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.
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