Ultra-Tough,\nStrong, and Defect-Tolerant Elastomers\nwith Self-Healing and Intelligent-Responsive Abilities

Abstract

Mechanical\nstrength, toughness, and defect tolerance are usually\nexclusive in most artificial materials. Herein, inspired by many biomaterials\nthat overcome this tradeoff by integrating soft and hard ingredients\nthrough elaborate structural designs, we report a facile latex-assembly\nmethod to fabricate ultra-tough, strong, and defect-tolerant elastomers.\nThe elastomers are featured by a microscopic inverse opal-mimetic\nrigid skeleton of dynamically cross-linked chitosan and a continuous\nsoft matrix of vulcanized natural rubber. Such structural design enables\nthe load-bearing capability, sacrificial property, and self-healing\nability of the skeleton, the stress redistribution and extensibility\nof the matrix, and the stiffness variation between hard and soft ingredients,\nthereby imparting the elastomers with outstanding mechanical strength\nand defect tolerance, as well as extremely high toughness of 122 KJ\nm^–2, which is even higher than that of the current\nstate-of-the-art titanium alloys. Moreover, the elastomers show prominent\nhumidity sensitivity due to the hydrophilic nature of the chitosan\nskeleton. Harnessing these advantages, we fabricate a walking robot\ntriggered by humidity variation and shoes that are able to regulate\ntemperature and humidity. The concept of designing a rigid sacrificial\nskeleton within a soft continuous matrix on the microscale is quite\ngeneral, enabling the development of high-performance and intelligent\nmaterials for emerging applications.