Paper cuts can be very painful.
It’s common to get a small cut while flipping through a magazine or book. But tissue paper is unlikely to bleed. Now, scientists have explained the physics behind why some papers are more likely to rip through the skin.
Physicist Kaare Jensen was part of the team that conducted experiments to study this. They used a gelatin replica of human tissue. Jensen works at the Technical University of Denmark in Kongens Lyngby. They found that a thickness of about 65 micrometers (not quite 3 thousandths of an inch) was the sweet spot for a paper cut. (Or you could call it the painful spot!) Their findings were published on June 19 in Physical Review E.
A thin sheet of paper couldn’t be cut; instead it would bend. Thicker paper would make a dent in the gelatin but wouldn’t break its surface. Like the blade of a dull knife, it couldn’t apply enough force to a small area of material to make a hole in it.
The most dangerous paper in the test was the kind used in old-fashioned dot matrix printers. Good news for fingers everywhere: That paper isn’t used much anymore. Magazine paper came in second in the scientists’ tests.
The angle of cutting also matters. Pressing the edge of the paper straight into the gelatin is less likely to cause cuts than pressing the paper path at an angle down and up.
Progress on the cutting edge
Next, the researchers harnessed the cutting power of paper. They designed a 3-D printed tool they call the PaperMachete. When loaded with a strip of printer paper, the tool becomes a one-time use knife. The paper blade can cut cucumbers, peppers and apples. It can even cut chicken. The tool could be a low-cost option for preparing certain foods.
Next, the researchers plan to study more realistic, finger-shaped materials instead of flat sheets of gelatin, Jensen says.
No human fingers were harmed during the study. “Ideally, you’d want some test subjects. But volunteers are hard to find,” Jensen says.