Researchers have discovered that applying a localised pull to a flat, flexible sheet causes it to fold dramatically, without any pre-existing creases
A localised pull triggers a deep fold with no patterns or cuts
Researchers from the University of Birmingham, Nanyang Technological University and the University of Oxford have discovered that applying a localised pull to a flat, flexible sheet can cause it to fold dramatically—without any pre-existing creases or patterns.
This phenomenon, termed Localised Tension-induced Giant (TUG) folding, challenges the traditional understanding that materials buckle only under compression. Instead, the study reveals that a focused tensile force can induce significant out-of-plane deformations, leading to pronounced folds perpendicular to the direction of the applied tension.
"It's counterintuitive, as we usually associate folding with pushing or compressing, not pulling. But our experiments and simulations show that a localised pull can effectively 'convert' tension into compression, causing the sheet to fold."
The team employed a combination of physical experiments, computer simulations, and mathematical modelling to understand this behaviour. They found that the key lies in the geometry of the applied force: when tension is applied narrowly, it creates a stress distribution that leads to compression in the perpendicular direction, resulting in folding.
This groundbreaking work was published this week in the Proceedings of the National Academy of Sciences (PNAS) highlighting its significance to the broader scientific community.
The discovery opens up exciting opportunities in soft robotics, deployable structures, and flexible electronics. By harnessing TUG folding, engineers could design materials and devices that change shape or function in response to simple tensile inputs - turning a humble tug into a powerful actuation mechanism.
Assistant Professor
Staff profile for Dr Mingchao Liu, University of Birmingham
