Kneading-Inspired Versatile Design for Biomimetic Skins with a Wide Scope of Customizable Features.

Biomimetic skins featuring customizable functions and human tissue-compatible mechanical properties have garnered tremendous interest for potential applications in human-machine interfaces, flexible wearable devices, and soft robotics. However, most existing skin-like materials require complex molecular design or multistep functionalization to achieve various functionalities that match or even surpass the performance of human skin. Thus, simultaneously minimizing production costs and achieving customizable features are still highly desirable yet challenging. Herein, inspired by a well-known kneading technique that renders a homogeneous mixture of all the ingredients, a versatile method involving two steps of kneading and resting is employed to prepare biomimetic skins with a wide scope of customizable features. Commonly used one-dimensional (1D), two-dimensional (2D), three-dimensional (3D) nanofillers and even solvents are demonstrated to be homogeneously dispersed in the viscoelastic hydrogel matrices by hand kneading, which not only contributes to improved mechanical properties and new functionalities, but also makes full use of raw materials without waste. Furthermore, similar to the combination of "condiments" in kneading dough, the flexible integration of functional fillers offers exciting and versatile platforms for the design of biomimetic skins with tunable application-specific properties, such as mechanical compliance, sensory capabilities, freezing resistance, 3D printability, fluorescence tunability, etc.