Genetically Engineered Proteins based Nacre-like Nanocomposites with Superior Mechanical and Electrochemical Performance

The molecular engineering of proteins at atomistic scale with specific material binding units and the introduction of designed functional-linkers provides a unique approach to fabricate genetically modified high performance and responsive biomimetic composites. This work is inspired by tough biological materials, nacre, which possesses hierarchical ‘brick-mortar’ architecture containing multifunctional soft organic molecules, plays a significant role in improved mechanical properties of composites. A bio-inspired composite, using a resilin-based hybrid protein polymer with selective binding motifs for reduced graphene oxide (RGO) and nanofibrillated cellulose (NFC) was developed. The adhesive and elastic domains of fusion proteins shows synergistic effect with improvement in both strength as well as toughness of synthetic nacre. We observed that the hybrid protein could act as spacer molecule tuning the ion sorption and transport across the inter-layers of NFC/RGO depending on the processing conditions. Interestingly, the protein complexed freestanding solid-state films showed negligible internal resistance and improved supercapacitance suitable for flexible electronic devices. The protein-mediated binding of NFC and RGO reduces the resistance arising from poor electrode/electrolyte interfaces, which is difficult to achieve through conventional routes. The current biosynthetic route for engineering proteins provides a novel perspective to develop materials programmed with desired properties, depending upon targeted applications.