Play Live Radio
Next Up:
0:00
0:00
0:00 0:00
Available On Air Stations

The physics behind the most annoying thing that could ever happen to you: A paper cut

MICHEL MARTIN, HOST:

A very different topic now - A, let me ask you this.

A MARTÍNEZ, HOST:

Yeah.

MARTIN: What do you do when you get a paper cut?

MARTÍNEZ: Oh, I - some really vile Spanish curse words (laughter).

MARTIN: OK. Well, maybe next time, you could channel Kaare Jensen, who teaches physics at the Technical University of Denmark.

KAARE JENSEN: I got a paper cut at home. I thought, this cannot be. Now I have to understand what's going on.

MARTIN: Jensen coped by designing a study, A.

MARTÍNEZ: All right, so what question did he try to answer?

MARTIN: Well, why do some types of paper cut, while others don't?

JENSEN: We consider trying to recruit subjects, but it's unethical, and it's really hard. No one volunteers.

MARTIN: So he and his colleagues got different kinds of paper - book paper, photo paper, Post-it notes - and they found a substitute for skin.

JENSEN: We built a little robot, a little ninja machine that can do the cutting. The paper can then cut into a block of ballistics gelatin, which has the same mechanical properties as your finger or the skin.

MARTÍNEZ: Yeah, that's the stuff they make the dummies out of on "MythBusters."

MARTIN: Right, right.

MARTÍNEZ: Yeah.

MARTIN: So unlike metal materials like a kitchen knife, where you want the edge to be as thin as you can get it, there's a point where paper gets too thin to cut. It's too weak. It just buckles.

MARTÍNEZ: Yeah. For example, you can't chop onions with tissue paper.

MARTIN: Of course, but you can dry the tears you cried from chopping the onions.

MARTÍNEZ: (Laughter) Yeah. So what did they find?

MARTIN: Well, they published their study in the journal Physical Review E.

JENSEN: The most hazardous paper is 65 microns thick, and that corresponds roughly to some newspapers, but also dot-matrix printer paper, which is, like, an old-fashioned type of printer. Some scientific journals, like Nature and Science - they are also quite hazardous to handle.

MARTÍNEZ: (Laughter) Old fashioned-y (ph) printers.

MARTIN: I know. Thank you for that. So the researchers also found cuts are more likely when the paper is at an angle to the skin, not straight on.

MARTÍNEZ: And they designed a paper knife that actually really works.

MARTIN: Yes.

JENSEN: We made a product that we call the paper machete. It's a little 3D-printed handle that will house scraps of paper, and we actually showed that a simple paper blade can cut into produce - fruit, chicken, apple.

MARTIN: But the paper blade only cuts once, and then it has to be replaced.

MARTÍNEZ: Unlike our fingers, Michel, which stand the test of time.

MARTIN: So true.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.

Tags
Hosts
[Copyright 2024 NPR]