Dynamic Photo-cross-linking of Native Silk Enables Macroscale Patterning at a Microscale Resolution.

Light-based structuring methods have shown reconstituted silk to be a versatile and appropriate material for a range of optical and biomaterial-based applications. However, without an understanding of how an unmodified, native, silk responds to photoprocessing, the full potential of this material cannot be realized. Here, we show that the use of native silk enables the production of compound patterns with improved resolution and image quality when quantitatively compared to standard reconstituted silk, which we link directly to the influence of molecular weight. Further insights into the mechanism behind silk structure development are provided through mechanical (rheological) and structural (FTIR) measurements and results show that processing can tune properties over several orders of magnitude, enabling potential replication of several soft tissue types. Finally, broadening our application perspective, this combination of mask-less lithography and native silk resulted in the fabrication of transparent optical elements for data storage and labeling.