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Microcapsules and microgels consisting of macromolecular networks have received increasing attention due to their biomedical and pharmaceutical applications. Protein microgels and in particular silk-based microcapsules have desirable properties due to their biocompatibility and lack of toxicity. Typically such structures formed through emulsion templating are spherical in geometry due to interfacial tension. However, approaches to synthesis particles with more complex and non-spherical geometries are sought due to their packing properties and cargo release characteristics. Here, we describe a droplet-microfluidic strategy for generating asymmetric tubular-like microgels from reconstituted silk fibroin; a major component of native silk. It was determined using fluorescence microscopy, that the shear stress within the microchannel promotes surface protein aggregation, resulting in the asymmetric morphology of the microgels. Moreover, the structural transition that the protein undergoes was confirmed using FTIR. Crucially, the core of the microgels remains liquid, while the surface has fully aggregated into a fibrillar network. Additionally, we show that microgel morphology could be controlled by varying the dispersed to continuous phase flow rates, while it was determined that the radius of curvature of the asymmetric microgels is correlated to the wall shear stress. By comparing the surface fluorescence intensity of the microgels as a function of radius of curvature, the effect of the shear stress on the amount of aggregation could be quantified. Finally, the potential use of these asymmetric microgels as carriers of cargo molecules is showcased. As the core of the microgel remains liquid but the shell has gelled, this approach is highly suitable for the storage of bio-active cargo molecules such as antibodies, making such a delivery system attractive in the context of biomedical and pharmaceutical applications.

Funder: Winton Programme for the Physics of Sustainability (PhD scholarship), When pursuing sustainable approaches to fabricate photonic structures, nature can be used as a source of inspiration for both the nanoarchitecture and the constituent materials. Although several biomaterials have been promised as suitable candidates for photonic materials and pigments, their fabrication processes have been limited to the small to medium-scale production of films. Here, by employing a substrate-free process, structurally coloured microparticles are produced via the confined self-assembly of a cholesteric cellulose nanocrystal (CNC) suspension within emulsified microdroplets. Upon drying, the droplets undergo multiple buckling events, which allow for greater contraction of the nanostructure than predicted for a spherical geometry. This buckling, combined with a solvent or thermal post-treatment, enables the production of dispersions of vibrant red, green, and blue cellulose photonic pigments. The hierarchical structure of these pigments enables the deposition of coatings with angular independent colour, offering a consistent visual appearance across a wide range of viewing angles., This work was supported by: the European Research Council ([ERC-2014-STG H2020 639088] and [ERC-2017-POC 790518] to S.V., R.P., T. Z., & B.F.-P.), the BBSRC ([David Phillips Fellowship BB/K014617/1] to S.V. and [BB/V00364X/1] to S.V. & R.P.), the EPSRC ([EP/R511675/1] to S.V. & R.P.), and the Winton Programme for the Physics of Sustainability (PhD scholarship to T.Z.).

Funder: Emil Aaltosen Säätiö (Emil Aaltonen Foundation); doi: https://doi.org/10.13039/501100004756, Funder: Philip Leverhulme Prize [PLP-2019-271]; Lord Lewis Research Studentship in Chemistry., The transfer of chirality across length-scales is an intriguing and universal natural phenomenon. However, connecting the properties of individual building blocks to the emergent features of their resulting large-scale structure remains a challenge. In this work, we investigate the origins of mesophase chirality in cellulose nanocrystal suspensions, whose self-assembly into chiral photonic films has attracted significant interest. By correlating the ensemble behaviour in suspensions and films with a quantitative morphological analysis of the individual nanoparticles, we reveal an inverse relationship between the cholesteric pitch and the abundance of laterally-bound composite particles. These bundles thus act as colloidal chiral dopants, analogous to those used in molecular liquid crystals, providing the missing link in the hierarchical transfer of chirality from the molecular to the colloidal scale.

Funder: University of Cambridge | Darwin College, University of Cambridge (Darwin); doi: https://doi.org/10.13039/501100000595, Funder: Federation of European Biochemical Societies (FEBS); doi: https://doi.org/10.13039/100012623, Funder: EC | EC Seventh Framework Programm | FP7 Ideas: European Research Council (FP7-IDEAS-ERC - Specific Programme: "Ideas" Implementing the Seventh Framework Programme of the European Community for Research, Technological Development and Demonstration Activities (2007 to 2013)); doi: https://doi.org/10.13039/100011199; Grant(s): 337969, Funder: RCUK | Biotechnology and Biological Sciences Research Council (BBSRC); doi: https://doi.org/10.13039/501100000268, The abundance of plant-derived proteins, as well as their biodegradability and low environmental impact make them attractive polymeric feedstocks for next-generation functional materials to replace current petroleum-based systems. However, efforts to generate functional materials from plant-based proteins in a scalable manner have been hampered by the lack of efficient methods to induce and control their micro and nanoscale structure, key requirements for achieving advantageous material properties and tailoring their functionality. Here, we demonstrate a scalable approach for generating mechanically robust plant-based films on a metre-scale through controlled nanometre-scale self-assembly of water-insoluble plant proteins. The films produced using this method exhibit high optical transmittance, as well as robust mechanical properties comparable to engineering plastics. Furthermore, we demonstrate the ability to impart nano- and microscale patterning into such films through templating, leading to the formation of hydrophobic surfaces as well as structural colour by controlling the size of the patterned features.

Active systems such as microorganisms and self-propelled particles show a plethora of collective phenomena, including swarming, clustering, and phase separation. Control over the propulsion direction and switchability of the interactions between the individual self-propelled units may open new avenues in designing of materials from within. Here, we present a self-propelled particle system, consisting of half-gold-coated titania (TiO2) particles, in which we can quickly and on-demand reverse the propulsion direction, by exploiting the different photocatalytic activities on both sides. We demonstrate that the reversal in propulsion direction changes the nature of the hydrodynamic interaction from attractive to repulsive and can drive the particle assemblies to undergo both fusion and fission transitions. Moreover, we show these active colloids can act as nucleation sites, and switch rapidly the interactions between active and passive particles, leading to reconfigurable assembly and disassembly. Our experiments are qualitatively described by a minimal hydrodynamic model., Nature Communications, 11 (1), ISSN:2041-1723