Final answer:
A material can be constructed to allow water vapor (moisture) to escape but not allow rainwater to penetrate by using textiles that have specific properties and structures.
Step-by-step explanation:
The key is to create a fabric that is porous enough to allow water vapor to pass through, but has small enough pores or a hydrophobic coating to prevent liquid water from entering.
One example is the use of waterproof breathable fabrics, commonly used in outdoor clothing. These fabrics have a membrane or coating that is made up of microscopic pores that allow water vapor to escape but are too small for liquid water to pass through.
The pores are also coated with a hydrophobic substance that repels water, further preventing water penetration. This allows the fabric to keep the wearer dry from rain while allowing sweat to evaporate.
Another example is the use of moisture-wicking fabrics. These fabrics are designed to pull moisture away from the skin through capillary action, similar to how a paper towel absorbs liquid.
The fabric is made of hydrophilic fibers that attract and absorb moisture, pulling it away from the body and allowing it to evaporate into the air. This property allows the fabric to keep the wearer dry and comfortable even during physical activity or in hot and humid conditions.