Functionalization of structural materials through electro-blown spinning of ultrathin and transparent silk fibroin ionotronic nanofiber skin

Direct functionalization of structural materials can provide an elegant balance between their structure, performance, and function. However, effective direct functionalization techniques are very limited. This work reports a technique to functionalize structural materials in a non-destructive manner, wherein the surface of the materials is selectively etched without compromising their internal structure. In this technique, an ultrathin and transparent silk fibroin ionotronic nanofiber skin (SFINS) is spun on the surface of structural materials through electro-blown spinning, endowing them with electric conductivity and environmental responsiveness. This process is characterized by outstanding scalability, low cost, and high efficiency. In addition, the SFINS can be firmly bonded to the surface of different structural materials, such as glass, metals, polymers, and wood. More importantly, the electro-blown spinning process and the formed SFINS do not alter the structure, properties, and sustainability of the substrate materials. For instance, the transparency of glass and acrylic plates, the texture of wood, the color of plastics, the text of papers, the elasticity of elastomers, as well as their strength are all retained. Consequently, structural materials functionalized under the proposed process can be directly integrated into functional devices that require both structural stability and functional diversity in practice use. In this work, two prototypes are developed to demonstrate the applications of SFINS-functionalized structural materials as tactile receptors for an intelligent sorting manipulator and as a self-powered IntelliSensor for geological hazard early warning. Both examples reveal the advantages of the proposed technique in terms of the balance between the structure, performance, and function of the developed device systems.