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Modeling the production of belly button lint

Why does a tuft of tint (called navel fluff or belly button lint) appear in my navel at the end of the day? This question must have occurred to most men and some women. Yet, only a couple of researchers have attempted to address this question formally. A new mathematical model developed by me aims at shedding light on the physical mechanism underlying the production of navel fluff.

The model is build up on the general notion existing in the literature that the body hair (on chest and abdomen) is essential for the creation of navel fluff. An earlier study confirmed that the navel fluff is composed of fibers originating from one's shirt or underclothes. The new model reveals the role played by the microstructural features on the hair in channeling the cotton fibers to the navel. The scaly structure of hair is reminiscent of overlapping roof tiles, causing the frictional characteristics of the hair surface to be different in different directions. This asymmetric properties, combined with the fact that hairs around the navel stoop towards the navel, facilitate a one-way street for transporting the shirt fibers to the navel. The new model is capable of predicting the rate at which the fibers are accumulated in a navel and confirms the experimentally reported value of navel fluff mass.

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