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.

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...

microfibrils are embedded. [10] These structures, which resemble artificial fiber-reinforced composites, deform largely along the alignment of the microfibrils, and deformation perpendicular to this reinforcement occurs less strongly. [11] This differential deformation is then transferred to macroscopic shape-shifting mechanisms such as self-winding. Self-winding is a competition between bending and twisting, which often stems from a need to release potential energy present in surface stresses, misfit strains, residual strains, thermal stresses, differential growth, shrinkage, or swelling. [12] Understanding these mechanisms is of fundamental importance to gaining insights into the design and application of helical shapes. Various works have been inspired by biological principles to generate self-winding as a response to external stimuli; however, most of them focus on the design of bilayers with mismatching properties. [11,13-15] Usually, the precursor is a flat ribbon or a straight rod formed by two layers with differential responses to stimuli. [3,16] However, simple formulation and production methods that mimic the spontaneous nature of self-coiling are still lacking. Here, we present a new fabrication approach that originates spontaneously self-winding wires upon their differential swelling in water. We apply biomimetic concepts to designing gelatin wires that are reinforced by amyloid fibrils (AFs) following principles similar to fiber-reinforced composites. Our fabrication dry-spins a single phase, thus bypassing the need for precise bilayer design and offering an easy, scalable, and sustainable alternative to more complex material designs. We employ β-lactoglobulin (BLG) to form AFs because of its rich and chiral structure. Although amyloid fibrils have promising properties, they alone cannot be processed as biopolymers because of their high rigidity and low plasticity. Therefore, we combine the plasticity of gelatin with the rigidity and versatile functionalization of AFs to produce wires that spontaneously self-wind in water. We investigate the origins of self-winding mechanisms by modeling the relative contributions of twisting and winding to the free energy. Finally, we explore the potential applications of such self-wound wires in sensors and actuators and complement our experimental results with theoretical interpretations. The wires disclosed here are, to the best of our knowledge, the first example of a system that is capable of performing as both actuator and sensor, produced entirely

G-quadruplex, assembled from a square array of guanine (G) molecules, is an important structure with crucial biological roles in vivo but also a versatile template for ordered functional materials. Although the understanding of G-quadruplex structures is the focus of numerous studies, little is known regarding the control of G-quartet stacking modes and the spontaneous orientation of G-quadruplex fibrils. Here, the effects of different metal ions and their concentrations on stacking modes of G-quartets are elucidated. Monovalent cations (typically K+) facilitate the formation of G-quadruplex hydrogels with both heteropolar and homopolar stacking modes, showing weak mechanical strength. In contrast, divalent metal ions (Ca2+, Sr2+, and Ba2+) at given concentrations can control G-quartet stacking modes and increase the mechanical rigidity of the resulting hydrogels through ionic bridge effects between divalent ions and borate. We show that for Ca2+ and Ba2+ at suitable concentrations, the assembly of G-quadruplexes results in the establishment of a mesoscopic chirality of the fibrils with a regular left-handed twist. Finally, we report the discovery of nematic tactoids self-assembled from G-quadruplex fibrils characterized by homeotropic fibril alignment with respect to the interface. We use the Frank–Oseen elastic energy and the Rapini–Papoular anisotropic surface energy to rationalize two different configurations of the tactoids. These results deepen our understanding of G-quadruplex structures and G-quadruplex fibrils, paving the way for their use in self-assembly and biomaterials.