Amyloid fibrils offer the possibility of controlling their contour length, aspect ratio, and length distribution, without affecting other structural parameters. Here we show that a fine control in the contour length distribution of β-lactoglobulin amyloid fibrils, achieved by mechanical shear stresses of different levels, translates into the organization of tactoids of different shapes and morphologies. While longer fibrils lead to highly elongated nematic tactoids in an isotropic continuous matrix, only sufficiently shortened amyloid fibrils lead to cholesteric droplets. The progressive decrease in amyloid fibrils length leads to a linear decrease of the anchoring strength and homogeneous tactoid → bipolar tactoid → cholesteric droplet transitions. Upon fibrils length increase, we first find experimentally and predict theoretically a decrease of the cholesteric pitch, before full disappearance of the cholesteric phase. The latter is understood to arise from the decrease of the energy barrier separating cholesteric and nematic phases over thermal energy for progressively longer, semiflexible fibrils.

Controlling the assembly of colloids in dispersion is a fundamental approach toward the production of functional materials. Nanocrystalline cellulose (NCC) is a charged nanoparticle whose colloidal interactions can be modulated from repulsive to attractive by increasing ionic strength. Here, we combine polarized optical microscopy, rheology, and small-angle scattering techniques to investigate (i) the concentration-driven transition from isotropic dispersion to cholesteric liquid crystals and (ii) salt-induced NCC phase transitions. In particular, we report on the formation of NCC attractive glasses containing nematic domains. At increasing NCC concentration, a structure peak was observed in small-angle X-ray scattering (SAXS) patterns. The evolution of the structure peak demonstrates the decrease in NCC interparticle distance, favoring orientational order during the isotropic–cholesteric phase transition. Small amounts of salt reduce the cholesteric volume fraction and pitch by a decrease in excluded volume. Beyond a critical salt concentration, NCC forms attractive glasses due to particle caging and reduced motility. This results in a sharp increase in viscosity and formation of viscoelastic glasses. The presence of nematic domains is suggested by the appearance of interference colors and the Cox–Merz rule failure and was confirmed by an anisotropic SAXS scattering pattern at q ranges associated with the presence of nematic domains. Thus, salt addition allows the formation of NCC attractive glasses with mechanical properties similar to those of gels while remaining optically active owed to entrapped nematic domains.

Para-nematic phases, induced by unwinding chiral helices, spontaneously relax to a chiral ground state through phase ordering dynamics that are of great interest and crucial for applications such as stimuli-responsive and biomimetic engineering. In this work, we characterize the cholesteric phase relaxation behaviors of β-lactoglobulin amyloid fibrils and cellulose nanocrystals confined into cylindrical capillaries, uncovering two different equilibration pathways. The integration of experimental measurements and theoretical predictions reveals the starkly distinct underlying mechanism behind the relaxation dynamics of β-lactoglobulin amyloid fibrils, characterized by slow equilibration achieved through consecutive sigmoidal-like steps, and of cellulose nanocrystals, characterized by fast equilibration obtained through smooth relaxation dynamics. Particularly, the specific relaxation behaviors are shown to emerge from the order parameter of the unwound cholesteric medium, which depends on chirality and elasticity. The experimental findings are supported by direct numerical simulations, allowing to establish hard-to-measure viscoelastic properties without applying magnetic or electric fields.

For each kilogram of food protein wasted, between 15 and 750 kg of CO2 end up in the atmosphere. With this alarming carbon footprint, food protein waste not only contributes to climate change but also significantly impacts other environmental boundaries, such as nitrogen and phosphorus cycles, global freshwater use, change in land composition, chemical pollution, and biodiversity loss. This contrasts sharply with both the high nutritional value of proteins, as well as their unique chemical and physical versatility, which enable their use in new materials and innovative technologies. In this review, we discuss how food protein waste can be efficiently valorized not only by reintroduction into the food chain supply but also as a template for the development of sustainable technologies by allowing it to exit the food-value chain, thus alleviating some of the most urgent global challenges. We showcase three technologies of immediate significance and environmental impact: biodegradable plastics, water purification, and renewable energy. We discuss, by carefully reviewing the current state of the art, how proteins extracted from food waste can be valorized into key players to facilitate these technologies. We furthermore support analysis of the extant literature by original life cycle assessment (LCA) examples run ad hoc on both plant and animal waste proteins in the context of the technologies considered, and against realistic benchmarks, to quantitatively demonstrate their efficacy and potential. We finally conclude the review with an outlook on how such a comprehensive management of food protein waste is anticipated to transform its carbon footprint from positive to negative and, more generally, have a favorable impact on several other important planetary boundaries.

Biological liquid crystals, such as cellulose and amyloid fibrils, show a physical behaviour difficult to predict and characterize. Here we present four different techniques to estimate the elastic constant K1, K2 and K3 for three different biological filamentous colloids.

Plastic waste production is a global challenging problem since its accumulation in the environment is causing devastating effects on the planet's ecosystem. Sustainable and green solutions are urgently needed, and this pairs with increasingly stronger regulations combined with improved ecological awareness. This study proposes a simple, scalable and water-based process to produce free-standing, transparent and flexible bioplastic films by combining amyloid fibrils with biodegradable polymers as two main building blocks. Amyloid fibrils can be obtained through denaturation and self-assembly from a broad class of food proteins found in milk, soy, and egg, for example. Whey is used here as a model protein, since it is the major by-product of dairy industries, and its valorization creates a valuable opportunity to produce sustainable, biodegradable, and environmentally friendly bioplastics perfectly integrated within a circular economy. Against this background, we highlight the sustainability superiority of these bioplastics over common plastics and bioplastic via a detailed life cycle assessment, anticipating an important role of this new class of bioplastics in mitigating the pressing plastic pollution challenge.

Chiral liquid crystals, or cholesteric phases, have been widely studied in the last decades, leading to fundamental advances and a multitude of applications and technologies. In general, the rich phenomenology of these systems depends directly on the molecular traits and conditions of the system, imposing precise symmetry to the resulting nematic field. By selecting amyloid fibrils as model filamentous chiral colloids, we report an unprecedented breadth of liquid crystalline morphologies, where up to six distinct configurations of the nematic field are observed under identical conditions. Amyloid-rich droplets show homogeneous, bipolar, radial, uniaxial chiral and radial chiral nematic fields, with additional parabolic focal conics in bulk. Variational and scaling theories allow rationalizing the experimental evidence as a subtle interplay between surface and bulk energies. Our experimental and theoretical findings deepen the understanding of chiral liquid crystals under confinement, opening to a more comprehensive exploitation of these systems in related functional materials.

The process of Liquid-Liquid Crystalline Phase Separation (LLCPS) in filamentous colloids is at the very core of multiple biological, physical and technological processes of broad significance. However, the complete theoretical...