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Inspired by biological systems, we report a supramolecular polymer-colloidal hydrogel (SPCH) composed of 98 wt % water that can be readily drawn into uniform (∼6-µm thick) "supramolecular fibers" at room temperature. Functionalized polymer-grafted silica nanoparticles, a semicrystalline hydroxyethyl cellulose derivative, and cucurbit[8]uril undergo aqueous self-assembly at multiple length scales to form the SPCH facilitated by host-guest interactions at the molecular level and nanofibril formation at colloidal-length scale. The fibers exhibit a unique combination of stiffness and high damping capacity (60-70%), the latter exceeding that of even biological silks and cellulose-based viscose rayon. The remarkable damping performance of the hierarchically structured fibers is proposed to arise from the complex combination and interactions of "hard" and "soft" phases within the SPCH and its constituents. SPCH represents a class of hybrid supramolecular composites, opening a window into fiber technology through low-energy manufacturing. supramolecular fiber | hydrogel | self-assembly | damping | spider silk I n nature, spiders spin silk fibers with superb properties at ambient temperatures and pressures (1, 2). We have yet to mimic such an elegant process. Conventionally, synthetic fibers are manufactured through a variety of spinning techniques, including wet, dry, gel, and electrospinning (3). Such approaches to generate fibers are limited by high energy input, laborious procedures, and intensive use of organic solvents. Supramolecular pathways enable the formation of filamentous soft materials that are showing promise in biomedical applications (4-6), such as cell culture (7-9) and tissue engineering (10). However, such materials are constrained by the length scale (submicrometer level) (11-13), energy intake during production (9), and complex design of assembly units (14).Here, we report drawing supramolecular fibers of arbitrary length from a dynamic supramolecular polymer-colloidal hydrogel (SPCH) at room temperature (Movie S1). The components consist of methyl viologen (MV)-functionalized polymer-grafted silica nanoparticles (P1), a semicrystalline polymer in the form of a hydroxyethyl cellulose derivative (H1), and cucurbit[8]uril (CB[8]) as illustrated in Fig. 1. The macrocycle CB[8] is capable of simultaneously encapsulating two guests within its cavity, forming a stable yet dynamic ternary complex, and has been exploited as a supramolecular "handcuff" to physical cross-link functional polymers (15-18). Introducing shape-persistent nanoparticles into the supramolecular hydrogel system allows for modification of the local gel structures at the colloidal-length scale, resulting in assemblies with unique emergent properties (19). The hierarchical nature of the SPCH is presented, where the hydrogel is composed of nanoscale fibrillar structures. The self-assembled SPCH composite exhibits great elasticity at a remarkably high water content (98%), showing a low-energy manufacturing process for fibers from natural, ...

From the stems of agricultural crops to the structural trunks of trees, studying the mechanical behaviour of plant stems is critical for both commerce and science. Plant scientists are also increasingly relying on mechanical test data for plant phenotyping. Yet there are neither standardized methods nor systematic reviews of current methods for the testing of herbaceous stems. We discuss the architecture of plant stems and highlight important micro- and macrostructural parameters that need to be controlled and accounted for when designing test methodologies, or that need to be understood in order to explain observed mechanical behaviour. Then, we critically evaluate various methods to test structural properties of stems, including flexural bending (two-, three-, and four-point bending) and axial loading (tensile, compressive, and buckling) tests. Recommendations are made on best practices. This review is relevant to fundamental studies exploring plant biomechanics, mechanical phenotyping of plants, and the determinants of mechanical properties in cell walls, as well as to application-focused studies, such as in agro-breeding and forest management projects, aiming to understand deformation processes of stem structures. The methods explored here can also be extended to other elongated, rod-shaped organs (e.g. petioles, midribs, and even roots).

Bamboo is a rapidly renewable material that is available globally and comparable in strength to modern structural materials. The widespread use of bamboo in construction is limited by the inherent variability in its geometric and mechanical properties, and the lack of standardisation. Engineered bamboo aims to reduce the variability of the natural material and is processed and manufactured into laminated composites. Although the composites have mechanical properties similar to other structural materials, the products are currently limited to architectural applications. A field of research on engineering bamboo is emerging with the aim to demonstrate and expand its use to structural applications. To summarise the state of the art, a review of published research is presented with the focus on two types of engineered bamboo: bamboo scrimber and laminated bamboo. The materials are compared with structural timber and laminated veneer lumber to demonstrate the potential applications and practical use.