Environmentally responsive composite films fabricated using silk nanofibrils and silver nanowires

In this article, a natural polymeric nanomaterial, silk nanofibrils (SNFs), and a metal nanomaterial, silver nanowires (AgNWs), were used to fabricate two environmentally responsive composites using a simple and convenient vacuum filtration method, based on the unique structures of these two nanomaterials. An AgNW/SNF hybrid film is made by homogeneously dispersing AgNWs as a three-dimensional conducting network in an insulting SNF matrix. In the meantime, another type of composite film, AgNW/SNF layered film, is fabricated by forming a separate AgNW conductive layer on the top of an SNF substrate. It is found that both the composite films can be designed as environment responsive devices. The AgNW/SNF hybrid film exhibits unique humidity-sensitive conductivity, and hence can act as an effective humidity-sensing switch. On the other hand, the AgNW/SNF layered film demonstrates a combination of good transparency and conductivity. Such transparent layered films can be assembled into a pressure sensor with a low detection limit of 12 Pa and rapid response speed of less than 60 ms. Based on the sustainability, biocompatibility, and excellent skin affinity of silk protein, these AgNW/SNF composites can be a promising alternative to synthetic polymers when designing touch screens, wearable health monitoring equipment, etc.