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. A. 1 only
2. B. 1 and 2 only
3. C. 2 and 3 only
4. D. 1, 2 and 3

Answer: D

Explanation

Hydrogels are cross-linked polymeric networks capable of absorbing large amounts of water, making them highly versatile. Statement 1 is correct; their biocompatibility and ability to swell or shrink make them ideal for controlled drug delivery systems, releasing medication over time. Statement 2 is also correct; hydrogels can be used in cooling applications, including potentially in mobile air-conditioning systems, due to their water-absorbing and evaporative properties. Furthermore, statement 3 is correct; research has shown that hydrogels possess excellent anti-friction and anti-wear properties, making them suitable for use as industrial lubricants, particularly in situations requiring low friction and biocompatibility. Thus, hydrogels have applications in all three mentioned areas. This question highlights the interdisciplinary nature of modern materials science and its diverse applications, a common theme in UPSC Science & Technology.