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Microfibre cloths have become really popular during the last years. I just got one as an advertisement gift from the phone company. They’re handy to clean glasses, all kinds of screens, windows, mirrors and plastic surfaces, quickly and without the use of water. If dirty, put the cloth in the laundry, add detergent, and they’re as good as new.

But what are microfibers and what can they do that a Kleenex can’t?

[Image]Cotton cloths or paper wipes are mostly made of cellulose. Cellulose is a polymer, a long molecule that repeats a shorter structure up to some thousand times. Cellulose is hydrophile, meaning it likes to bind to water molecules. What it doesn’t like though is binding to fat molecules, which are themselves hydrophobic and don’t like to bind to water.

Cotton and paper tissues thus work badly for removing fatty stains, such as finger prints from glasses. If you want to get rid of these you have to use water and detergents on the cloth. Detergents are made of molecules that allow mixing water with fatty substances. With the detergent, the wet cotton cloth does a good job with the grease. Except that then it takes a long time to dry because now all the water molecules are attached to the cellulose polymers.

[Image] Cross-section of single microfibre,
electron microscope. Image Source. Microfibers are also polymers, but that’s where the similarities end. Microfibers are synthetic polymers and usually much longer than the cellulose fibers won from organic materials. They are also about an order of magnitude thinner, typically only a few micrometers.

The microfibres used for cleaning cloths are normally a mixture of polyester and polyamide. Polyesters like to bind to fat, which is why the cloths can be used to wipe away grease without adding detergents. Polyesters however don’t like to bind water. Some polyamides do, but the water absorption of the microfibre cloths comes mostly from a clever production technique that increases the surface area of the fibres and allows for capillary action to suck up the water.

This technique works as follows. The long microfibers are not produced separately, but in a mixture of polyesters and polyamides that are arranged as alternating wedges, much like pieces on a cake. These mixed fibres are later split up by high pressure water jets (the image above shows the result). This procedure allows to produce much finer fibres than would be possible to produce directly, and since the microfibers are thin to begin with, it creates very porose materials that have a large surface in a small volume.

[Image] Cross-section of microfibre cloth, electron
microscope image. Source: hotrodworks.net These splitted fibres are then woven or pressed into textiles (see image right). The resulting cloth is lightweight and binds to fat so you can wipe those fingerprints away easily. The material sucks up water, but since most of the water is stored in the pores between the fibres rather than binding directly to them (as is the case with cotton), microfibre cloths dry much faster than cotton.

Microfibres are not a new invention. The production technique goes back to research in the 1950s, but it wasn’t until the early 90s that they were marketed to households, a trend apparently started by the Swedes. During the last decade or so, microfibers have become quite common, especially for cleaning purposes, and, because they dry quickly, for sport and outdoor clothes.

So the next time you wipe the earwax off your display, I hope you appreciate the science behind this not-so-simple cloth.