Paper cuts are a common injury that can cause significant pain and discomfort [1]. Surprisingly, the physics underpinning a thin flexible sheet of paper slicing into soft tissues remains unresolved. (Other cases, such as chess-wire cutters, have been described; e.g., [2].) In particular, the unpredictable occurrence of paper cuts, often restricted to a limited thickness range, has not been explained. Here, we visualized and quantified the motion, deformation, and stresses during paper cuts, uncovering a remarkably complex relationship between cutting, geometry, and material properties [3]. A model based on the hypothesis that competition between slicing and buckling controls the probability of initiating a paper cut was developed and successfully validated.
Our experiments revealed that competition between slicing and buckling underlies the erratic nature of paper cuts. Thin paper can’t cut because it lacks the structural integrity to resist buckling. Thick paper, in contrast, distributes the load across a large area and is also unable to cut. This explains why only paper within a narrow thickness range can cut. The most hazardous paper thickens is 65 μm, corresponding, e.g., to dot matrix paper or printed scientific journals (including Nature and Science).
Finally, we developed the Papermachete, a cost-effective paper-based scalpel based on our results. It uses scrap paper blades and can easily cut into vegetables and meat. To 3D print your own, use the files accessible here.
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Table I (Caption): "MPa" -> "GPa" (27 Aug 2024)
Kaare H. Jensen, Department of Physics, Technical University of Denmark Email: khjensen@fysik.dtu.dk Phone: +45 2231 5241
Please access the preprint, images, and videos here.
- [1] Mirsky, S., The unkindest cut, Scientific American 306, 80, 2012
- [2] Reyssat, E., Tallinen, T., Le Merrer, M., & Mahadevan, L. Slicing softly with shear. Physical review letters, 109(24), 244301, 2012
- [3] Arnbjerg-Nielsen S. F., Biviano M. D., & Jensen, K. H., Competition between slicing and buckling underlies the erratic nature of paper cuts, Physical Review E (2024) accepted preprint journal.
We are grateful to Norwid Behrnd and Keunhwan Park for providing additional examples of press coverage.
