Have you ever found a tuft of plong in the navel at the end of the day? You are not the only ones! According to an online survey conducted by the popularizer Dr. Karl Kruszelnicki, about 83% of men and 43% of women regularly produce umbilical hornbeam. A phenomenon as common as it is curious, the “Belly Button Lint“(BBL), which we know as fluff or “hornbeam” of the navel, has been the subject of one surprisingly rigorous scientific study. It is a small mass of fiber that is formed inside the navel due to the progressive accumulation of tiny elements from our clothes, dust particles present in the environment, skin cells, sebum produced by the skin and sweat.
The article published on Scientific Reports from P. Deepu of the Iit of Patna proposes a detailed physical-mathematical model To explain the mechanism that leads to the accumulation of fibers from the belly to the navel. The intrinsic characteristics of the hair, the cyclical rhythm of our breath and the ‘friction Due to the rubbing of the skin with clothes, all fundamental characteristics to reveal the secrets of this microscopic phenomenon.
The role of hair and breathing
Previous studies, such as a study conducted by dr. Steinhauser who collected and analyzed several umbilical hands samples, identified the composition of the BBL: mainly Textile fibersmix with skin cells, dust And sweat. However, no research to date had explained how these fibers end up precisely in the navel.
The new theory is based onorientation and structure of abdominal hair. The surface of the human hair is covered with scales microscopic arranged as tiles, oriented by the root towards the tip. This gives the friction and lubrication (tribological properties) to the fur): the particles movement along the direction of growth of the hair (from root to tip) meets less friction compared to the opposite one.
During breathing, the periodic movement of the abdomen generates one rubbing between skin and clothingwhich leads to the movement of the fabric fibers. When we inspire the air, the shirt flows upwards against the direction of the hairslowing down the fiber movement. Instead, when we expose, throwing the air out, the sliding takes place in the direction of the hair, promoting a clear advancement of the fibers towards the navel. This cyclical process creates a sort of “Arpione -shaped transporter“Natural: the fibers, subject to opposite forces in the two respiratory cycles, end up moving progressively towards the navel.
Experiments and mathematical model
To verify the plausibility of the mechanism, the author built a mathematical model which considers the friction forces between the hair, fiber and fabric, as well as the pressure exerted by the clothing.
The model includes:
- an estimate of the friction coefficient between fabric and hair;
- theeffect of the curvature of the abdomen on the pressure of the shirt;
- the continuous production of Pelucchi (such as “source”) due toabrasion with the fabric;
- The unidirectional transport simulated as a differential equation to a size.
The theoretical results coincide with empirical measures: A daily production of about 1 mg of BBL is expectedvalue compatible with Steinhauser’s observations.
Because not everyone produces umbilical “peluchio”
Not all navels produce plongs and the model clearly explains it. In order for fiber to pass easily from one hair to another, one is necessary sufficient density of abdominal hair. Less hair means a lower fiber transport capacity.
Protruding navel (the so -called “outies“) do not hold back the fibers because they lack the anatomical “pocket” in which the stuffed stumps are trapped. Furthermore, the bigger the abdomen, the higher the surface of fiber collection and the pressure of the fabric, thus increasing the efficiency of the storage process of stuffing in the navel.
A phenomenon with potential technological applications
As trivial as it may seem, the formation of umbilical “plongs” is actually the result of a complex game between breathing, the different friction between the directions of the hair (anisotropic friction) and the movement of the textile fibers. This study shows that even small daily mysteries can hide fascinating and useful mechanisms to inspire new technologies.
Beyond curiosity, in fact, understanding the unidirectional transport of microfibre it could inspire innovative solutions in the technological field And doctor: from the role for the removal of dust, to asymmetrical adhesive surfaces, up to the reduction of contamination from “plong” in the operating room.
