Paper cuts: small wounds, big mystery — until now. Scientists have unraveled the physics behind the dreaded paper cut, revealing why some types of paper are more likely to inflict a painful cut than others.
The (not so) ideal thickness
Through experiments using a gelatin replica of human tissue, the team discovered that thin sheets of paper like those used in napkins tend to buckle before cutting through the material. On the other hand, thicker paper like postcards was like a dull knife blade, failing to concentrate enough force into a small area, thus not cutting the gelatin.
The ideal thickness for causing a cut was found to be around 65 micrometers, found the researchers at the University of Denmark and the University of Oslo. This makes dot matrix printer paper, a relic from the past, the most hazardous. Fortunately, this type of paper is rarely used today. Magazine paper follows closely in its potential to cause cuts, which is bad news for avid readers of print media (the few of you still left).
“To explore skin-paper interactions, we designed an experiment in which a piece of paper contacts an artificial finger made from ballistic gelatin. Our experiments suggest that the paper thickness is one of the most important parameters in determining cutting efficacy. A relatively thin sheet often buckles before cutting is initiated, whereas the predominant interaction with thick sheets is indentation,” the researchers wrote in their study.
Papermachete
“Our preliminary data indicate that a successful paper cut is physically impossible outside a relatively narrow range of thicknesses for a given angle.”
The researchers also found that the angle at which paper slices through the gelatin plays a significant role. Paper pressed straight down is less likely to cut compared to paper that cleaves across and down.
Of course, the researchers had some fun with it. Armed with these results, they designed a 3-D printed tool aptly called the “Papermachete”. When loaded with a strip of standard printing paper, the device can be operated as a knife whose blade can cut through cucumber, peppers, apples, and even chicken.
Next, the researchers plan on repeating their experiments, this time on human volunteers. “Ideally you would want some test subjects, but it’s hard to find volunteers,” first author Kaare Jensen told Science News.
The findings appeared in the journal Physical Review E.
