In material science, water repellency is referred to as “hydrophobicity”. It widely exists in nature: Many plants and animals use hydrophobic surfaces for survival. A good example is the lotus leaf, which features a hydrophobic coating enabling water droplets to gather dirt and bacteria as they bead up and roll off, thus maintaining the leaf's cleanliness. This phenomenon, known as the "lotus effect," illustrates nature's self-cleaning mechanism.

Hydrophobicity has extensive applications in our daily life. A few examples include:

1. General Waterproofing and Protection: Hydrophobic materials are integral in producing waterproof coatings for a variety of everyday products, including clothing, electronics, and water-repellent paints. For instance, waterproof jackets repel rather than absorb water, keeping the wearer dry in rainy conditions. Similarly, non-stick pans benefit from hydrophobic surfaces to simplify cooking tasks like frying eggs, and car manufacturers use these coatings for windshields and seat fabrics to enhance durability and ease of maintenance.

2. Corrosion and Decay Prevention: Hydrophobic coatings can prevent metal and other materials from water-induced corroding or decaying. This is especially important in environments where moisture is prevalent, such as marine settings or humid climates.

3. Environmental Engineering: Hydrophobic materials are pivotal in separating oil from water, aiding in processes like oil spill clean-ups. They can also help in creating more efficient water transport systems, where minimizing water resistance is crucial.

4. Healthcare Applications: In the medical field, hydrophobic materials are used in many medical devices and applications. For example, they can be used to develop wearable devices that monitor vital analytes in sweat, tears, and blood.

In summary, hydrophobicity is a key factor in ensuring protection, cleanliness, efficiency, and functionality across diverse domains, spanning from natural ecosystems to human-engineered environments.