Scientists have designed materials that can expand in every direction at once when you stretch them, breaking a 'rule' found in every physics textbook.
April 14, 2026
Original Paper
Non-Hookean elasticity with arbitrary Poisson's ratios
arXiv · 2604.10153
The Takeaway
Standard materials get thinner when stretched, but these 'non-Hookean' models allow for arbitrary expansion properties. This allows for the creation of counterintuitive structures that could revolutionize soft robotics and impact-absorbing materials.
From the abstract
In a previous paper \cite{Itskov-MoSM} we presented a hyperelastic isotropic material model whose stress-strain response is non-linear even at infinitesimal deformations and cannot thus be linearized. As a result values of Poisson's ratio greater than one half were obtained. In this contribution, we further propose an isotropic strain energy function which is always positive-definite and depending on material constants delivers arbitrary values of Poisson's ratio (except of $-1$) in agreement wi