A droplet will not penetrate through the hydrophobic membrane to contaminate the wearers mouth or nose. Hydrophilic materials such as coffee filters, wipes, paper towels are not ideal because the droplets will spread out, penetrate through, and contaminate the wearer's mouth and nose. You can test whether a material is hydrophobic or hydrophilic. If water beads up on a material, it is hydrophobic. If it spreads out and penetrates, it if hydrophilic.
2. Two layers of woven fabrics, which have better filtration efficiency.
3. Nose wire. This allows the wearer to shape the mask tightly around the nose to limit exposure. It also helps to prevent glasses from steaming up as you breath.
4. Elastic around the head, not just over the ears.
This is a fully washable filter system that retains its hydrophobic properties after being washed.