Body armor suffers from a core tension: it must be light enough so the soldier wearing it can still fight effectively, but strong enough to actually stop bullets and shrapnel. Durable, shock-absorbing Kevlar is the current standard, but it can definitely be improved upon. What if, instead of making the armor itself a liquid, researchers borrow an armor design from creatures that move through it? A team at MIT, led by mechanical engineer Stephan Rudykh, designed a flexible armor inspired by fish scales.

Scale armor is almost as old as armor itself, with numerous examples found in ancient art from Rome to China. To improve on an ancient concept, the MIT team came up with a single metric for the armor's value: protecto-flexibility (Ψ).