The corona virus SARS-CoV-2 is tiny!
Its diameter is only 125 nm, so it cannot even be seen with a light microscope.
The virus is usually transmitted via droplets in the air. Most droplets are also very small. About 5000nm ( 5µm).
Homemade face masks should ideally be able to catch these droplets. To do this, the pores must at least be small enough that the droplets stick to the fabric.
The pores of this thin cotton fabric are very large (> 100 µm). The fabric can hardly retain droplets.
Due to the tight weave structure of this tea towel, the pores are quite small. (< 20 µm). In double layer, droplets are safely captured well.
This meltblown fleece from a surgical mask is not tightly woven, but because of the many layers it can catch droplets very effectively.
The size of the particles - be it in food, pharmaceuticals or building materials - is responsible for many qualities of a product.
- Large particles taste crumbly, small ones creamy. But we cannot taste too tiny.
- Small particles are usually easier to mix and blend, but can also cause harmful fine dust.
Particle size measurement is a good way of characterising them. A classical measuring method is statistical laser diffraction. For this, the particles to be analysed are held in a laser beam and the resulting diffraction pattern is analysed.
The disadvantage is obvious: statistical data are collected. Outliers get lost in the masses. In addition, usually only the size is recorded, but not the shape and structure of the individual particles. But these are also extremely important functional and quality characteristics.
Scanning electron microscopy is a useful method of simultaneously recording all these properties - size, shape, structure, distributions - at the same time. It records the size, structure and, if necessary, also the contents of each individual component.
