Localized Liquefaction Coupled with Rapid Solidification for Miniaturizing/Nanotexturizing Microfibrous Bioassemblies into Robust, Liquid-Resistant Sheet

Biopolymeric fibers with microscale diameters have long been commercially used to generate network structured assemblies (paper-based products). Despite overwhelming productivity and widespread use, unconventional applications of these products are challenged by inherent imperfection related to limited internal bonding and an abundance of interfiber gaps, among other things. Here, we demonstrate the use of a green, scalable concept involving localized liquefaction and rapid solidification to miniaturize microfibrous bioassemblies into nanotextured, delicately reorganized sheets. The time for bioassembly solvent interaction was identified as a critical factor. On the surface of reorganized bioassemblies, size-tunable outgrowths were formed due to nonsolvent-induced rapid phase transition. A bioassembly-solvent contact time of 10 min resulted in surface nanostructuring. Densification of bioassemblies correlated well with the development of optical transparency. Reorganized bioassemblies exhibited pronounced mechanical robustness even after being soaked in water. Strong resistance to penetration by aqueous/nonaqueous liquids was identified. The liquid-contaminated surface of reorganized bioassemblies was easily cleanable. These features can be attributed to significant improvement of structural integrity. On the basis of the use of green, recyclable solvents/nonsolvents, the facile miniaturization of mass-producible microfibrous bioassemblies into delicately structured sheets with tunable functionalities would facilitate applications such as those related to advanced barrier packaging materials, sensors, and electronics.