Active camouflage from a polymer: Human skin is soft and compliant, but it can quickly become stiff when deformed to prevent injury. Chameleon skin can change color when the animal goes from a relaxed to an excited state. Although these properties can be captured individually in synthetic materials, the combination of different dynamic responses can be hard to control. Vatankhah-Varnosfaderani et al. created triblock copolymers of the ABA variety, where the A blocks have a linear structure and the B blocks are like bottlebrushes. When strained, these polymers stiffened like human skin and changed color, thus giving the materials a range of adaptive properties. Science , this issue p. 1509

The current approach to regulating mechanical properties of elastomeric materials is predominately based on the exploratory mixing of different polymers, solvents, and fillers—which is both inflexible in application and imprecise in property control. Here we overview a new materials design approach that harnesses well-defined molecular codes of independently controlled architectural parameters to program grand variation of mechanical “phenotypes”. This design-by-architecture approach generates a set of universal correlations between the molecular architecture and the physical behavior of elastomers. In turn, this will lead to novel solvent-free materials that closely mimic the mechanical behavior of biological tissues, ranging from soft fat tissue to firm skin, and fundamentally change high-impact technologies such as soft robotics, wearable electronics, and biomedical devices.