We report simple, water-based fabrication methods based on protein self-assembly to generate 3D silk fibroin bulk materials that can be easily hybridized with water-soluble molecules to obtain multiple solid formats with predesigned functions. Controlling self-assembly leads to robust, machinable formats that exhibit thermoplastic behavior consenting material reshaping at the nanoscale, microscale, and macroscale. We illustrate the versatility of the approach by realizing demonstrator devices where large silk monoliths can be generated, polished, and reshaped into functional mechanical components that can be nanopatterned, embed optical function, heated on demand in response to infrared light, or can visualize mechanical failure through colorimetric chemistries embedded in the assembled (bulk) protein matrix. Finally, we show an enzyme-loaded solid mechanical part, illustrating the ability to incorporate biological function within the bulk material with possible utility for sustained release in robust, programmably shapeable mechanical formats.iomimicry draws inspiration from multiple material functions (e.g., antibacterial and antifouling, light manipulation, heat dissipation, water sequestration, superhydrophobicity, adhesiveness, and enhanced mechanical properties) to develop universal fabrication strategies to design new structural materials with utility in a variety of fields ranging from the biomedical, to the technological and architectural. Naturally occurring materials are generated through a bottom-up "generative" process that involves a nontrivial interplay of mechanisms acting across scales from the atomic to the macroscopic. In this context, the assembly of structural biopolymers, the fundamental building blocks of natural materials, leads to hierarchically organized architectures that impart unique functionality to the end material formats.Among the several structural proteins that have been studied, silk fibroin was recently shown to be suited for the generation of a number of biopolymer-based advanced material formats leveraging control of form (through sol-gelsolid transitions) and function (through material modification). The ability to generate functional materials based on water-based silk assembly is predicated on the control of the sol-gel-solid transitions of silk fibroin materials in ambient conditions. In Fig. 1A, the formation of 3D silk fibroin constructs is depicted through its dimensional hierarchy, from the nano-to the macroscales. Silk is extracted from natural sources (i.e., Bombyx mori cocoons) with a previously developed protocol (1) that yields a water suspension of the fibroin protein, where the protein molecules are organized in nanoscopic micelles (or nanoparticles) (top row of Fig. 1A), with an average diameter that changes as a function of concentration and molecular weight (Fig. S1).Control over the dynamics of water evaporation regulates silk-fibroin assembly at the molecular level and the endmaterial format properties. This has been previously observed for natural silk ...

Silk fibroin possesses unique properties for bio-functional optical interfaces and has been attracting increasing interest as an optical material. Here, we report on the refractive index and absorption coefficient of silk fibroin extracted from Bombyx mori, Antheraea mylitta, Samia ricini, and Antheraea assamensis. The influence of protein molecular weight, residual water content, and crystallinity on refractive index was investigated. The parameters for the Cauchy dispersion law and Urbach absorption were determined for each of the silk fibroins. By exploiting the differences in refractive index between the different fibroins, an all-protein slab waveguide was fabricated.

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A method to enhance the gold nanoparticle sensor response to weak analytes is demonstrated by pre-exposing the sensor to an analyte which elicits a strong response. This weak analyte effectively reduces the strong analyte interaction with the sensor.

Environmental contextRegular insecticide treatments on the interior of aircraft impedes the spread of mosquitos and other pests internationally, but border protection agencies lack effective tools to ensure airlines have complied. We report the first use of chemiresistor sensors to detect and identify insecticide residue on an interior aircraft surface. The method could be developed into a tool that helps lower the risk of vector-borne diseases like malaria entering international ports. AbstractAustralia and other island nations are protected from stowaway pest vectors, like mosquitos, by aircraft disinsection – spraying the airplane interior with an insecticide. It is a simple biosecurity measure that can reduce the spread of malaria, Zika and other mosquito-borne diseases. However, checking airline compliance and the efficacy of the insecticide residue is a difficult task for border protection officials, which requires either a live fly bioassay or off-site laboratory testing. Neither of these methods are ideal for the hectic schedules of airlines. As such, we propose using gold nanoparticle chemiresistor sensor arrays, to detect and identify insecticide residue on the interior surface of aircraft. We have shown that hexanethiol functionalised sensors have a limit of detection of 3 parts per billion (ppb) for permethrin in solution and have a broad dynamic range responding to concentrations up to 1000 ppb. The chemical residues of three different insecticide products were lifted off an interior aircraft surface and identified with an array of seven uniquely functionalised sensors. This is the first ever demonstration of gold nanoparticle chemiresistor sensors being used for the analysis of chemical residues. These sensors have the potential to rapidly check the efficacy of insecticide residues on aircraft surfaces.