where hydrogels sit in materials science: hydrogels are soft matter, the same family as foams, pastes and liquid crystals. These materials hold their shape at rest but deform easily under force.
NCERT Concepts to Revise
- Petroleum: Statement 3 concerns industrial lubricants; knowing what crude oil is made of helps you judge what such lubricants are normally made from.