Cephalopod-Inspired Chromotropic Ionic Skin with Rapid Visual Sensing Capabilities to Multiple Stimuli.

Biological skin systems can perceive various external stimuli through ion transduction. Especially, the skin of some advanced organisms such as cephalopods can further promptly change body color by manipulating photonic nanostructures. However, the current skin-inspired soft iontronics lack the rapid full-color switching ability to respond to multiple stimuli including tension, pressure, and temperature. Here, an intelligent chromotropic iontronics with these fascinating functions is developed by constructing a biomimetic ultrastructure with anisotropic electrostatic repulsion. This skin-like chromotropic iontronics can synchronously realize electrical response and optical visualization to mechanical strain and tactile sensation by adjusting the ultrastructure in cooperation with ionic mechanotransduction. Notably, it can perform instantaneous geometric changes to thermal stimuli via an anisotropic electrostatic repulsion interior. Such a capability allows bionic skin to transduce temperature or infrared light into ionic signals and color changes in real time. The design of anisotropic photonic nanostructures expands the intelligent application for soft iontronics at higher levels, providing a concise, multifunctional, interactive sensing platform that dynamically displays stimuli information on its body.