Insect cuticle-inspired design of sustainably sourced composite bioplastics with enhanced strength, toughness and stretch-strengthening behavior

Insect cuticles that are mainly made of chitin, chitosan and proteins provide insects with rigid, stretchable and robust skins to defend harsh external environment. The insect cuticle therefore provides inspiration for engineering biomaterials with outstanding mechanical properties but also sustainability and biocompatibility. We herein propose a design of high-performance and sustainable bioplastics via introducing CPAP3-A1, a major structural protein in insect cuticles, to specifically bind to chitosan. Simply mixing 10w/w% bioengineered CPAP3-A1 protein with chitosan enables the formation of plastics-like, sustainably sourced chitosan/CPAP3-A1 composites with significantly enhanced strength (∼90 MPa) and toughness (∼20 MJ m -3), outperforming previous chitosan-based composites and most synthetic petroleum-based plastics. Remarkably, these bioplastics exhibit a stretch-strengthening behavior similar to the training living muscles. Mechanistic investigation reveals that the introduction of CPAP3-A1 induce chitosan chains to assemble into a more coarsened fibrous network with increased crystallinity and reinforcement effect, but also enable energy dissipation via reversible chitosan-protein interactions. Further uniaxial stretch facilitates network re-orientation and increases chitosan crystallinity and mechanical anisotropy, thereby resulting in stretch-strengthening behavior. In general, this study provides an insect-cuticle inspired design of high-performance bioplastics that may serve as sustainable and bio-friendly materials for a wide range of engineering and biomedical application potentials.

Advances in decontamination of wastewater using biomass-basedcomposites: A critical review

Contaminant removal from wastewater using natural biosorbents has been widely studied as a suitable and environmentally benign alternative for conventional techniques. Currently, researchers are working on various biomass-based composites for wastewater remediation to improve the performance of natural biosorbents. This review takes into focus a wide range of biomass-based composites like hydrogel composites, metal oxide composites, magnetic composites, polymer composites, carbon nanotubes (CNTs) and graphene composites, metal organic framework composites (MOFs) and clay composites for the removal of various contaminants from wastewater. It is evident from the literature survey that the composite fabrication involves the modification of morphological and textural features of the biomass which results in significant enhancement of adsorption capacity. Apart from this, regeneration of the used biomass-based composite is also studied in depth in order to overcome the problem of solid waste generation. This review would prove to be beneficial for researchers who are currently focusing on the development of cost-effective, easily available, recyclable biomass-based composites with enhanced adsorption capacities for wastewater treatment.