Using reduced sericin as a green resist for precise pattern fabrication via water-based lithography.

The use of toxic resists and complex procedures has impeded the resolution and quality of micro/nanofabrication on virtually arbitrary substrates via photolithography. To fabricate a precise and high-resolution pattern, a sericin nanofilm-based coating was developed by reducing disulfide bonds and subsequently assembling sericin protein. Upon exposure to ultraviolet (UV) light, intermolecular amide bonds in sericin are cleaved through the action of a reducing agent, allowing the reduced sericin (rSer) coating to exhibit the functional ability to generate diverse geometric micro/nanopatterns through photomask-governed photolithography. The rSer film serves as a platform for the encapsulation of fluorescent molecules, enabling fluorescent micropatterns applicable in anti-counterfeiting and encryption. In addition, the patterned rSer nanofilms support biocompatible cell proliferation. With their excellent chemical stability, high-resolution geometric patterns can be transferred onto silicon substrates through chemical etching, resulting in periodic chemical etching patterns that display structural colours. Inspired by the micro/nanostructures of lotus leaves, elliptical microstructures exhibit superhydrophobic behaviour, highlighting the versatility of the rSer film for applications in semiconductors, anti-counterfeiting, smart displays, and superhydrophobic coatings.