Two-Factor Authentication Inspired Optical Security of Information Enabled by Silica Nanofibers.

Two-factor authentication (2FA) is widely used in informatics for identity verification and information encryption, yet its applications in materials science remain largely underexplored. In this study, a composite film composed of silica nanofibers (NFs) and fluorescent nanofibers (FNFs) is presented, offering a unique material-based approach to 2FA encryption. NFs and FNFs are synthesized via water-in-oil emulsions, resulting in films that can be both liquid- and light-responsive. NFs assembly exhibits intriguing light-scattering characteristics, rendering it opaque under normal conditions but transparent when wetted, functioning as a liquid-triggered optically shielding material. Embedded FNFs remain concealed within NF matrix, becoming fluorescently visible only under ultraviolet A (UVA) light illumination of specific wavelength. The encryption system requires two decryption keys - liquid and UVA light, which must be applied sequentially to successfully access the encoded information. Upon liquid exposure, the film transitions from opaque to transparent, allowing light transmission. Subsequent UVA irradiation reveals the hidden fluorescent patterns labeled by FNFs in film. This sequential encryption-decryption mechanism mimics the principles of 2FA in digital data systems, providing a promising new paradigm for secure information storage and transmission for patterns using material-based strategies.