Intuition tells us that when you make holes in a solid, it makes the solid softer. As an extreme example, think of a cellulose sponge, which is made from a material that is essentially wood. While you can only bend, stretch or compress a piece of wood with difficulty, you can easily deform a sponge, because it is highly porous. This intuition agrees with classical mechanics theory. So Rob Style from Oxford Mathematics and colleagues were surprised to find that this doesn't work for soft materials. Taking soft rubber-like solids and filling them with lots of microscopic holes, they found that the more holes, the stiffer the solid became. In fact, mathematical modelling shows that this is controlled by similar physics to that which ensures that small bubbles always stay spherical.
The results are important as they suggest that soft composites (like rubbers or gels) can have lots of new, unexpected properties. For example, if you have a soft, expensive solid, you can save material and weight by filling it with micropores without the usual loss of strength or stiffness. Cells in the body can potentially use this effect to change the large-scale properties of biological tissue like cartilage or skin. The research also demonstrates that you can use this effect to cloak small objects elastically in soft materials so that you can't feel their presence by deforming the soft material - a task which has been considered almost impossible to achieve using simple materials.